#antiferromagnets

[jcmarchi]

Physicists magnetize a material with light

New Post has been published on https://thedigitalinsider.com/physicists-magnetize-a-material-with-light/

Physicists magnetize a material with light

MIT physicists have created a new and long-lasting magnetic state in a material, using only light.

In a study appearing today in Nature, the researchers report using a terahertz laser — a light source that oscillates more than a trillion times per second — to directly stimulate atoms in an antiferromagnetic material. The laser’s oscillations are tuned to the natural vibrations among the material’s atoms, in a way that shifts the balance of atomic spins toward a new magnetic state.

The results provide a new way to control and switch antiferromagnetic materials, which are of interest for their potential to advance information processing and memory chip technology.

In common magnets, known as ferromagnets, the spins of atoms point in the same direction, in a way that the whole can be easily influenced and pulled in the direction of any external magnetic field. In contrast, antiferromagnets are composed of atoms with alternating spins, each pointing in the opposite direction from its neighbor. This up, down, up, down order essentially cancels the spins out, giving antiferromagnets a net zero magnetization that is impervious to any magnetic pull.

If a memory chip could be made from antiferromagnetic material, data could be “written” into microscopic regions of the material, called domains. A certain configuration of spin orientations (for example, up-down) in a given domain would represent the classical bit “0,” and a different configuration (down-up) would mean “1.” Data written on such a chip would be robust against outside magnetic influence.

For this and other reasons, scientists believe antiferromagnetic materials could be a more robust alternative to existing magnetic-based storage technologies. A major hurdle, however, has been in how to control antiferromagnets in a way that reliably switches the material from one magnetic state to another.

“Antiferromagnetic materials are robust and not influenced by unwanted stray magnetic fields,” says Nuh Gedik, the Donner Professor of Physics at MIT. “However, this robustness is a double-edged sword; their insensitivity to weak magnetic fields makes these materials difficult to control.”

Using carefully tuned terahertz light, the MIT team was able to controllably switch an antiferromagnet to a new magnetic state. Antiferromagnets could be incorporated into future memory chips that store and process more data while using less energy and taking up a fraction of the space of existing devices, owing to the stability of magnetic domains.

“Generally, such antiferromagnetic materials are not easy to control,” Gedik says. “Now we have some knobs to be able to tune and tweak them.”

Gedik is the senior author of the new study, which also includes MIT co-authors Batyr Ilyas, Tianchuang Luo, Alexander von Hoegen, Zhuquan Zhang, and Keith Nelson, along with collaborators at the Max Planck Institute for the Structure and Dynamics of Matter in Germany, University of the Basque Country in Spain, Seoul National University, and the Flatiron Institute in New York.

Off balance

Gedik’s group at MIT develops techniques to manipulate quantum materials in which interactions among atoms can give rise to exotic phenomena.

“In general, we excite materials with light to learn more about what holds them together fundamentally,” Gedik says. “For instance, why is this material an antiferromagnet, and is there a way to perturb microscopic interactions such that it turns into a ferromagnet?”

In their new study, the team worked with FePS3 — a material that transitions to an antiferromagnetic phase at a critical temperature of around 118 kelvins (-247 degrees Fahrenheit).

The team suspected they might control the material’s transition by tuning into its atomic vibrations.

“In any solid, you can picture it as different atoms that are periodically arranged, and between atoms are tiny springs,” von Hoegen explains. “If you were to pull one atom, it would vibrate at a characteristic frequency which typically occurs in the terahertz range.”

The way in which atoms vibrate also relates to how their spins interact with each other. The team reasoned that if they could stimulate the atoms with a terahertz source that oscillates at the same frequency as the atoms’ collective vibrations, called phonons, the effect could also nudge the atoms’ spins out of their perfectly balanced, magnetically alternating alignment. Once knocked out of balance, atoms should have larger spins in one direction than the other, creating a preferred orientation that would shift the inherently nonmagnetized material into a new magnetic state with finite magnetization.

“The idea is that you can kill two birds with one stone: You excite the atoms’ terahertz vibrations, which also couples to the spins,” Gedik says.

Shake and write

To test this idea, the team worked with a sample of FePS3 that was synthesized by colleages at Seoul National University. They placed the sample in a vacuum chamber and cooled it down to temperatures at and below 118 K. They then generated a terahertz pulse by aiming a beam of near-infrared light through an organic crystal, which transformed the light into the terahertz frequencies. They then directed this terahertz light toward the sample.

“This terahertz pulse is what we use to create a change in the sample,” Luo says. “It’s like ‘writing’ a new state into the sample.”

To confirm that the pulse triggered a change in the material’s magnetism, the team also aimed two near-infrared lasers at the sample, each with an opposite circular polarization. If the terahertz pulse had no effect, the researchers should see no difference in the intensity of the transmitted infrared lasers.

“Just seeing a difference tells us the material is no longer the original antiferromagnet, and that we are inducing a new magnetic state, by essentially using terahertz light to shake the atoms,” Ilyas says.

Over repeated experiments, the team observed that a terahertz pulse successfully switched the previously antiferromagnetic material to a new magnetic state — a transition that persisted for a surprisingly long time, over several milliseconds, even after the laser was turned off.

“People have seen these light-induced phase transitions before in other systems, but typically they live for very short times on the order of a picosecond, which is a trillionth of a second,” Gedik says.

In just a few milliseconds, scientists now might have a decent window of time during which they could probe the properties of the temporary new state before it settles back into its inherent antiferromagnetism. Then, they might be able to identify new knobs to tweak antiferromagnets and optimize their use in next-generation memory storage technologies.

This research was supported, in part, by the U.S. Department of Energy, Materials Science and Engineering Division, Office of Basic Energy Sciences, and the Gordon and Betty Moore Foundation. 

[materialsscienceandengineering]

MIT physicists have created a new and long-lasting magnetic state in a material, using only light. In a study that will appear in Nature, the researchers report using a terahertz laser -- a light source that oscillates more than a trillion times per second -- to directly stimulate atoms in an antiferromagnetic material. The laser's oscillations are tuned to the natural vibrations among the material's atoms, in a way that shifts the balance of atomic spins toward a new magnetic state. The results provide a new way to control and switch antiferromagnetic materials, which are of interest for their potential to advance information processing and memory chip technology.

Read more.

[mpcomagnetics]

Magnetic Domains: Understanding the Foundation of Magnetism

Magnetic Domains: Understanding the Foundation of Magnetism Magnetic domains are the foundation of magnetism. In this post we’ll dive into the world of magnetic domains, and explore how they form, behave and the processes that determine their impact on magnetic materials. Understanding these will give you a deeper appreciation of how magnetism works in everyday applications. What are Magnetic…

[yani00]

Where is that post asking people to describe their gender without saying what it was. I just had a revelation.

[moonchild-in-blue]

Show Me How To Dance Forever info dump

Alright, I'm joining the research team side of tumblr and going through every element of the website / new information. A lot of what's here has been posted by others, so this is more of a compilation of things and me thinking out loud.

The Code - D O U O S V A V V M

The Shugborough Inscription is a sequence of letters – O U O S V A V V, between the letters D M on a lower plane – carved on the 18th-century Shepherd's Monument in the grounds of Shugborough Hall in Staffordshire, England, below a mirror image of Nicolas Poussin's painting the Shepherds of Arcadia (...) [about the relief] On the tomb is carved the Latin text Et in arcadia ego ("I am also in Arcadia" or "I am, even in Arcadia") The letters on the second line, D M, were commonly used on Roman tombs to stand for Dis Manibus, meaning "dedicated to the shades". (from wikipedia page)

I'm not gonna go into much detail about the whole Holy Grail thing, bevause you've all probably read this article by now. I do wanna point point out the obvious Arcadia = Eden connection:

Arcadia (Greek: Αρκαδία) refers to a vision of pastoralism and harmony with nature. The term is derived from the Greek province of the same name which dates to antiquity; the province's mountainous topography and sparse population of pastoralists later caused the word Arcadia to develop into a poetic byword for an idyllic vision of unspoiled wilderness. Arcadia is a poetic term associated with bountiful natural splendor and harmony. The 'Garden' is often inhabited by shepherds. The concept also figures in Renaissance mythology. Although commonly thought of as being in line with Utopian ideals, Arcadia differs from that tradition in that it is more often specifically regarded as unattainable. Furthermore, it is seen as a lost, Edenic form of life, contrasting to the progressive nature of Utopian desires. Greek mythology and the poetry of Theocritus inspired the Roman poet Virgil to write his Eclogues, a series of poems with references to Arcadia as the home of Pan, pipes and singing. (from wikipedia page)

And to point put what the shades in "dis manibus" mean:

In ancient Roman religion, the Manes (/ˈmeɪniːz/, Latin: mānēs, Classical Latin: [ˈmaː.neːs̠]) or Di Manes are chthonic deities sometimes thought to represent souls of deceased loved ones. They were associated with the Lares, Lemures, Genii, and Di Penates as deities (di) that pertained to domestic, local, and personal cult. They belonged broadly to the category of di inferi, "those who dwell below", the undifferentiated collective of divine dead. (from wikipedia page)

POINTING OUT that the Lares are viewed as guardians (sacred guardians if you will -> see Chokehold (I come as a blade, a sacred guardian) and the TOG poem (I am the teeth of God).

The Divide / The Choices

SPEAKING OF the TOG poem, the first email that prompts the choice of house reads "Behold, a Divide", which is very similar to " I am the line between" verse of the poem.

We are presented with two images (which I will get into it later) - House Veridian (crossed swords) and Feathered Host (a feather)

House Veridian: The House Must Endure Feathered Host: The Cycle Must Be Broken

House Veridian

Veridian is probably a reference to the colour viridian, given the symbol is green. Interestingly enough, this pigment is a "hydrated chromium(III) oxide", os an HEXAGONAL SHAPE (the same shape of the images we see on the email. ALSO. OMG YOU GUYSSSS LOOK:

It is antiferromagnetic up to 307 K, the Néel temperature

What's that you ask? WELL:

In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions.

THIS IS BLOODSPORT AND ALKALINE ALL OVER AGAIN, I'M GONNA THROW UP. VESSEL YOU BEAUTIFUL BASTARD NERD. MORE:

Chromium(III) oxide is amphoteric AKA In chemistry, an amphoteric compound (from Greek amphoteros 'both') is a molecule or ion that can react both as an acid and as a base

BITCH.

It is also used to polish BLADES! SWORDS! HMMMM!!!!!

If we think of The House as A Vessel for a god (which is basically what they are, mortal houses of worship), we can definitely see it as "I, the guardian, the fighter, the blade, must endure" . See Chokehold and Higher especially for this.

Feathered Host

I think the connection with thw TNDNBTG/ Euclid is pretty obvious. The constant imagery of angels and heaven in his lyrics, the "cycle" that is completed and repeated with those two songs. The cycle is broken, but it loops again.

You live with angels vs your wings won't find you heaven. You are the garden vs I will go back to Eden. You are far away where I can't reach you vs I will bring down heaven myself for you. Gods vs mortals vs angels. Beginning and End. Like F. Ocean said, "it's a loop. the other side of a loop it's a loop".

I think both of these choices are a very clear representation of the story that has been presented in the trilogy, but even more so in TMBTE. The dichotomy between continuing to fight, to spill blood, to be a hones and well polished tool, and the realisation of the enormity of the violence that persists. The desire for peace, the longing for simpler, more innocent times, for Eden, for Arcadia. A utopia that may only exist in dreams, long forgotten. The fields of elation now barren and sealed off.

Euclid marks the moment of breach, where there's finally a clear thread of hope. The break of the bough, the killing of the self, of the ego. But even then, there is still some attachment for the past weaved between the frayed ends. It's still the autumns leaves, do you remember me? And the final callback to TNDNBTG, the loop. An everlasting ouroboros, the venomous serpent biting its own tail, Even and The Tempter one and the same.

I find it interesting how the double-swords can mean so much. In tarot, it represents an impasse, a stalemate (the card is a blindfolded woman - see the Rain guardian - under the moon holding the two swords). It's used as a battlefield marker. In chemistry, double daggers are used to indicate the Transition State of a chemical reaction. Much to think about.

Show Me How To Dance Forever

Right so, I already made a half-assed post about the Nothing Lasts Forever to Show Me How To Dance Forever pipeline, but I'm keeping it here anyways. They have mentioned dance many times before, in the WH cover, in Aqua Regia and Ascensionism, in the interludes (where they say something about dancing with life and death both if I'm not mistaken).

Now, Aqua Regia makes a reference to Dark Signs . I'm done dancing to alarm bells // (...) I could see dark signs, alarm bells in your eyes. AND, Dark Signs has one of my most favourite lyrics, which goes: I might bend and break to my basic needs to be loved and close to somebody. WHICH WE CAN CONNECT to I Wanna Dance With Somebody (who loves me).

Which poses the question: WHAT are we dancing to? Are we giving in yet again to the need for love, and reveling in what it is a flawed and broken cadence of pleasure and pain alike? Or are we asking to be shown how to dance instead of fight, how to turn despair into tenderness. How to live this new life, a new beginning? Are we forever doomed to waltz with Death, to balance fire in the earth, or are sailing away to new ports, leaving funeral pyres behind towards a new shore, to Arcadia? MANY SUCH QUESTIONS!

The Black Flamingo

I don't know dawg. Is he Vessel? Black and tall and elegant and kinda weird?? Ridiculous wingspan??? Jk. I know some people have already talked about it, and it's potentially connected to the TOG novel (which I haven't read yet), so I'll leave that to you.

I might be missing some things but this is what I have for now. My brain hurts lmao.

[tempered-grace]

antiferromagnetism....

from wikipedia: "In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions."

yet in reverse, you were all my symmetry type shit

also someone already pointed this out, but the Neel temperature is where the thermal energy is large enough to disrupt the antiferromagnetic pattern...

and somewhere, somewhere the atoms stopped fusing

[thedarknesseater]

I don't know why I'm posting this but getting into anime made me want to get back to drawing again and I told myself id start this year and this was the first proper thing I did.

I'm swamped with schoolwork rn though so it was in the middle of learning about antiferromagnetic phase transition.

[earhartsease]

yo physicists - we were just reading about the differences in types of magnetism, and learning there are way more of them than we realised:

Diamagnetism, paramagnetism, and ferromagnetism are the three main types of magnetism seen in materials. Other types include antiferromagnetism, ferrimagnetism, superparamagnetism, and metamagnetism

but what we were trying to find out if you can help here is: is there an equivalent physics term for "is not magnetic at all"? is it just non-magnetic? or is it something-magnetic like the other words, perhaps amagnetic?

edit: it's nonmagnetic, thanks @delgrosso

[laineysbucketlist]

Paramagnetic substances such as aluminium and oxygen want me

Diamagnetic substances such as copper and carbon fear me

Antiferromagnetic materials such as chromium have a more complex relationship with me

[jcmarchi]

Researchers Achieve Breakthrough in Silicon-Compatible Magnetic Whirls - Technology Org

New Post has been published on https://thedigitalinsider.com/researchers-achieve-breakthrough-in-silicon-compatible-magnetic-whirls-technology-org/

Researchers Achieve Breakthrough in Silicon-Compatible Magnetic Whirls - Technology Org

Researchers from Oxford University’s Department of Physics have made a breakthrough in creating and designing magnetic whirls in membranes that can be seamlessly integrated with silicon.

These hurricane-like magnetic whirls, thought to move at incredible speeds of up to kilometres per second could be used as information carriers in a new generation of green and super-fast computing platforms. The findings have been published in Nature Materials.

Artistic impression of magnetic whirls, such as merons and antimerons, generated in a free-standing and flexible membrane of hematite on a silicon wafer. Image credit: Charles Godfrey and Hariom Jani / Oxford University

Traditionally, these elusive whirls could only be produced in materials that are limitedly compatible with silicon, hindering their practical application. This obstacle was overcome by developing a new form of magnetic layers that can be detached from their original crystal hosts and transferred onto any desired platform, such as a silicon wafer.

The work was led by Dr Hariom Jani from Oxford University’s Department of Physics working in Professor Paolo Radaelli’s research group, in collaboration with the National University of Singapore and the Swiss Light Source.

Dr Jani said: ‘Silicon-based computing is much too energy-inefficient for the next generation of computing applications such as full-scale AI and autonomous devices. Overcoming these challenges will require a new computing paradigm that uses fast and efficient physical phenomena to augment current technology.’

‘We have been looking at harnessing magnetic whirls in a special class of materials called antiferromagnets, which are 100-1000 times faster than modern devices. The problem to date has been that these whirls can only be created on rigid crystal templates that are incompatible with current silicon-based technology, so our goal was to figure out a way to translate these exotic whirls to silicon.’

‘To achieve this, we fabricated ultra-thin crystalline membranes of hematite (the main component of rust and thus the most abundant antiferromagnet) that extended laterally over macroscopic dimensions,’ explains Professor Radaelli. ‘Such membranes are relatively new in the world of crystalline quantum materials, and combine advantageous characteristics of both bulk 3D ceramics and 2D materials, while also being easily transferrable.’

The hematite layer was grown on top of a crystal template that was coated with a special ‘sacrificial layer’ made from a cement component. This sacrificial layer dissolved in water, separating the hematite easily from the crystal base. Finally, the free-standing hematite membrane was transferred onto silicon and several other desirable platforms.

The group developed a novel imaging technique using linearly polarised X-rays to visualise the nanoscale magnetic patterns within these membranes. This method revealed that the free-standing layers are able to host a robust family of magnetic whirls. Potentially, this could enable ultra-fast information processing.

‘One of our most exciting discoveries was the extreme flexibility of our hematite membranes,’ continues Dr Jani. ‘Unlike their rigid, ceramic-like bulk counterparts that are prone to breaking, our flexible membranes can be twisted, bent, or curled into various shapes without fracturing. We exploited this newfound flexibility to design magnetic whirls in three dimensions, something that was previously not possible. In the future, the shape of these membranes could be tweaked to realise completely new whirls in 3D magnetic circuits.’

The group are now working on developing prototype devices that will use electrical currents to excite the rich dynamics of these super-fast whirls. Dr Jani concludes: ‘Eventually, such devices could be integrated into new types of computers that work more like the human brain – we are very excited about what’s coming next.’

Source: University of Oxford

You can offer your link to a page which is relevant to the topic of this post.

[materialsscienceandengineering]

Currents Control Spiral Spin Structures

The demonstration that helical spin arrangements can be manipulated using electric currents holds promise for spin-based electronics. [...] In so-called spintronic devices, which have applications in communications and computing, information is encoded in patterns formed by electron spins. For efficient device operation, these spin patterns typically need to be manipulated using electric currents. Such electrical control has been demonstrated for certain spin patterns but not for helix-shaped ones, which have potentially useful features including chirality and collective dynamics. Now Je-Geun Park at Seoul National University, South Korea, and his colleagues have achieved electrical control of helical spin patterns and uncovered the mechanism behind this control [1].

Read more.

[tarragonblack1235813213455]

THE UNIVERSE OF SPACE SCIENCE

ASTRONOMY

This galaxy of space science is interested in how stars, planets, and space, basically everything else outside of Earth, operate.

We can divide ASTRONOMY into several solar systems:

ASTROMETRY:

The solar system of astronomy that has an interest in mapping celestial bodies.

THE WORLD(S) OF ASTROMETRY:

☆EXOPLANETOLOGY

This world of astrometry is interested in the number of planets that exist outside our solar system. And where these are located.

ASTROBIOLOGY

This solar system of astronomy is searching for life everywhere else, but Earth.

THE WORLD(S) OF ASTROBIOLOGY:

☆EXOBIOLOGY

This world of astrobiology has an interest in examining the possibility for life to be found and its location in space.

ASTROCHEMISTRY

This solar system of astronomy has an interest in any substance inside a celestial body, star, or a part of interstellar space.

ASTROPHYSICS

This solar system of astronomy will have an interest in the physical laws applied in outer space.

THE WORLD(S) OF ASTROPHYSICS:

☆COSMOLOGY

This world of astrophysics will be interested in the creation, evolution, and fate of the universe.

☆SPECTROSCOPY

This world of astrophysics will be interested in the reflection, absorption, and transference of light between matter.

SOLAR SCIENCE is the moon orbiting the world of astrophysics

*HELIOPHYSICS

This asteroid of solar science will be interested in the sun’s radiation and its effect in the surrounding space.

*HELIOSEISMOLOGY

This asteroid of solar science will be interested in the interior of the Sun, given away from the observation of an oscillation.

SPACE DUST WITHIN HELIOSEISMOLOGY:

1. GLOBAL HELIOSEISMOLOGY is the space dust of helioseismology that will be interested in the study of the Sun's resonant mode.

2. LOCAL HELIOSEISMOLOGY is the space dust of helioseismology that will be interested in the study of the propagation of the component wave near the Sun's surface.

THE WORLD(S) OF ASTROPHYSICS (Continued):

☆ASTEROSEISMOLOGY

This world of astrophysics will be interested in the internal structure of any star through the observation of its oscillation cycle.

☆PHOTOMETRY

This world of astrophysics will be interested in the luminosity of an astronomical object in space based on its electromagnetic radiation.

THE SPECIALIZATION(S) OF ASTROPHYSICS ARE:

1. ATOMIC PHYSICS

Atomic physics is a discipline within astrophysics that will study the atomic structure and the interaction between separate atoms.

2. NUCLEAR PHYSICS

Nuclear physics is a discipline within astrophysics that will study a proton and a neutron at the center of an atom and the interactions that hold them together in a space just a few femtometres across.

3. CONDENSED-MATTER

The study of CONDENSED MATTER is a discipline within astrophysics that will focus on the macroscopic and microscopic physical properties of matter, especially the solid and liquid phase that will arise from electromagnetic forces between atoms. More generally, the subject will study the condensed phase of matter: a system of many constituents with strong interactions among them. A more exotic condensed phase will include the superconducting phase exhibited by certain materials at an extremely low cryogenic temperature, the ferromagnetic and antiferromagnetic phase of spins on crystal lattices of atoms, and the Bose–Einstein condensate found in below freezing atomic systems.

4. PLASMA

The study of PLASMA is a discipline within astrophysics that will examine almost all of the observable matter in the universe found in the plasma state. Formed at high temperature, plasma consists of freely moving ions and free electrons. It is often called the “fourth state of matter” because its unique physical properties distinguish it from a solid, liquid, and gas. Plasma densities and temperatures vary widely, from the cold gases of interstellar space to the extraordinarily hot, dense cores of stars. Plasma densities range from those in a high vacuum with only a few particles inside a volume of 1 cubic centimeter to 1,000 times the density of a solid.

5. SUPER-FLUIDITY

The study of SUPER-FLUIDITY is a discipline within astrophysics that will examine the characteristic property of a fluid with zero viscosity, which could flow without any loss of kinetic energy.

6. GENERAL RELATIVITY

The study of GENERAL RELATIVITY is a discipline within astrophysics that will examine GRAVITY, a fundamental force in the universe. Gravity does define macroscopic behavior, which will describe large-scale physical phenomena. General relativity does, however, follow from Einstein’s principle of equivalence: on a local scale. It is impossible to distinguish between a physical effect due to gravity and those due to acceleration. Gravity is regarded as a geometric phenomenon that could arise from the curvature of space-time.

7. QUANTUM-FIELD THEORY

8. STRING THEORY

ASTROGEOLOGY

This solar system of astronomy will have an interest in the study of rocks, terrain, and material in space.

THE WORLD(S) OF ASTROGEOLOGY:

☆EXOGEOLOGY

This world of astrogeology will study how geology would relate to celestial bodies like moons, asteroids, meteorites, and comets.

☆SELENOGRAPHY

This world of astrogeology will study how any physical feature on the moon formed, such as the lunar maria, craters, and the range of mountains.

[islamiccareer]

Altermagnetism: A New Era in Magnetism Confirmed by Scientists

Magnetism has fascinated scientists and engineers for centuries, leading to groundbreaking technological advancements. From simple compass needles to complex data storage devices, magnetism plays an essential role in modern life. Until recently, physicists recognized two fundamental types of magnetism: ferromagnetism and antiferromagnetism. However, a newly confirmed third form—altermagnetism—is set to revolutionize our understanding of magnetic materials.

In this article, we will explore what altermagnetism is, how it was discovered, and why it matters for future technologies. Whether you’re a science enthusiast or someone curious about cutting-edge research, this article will provide a comprehensive and engaging explanation.

[govindhtech]

Learning Haldane Phase on Qudit-Based Quantum Processor

Haldane Stage

Topological Haldane Phase with Qudit Quantum Processor Symmetry Protection

Scientists constructed and investigated the spin-1 Haldane phase on a qudit quantum processor using trapped-ion qutrits, a major  quantum computing achievement. This breakthrough allows higher-dimensional quantum phases of matter to be natively realised, which are challenging to explore using typical qubit systems or classical methods due to their complexity and quantum nature.

Symmetry-protected topological (SPT) phases, a new condensed matter physics paradigm, use topological notions for improved metrology, durable quantum information, and innovative materials. Haldane phase, with the spin-1 Heisenberg chain, is a standard SPT phase. In this phase, integer-spin chains are classic SPT states with fascinating condensed matter and quantum information properties, unlike their half-integer spin counterparts.

Trapped-ion qudits could be used to natively study high-dimensional spin systems, according to Alpine Quantum Technologies GmbH and Universität Innsbruck researchers. Spin-1 chains in the Haldane phase are directly engineered using this technology. The researchers say their direct simulation lets them “observe not only the characteristic long-range order and short-range correlations, but also the fractionalisation of fundamental spin-1 particles into effective spin-1/2 degrees of freedom,” a system feature.

Significant study findings and successes include:

The researchers developed a scalable, predictable procedure to prepare the Affleck-Kennedy-Lieb-Tasaki (AKLT) state, a key Haldane phase state. After initialising N qutrits and an ancilla qubit into a product state, the ancilla is attached to each qutrit. This approach requires only 2N entangling gates and removes probabilistic post-selection when used with ancilla measurement feed-forward. Better than earlier qubit-based encodings, which often relied on probabilistically projecting onto a spin-1 subspace, this greatly reduces the allowed measurements for longer chains.

To verify topological features:

Long-Range String Order: Despite short-range correlations and a finite correlation length, the scientists confirmed the AKLT state's concealed antiferromagnetic order, implying a finite energy gap above its ground state. This required measuring a non-local string order parameter. This value was always non-zero, which is essential for SPT states without pairwise correlations and local order.

Spin Fractionalisation and Edge States: Open-boundary chains' symmetry protection induces fascinating quantum number fractionalisation. The researchers found that the physical spin-1 degrees of freedom fractionalise into two unpaired spin-1/2 degrees of freedom at the chain endpoints. This creates a four-fold degenerate ground-state subspace, unlike the unique ground state with closed bounds. Using edge-localized operators to drive Rabi flops showed the presence of these effective qubits. The contrast stayed nearly constant as chain length increased, confirming localisation.

The investigation revealed the Haldane SPT phase's bulk-edge link. The Haldane phase is resilient to global rotations because a global bulk operator is equal to an edge-unitary when constrained to the ground-state manifold.

Quantum Resource Efficiency: The native qudit implementation avoids probabilistic post-selection, d-dimensional spin-qubit encoding and decoding, and a lot of quantum resource overhead. This hardware-efficient technology enables many more quantum modelling applications of non-classical phases of matter.

Sequential coupling via an ancilla qudit can generate matrix product states (MPS) beyond the AKLT state. Because the trapped-ion platform may readily change the ancilla qudit's dimension (d), binding dimensions up to D=7 or more with diverse ion species are feasible. D is the possible bond dimension. Trapped-ion systems are all-to-all connected, hence the coupling order is governed by the application order of unitaries rather than the physical geometry, allowing for arbitrary MPS geometries.

The researchers also investigated the spin-1/2 cluster state, which is similar to the AKLT state. They generated this state experimentally using spin-1/2 trapped-ion qubits and found similar long-range order, short-range correlations, and edge manipulation of an effective qubit to support the bulk-edge correspondence.

This work lays the framework for future research into multidimensional SPT phases to better understand realistic condensed matter systems and materials. Quantum simulations are expected to be necessary for understanding and simulating 2D and 3D models.

[sunaleisocial]

Physicists observe a new form of magnetism for the first time

New Post has been published on https://sunalei.org/news/physicists-observe-a-new-form-of-magnetism-for-the-first-time/

Physicists observe a new form of magnetism for the first time

MIT physicists have demonstrated a new form of magnetism that could one day be harnessed to build faster, denser, and less power-hungry “spintronic” memory chips.

The new magnetic state is a mash-up of two main forms of magnetism: the ferromagnetism of everyday fridge magnets and compass needles, and antiferromagnetism, in which materials have magnetic properties at the microscale yet are not macroscopically magnetized.

Now, the MIT team has demonstrated a new form of magnetism, termed “p-wave magnetism.”

Physicists have long observed that electrons of atoms in regular ferromagnets share the same orientation of “spin,” like so many tiny compasses pointing in the same direction. This spin alignment generates a magnetic field, which gives a ferromagnet its inherent magnetism. Electrons belonging to magnetic atoms in an antiferromagnet also have spin, although these spins alternate, with electrons orbiting neighboring atoms aligning their spins antiparallel to each other. Taken together, the equal and opposite spins cancel out, and the antiferromagnet does not exhibit macroscopic magnetization.

The team discovered the new p-wave magnetism in nickel iodide (NiI2), a two-dimensional crystalline material that they synthesized in the lab. Like a ferromagnet, the electrons exhibit a preferred spin orientation, and, like an antiferromagnet, equal populations of opposite spins result in a net cancellation. However, the spins on the nickel atoms exhibit a unique pattern, forming spiral-like configurations within the material that are mirror-images of each other, much like the left hand is the right hand’s mirror image.

What’s more, the researchers found this spiral spin configuration enabled them to carry out “spin switching”: Depending on the direction of spiraling spins in the material, they could apply a small electric field in a related direction to easily flip a left-handed spiral of spins into a right-handed spiral of spins, and vice-versa.

The ability to switch electron spins is at the heart of “spintronics,” which is a proposed alternative to conventional electronics. With this approach, data can be written in the form of an electron’s spin, rather than its electronic charge, potentially allowing orders of magnitude more data to be packed onto a device while using far less power to write and read that data.   

“We showed that this new form of magnetism can be manipulated electrically,” says Qian Song, a research scientist in MIT’s Materials Research Laboratory. “This breakthrough paves the way for a new class of ultrafast, compact, energy-efficient, and nonvolatile magnetic memory devices.”

Song and his colleagues published their results May 28 in the journal Nature. MIT co-authors include Connor Occhialini, Batyr Ilyas, Emre Ergeçen, Nuh Gedik, and Riccardo Comin, along with Rafael Fernandes at the University of Illinois Urbana-Champaign, and collaborators from multiple other institutions.

Connecting the dots

The discovery expands on work by Comin’s group in 2022. At that time, the team probed the magnetic properties of the same material, nickel iodide. At the microscopic level, nickel iodide resembles a triangular lattice of nickel and iodine atoms. Nickel is the material’s main magnetic ingredient, as the electrons on the nickel atoms exhibit spin, while those on iodine atoms do not.

In those experiments, the team observed that the spins of those nickel atoms were arranged in a spiral pattern throughout the material’s lattice, and that this pattern could spiral in two different orientations.

At the time, Comin had no idea that this unique pattern of atomic spins could enable precise switching of spins in surrounding electrons. This possibility was later raised by collaborator Rafael Fernandes, who along with other theorists was intrigued by a recently proposed idea for a new, unconventional, “p-wave” magnet, in which electrons moving along opposite directions in the material would have their spins aligned in opposite directions.

Fernandes and his colleagues recognized that if the spins of atoms in a material form the geometric spiral arrangement that Comin observed in nickel iodide, that would be a realization of a “p-wave” magnet. Then, when an electric field is applied to switch the “handedness” of the spiral, it should also switch the spin alignment of the electrons traveling along the same direction.

In other words, such a p-wave magnet could enable simple and controllable switching of electron spins, in a way that could be harnessed for spintronic applications.

“It was a completely new idea at the time, and we decided to test it experimentally because we realized nickel iodide was a good candidate to show this kind of p-wave magnet effect,” Comin says.

Spin current

For their new study, the team synthesized single-crystal flakes of nickel iodide by first depositing powders of the respective elements on a crystalline substrate, which they placed in a high-temperature furnace. The process causes the elements to settle into layers, each arranged microscopically in a triangular lattice of nickel and iodine atoms.

“What comes out of the oven are samples that are several millimeters wide and thin, like cracker bread,” Comin says. “We then exfoliate the material, peeling off even smaller flakes, each several microns wide, and a few tens of nanometers thin.”

The researchers wanted to know if, indeed, the spiral geometry of the nickel atoms’s spins would force electrons traveling in opposite directions to have opposite spins, like what Fernandes expected a p-wave magnet should exhibit. To observe this, the group applied to each flake a beam of circularly polarized light — light that produces an electric field that rotates in a particular direction, for instance, either clockwise or counterclockwise.

They reasoned that if travelling electrons interacting with the spin spirals have a spin that is aligned in the same direction, then incoming light, polarized in that same direction, should resonate and produce a characteristic signal. Such a signal would confirm that the traveling electrons’ spins align because of the spiral configuration, and furthermore, that the material does in fact exhibit p-wave magnetism.

And indeed, that’s what the group found. In experiments with multiple nickel iodide flakes, the researchers directly observed that the direction of the electron’s spin was correlated to the handedness of the light used to excite those electrons. Such is a telltale signature of p-wave magnetism, here observed for the first time.

Going a step further, they looked to see whether they could switch the spins of the electrons by applying an electric field, or a small amount of voltage, along different directions through the material. They found that when the direction of the electric field was in line with the direction of the spin spiral, the effect switched electrons along the route to spin in the same direction, producing a current of like-spinning electrons.

“With such a current of spin, you can do interesting things at the device level, for instance, you could flip magnetic domains that can be used for control of a magnetic bit,” Comin explains. “These spintronic effects are more efficient than conventional electronics because you’re just moving spins around, rather than moving charges. That means you’re not subject to any dissipation effects that generate heat, which is essentially the reason computers heat up.”

“We just need a small electric field to control this magnetic switching,” Song adds. “P-wave magnets could save five orders of magnitude of energy. Which is huge.”

“We are excited to see these cutting-edge experiments confirm our prediction of p-wave spin polarized states,” says Libor Šmejkal, head of the Max Planck Research Group in Dresden, Germany, who is one of the authors of the theoretical work that proposed the concept of p-wave magnetism but was not involved in the new paper. “The demonstration of electrically switchable p-wave spin polarization also highlights the promising applications of unconventional magnetic states.”

The team observed p-wave magnetism in nickel iodide flakes, only at ultracold temperatures of about 60 kelvins.

“That’s below liquid nitrogen, which is not necessarily practical for applications,” Comin says. “But now that we’ve realized this new state of magnetism, the next frontier is finding a material with these properties, at room temperature. Then we can apply this to a spintronic device.”

This research was supported, in part, by the National Science Foundation, the Department of Energy, and the Air Force Office of Scientific Research.

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Observation of three-dimensional spin-wave interference. Girardi, Davide & Finizio, Simone & Donnelly, Claire & Rubini, Guglielmo & Mayr, Sina & Levati, Valerio & Cuccurullo, Simone & Maspero, Federico & Raabe, Jörg & Petti, Daniela & Albisetti, Edoardo. (2023). Three-dimensional spin-wave dynamics, localization and interference in a synthetic antiferromagnet. 10.48550/arXiv.2306.15404.