Spin Nernst Effect

Last updated

The spin Nernst effect is a phenomenon of spin current generation caused by the thermal flow of electrons or magnons in condensed matter. Under a thermal drive such as temperature gradient or chemical potential gradient, spin-up and spin-down carriers can flow perpendicularly to the thermal current and towards opposite directions without the application of a magnetic field. This effect is similar to the spin Hall effect, where a pure spin current is induced by an electrical current. The spin Nernst effect can be detected by the spatial separation of opposite spin species, typically in the form of spin polarization (imbalanced spin accumulation) on the transverse boundaries of a material.

The spin Nernst effect of electrons was first experimentally observed in 2016 and published by two independent groups in 2017. [1] [2]

The spin Nernst effect of magnons (quanta of spin wave excitations) was theoretically proposed in 2016 [3] [4] in collinear antiferromagnetic materials, but its experimental confirmation remains elusive. In 2017, around the same time when its electronic counterpart was experimentally observed, the spin Nernst effect of magnons was first claimed in transition metal trichalcogenide MnPS3. [5] However, the experiment involved ambiguities that cannot convincingly verify the spin Nernst effect of magnons, awaiting further experimental studies. With a more accurate description accounting for real device geometry, it was believed that optical detection should be more reliable than electronic detection. [6] At present, optical detection of the spin Nernst effect of magnons has not been reported.

See also

Related Research Articles

Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter.

Spintronics, also known as spin electronics, is the study of the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-state devices. The field of spintronics concerns spin-charge coupling in metallic systems; the analogous effects in insulators fall into the field of multiferroics.

A Bell test, also known as Bell inequality test or Bell experiment, is a real-world physics experiment designed to test the theory of quantum mechanics in relation to Albert Einstein's concept of local realism. Named for John Stewart Bell, the experiments test whether or not the real world satisfies local realism, which requires the presence of some additional local variables to explain the behavior of particles like photons and electrons. As of 2015, all Bell tests have found that the hypothesis of local hidden variables is inconsistent with the way that physical systems behave.

<span class="mw-page-title-main">Magnon</span> Spin 1 quasiparticle; quantum of a spin wave

A magnon is a quasiparticle, a collective excitation of the spin structure of an electron in a crystal lattice. In the equivalent wave picture of quantum mechanics, a magnon can be viewed as a quantized spin wave. Magnons carry a fixed amount of energy and lattice momentum, and are spin-1, indicating they obey boson behavior.

<span class="mw-page-title-main">Nernst effect</span>

In physics and chemistry, the Nernst effect is a thermoelectric phenomenon observed when a sample allowing electrical conduction is subjected to a magnetic field and a temperature gradient normal (perpendicular) to each other. An electric field will be induced normal to both.

Multiferroics are defined as materials that exhibit more than one of the primary ferroic properties in the same phase:

<span class="mw-page-title-main">Mott insulator</span> Materials classically predicted to be conductors, that are actually insulators

Mott insulators are a class of materials that are expected to conduct electricity according to conventional band theories, but turn out to be insulators. These insulators fail to be correctly described by band theories of solids due to their strong electron–electron interactions, which are not considered in conventional band theory. A Mott transition is a transition from a metal to an insulator, driven by the strong interactions between electrons. One of the simplest models that can capture Mott transition is the Hubbard model.

Spin pumping is the dynamical generation of pure spin current by the coherent precession of magnetic moments, which can efficiently inject spin from a magnetic material into an adjacent non-magnetic material. The non-magnetic material usually hosts the spin Hall effect that can convert the injected spin current into a charge voltage easy to detect. A spin pumping experiment typically requires electromagnetic irradiation to induce magnetic resonance, which converts energy and angular momenta from electromagnetic waves to magnetic dynamics and then to electrons, enabling the electronic detection of electromagnetic waves. The device operation of spin pumping can be regarded as the spintronic analog of a battery.

The spin Hall effect (SHE) is a transport phenomenon predicted by Russian physicists Mikhail I. Dyakonov and Vladimir I. Perel in 1971. It consists of the appearance of spin accumulation on the lateral surfaces of an electric current-carrying sample, the signs of the spin directions being opposite on the opposing boundaries. In a cylindrical wire, the current-induced surface spins will wind around the wire. When the current direction is reversed, the directions of spin orientation is also reversed.

<span class="mw-page-title-main">Spin echo</span> Response of spin to electromagnetic radiation

In magnetic resonance, a spin echo or Hahn echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) make use of this effect.

<span class="mw-page-title-main">122 iron arsenide</span>

The 122 iron arsenide unconventional superconductors are part of a new class of iron-based superconductors. They form in the tetragonal I4/mmm, ThCr2Si2 type, crystal structure. The shorthand name "122" comes from their stoichiometry; the 122s have the chemical formula AEFe2Pn2, where AE stands for alkaline earth metal (Ca, Ba Sr or Eu) and Pn is pnictide (As, P, etc.). These materials become superconducting under pressure and also upon doping. The maximum superconducting transition temperature found to date is 38 K in the Ba0.6K0.4Fe2As2. The microscopic description of superconductivity in the 122s is yet unclear.

<span class="mw-page-title-main">Subir Sachdev</span> Indian physicist

Subir Sachdev is Herchel Smith Professor of Physics at Harvard University specializing in condensed matter. He was elected to the U.S. National Academy of Sciences in 2014, and received the Lars Onsager Prize from the American Physical Society and the Dirac Medal from the ICTP in 2018. He was a co-editor of the Annual Review of Condensed Matter Physics from 2017–2019.

In condensed matter physics, a quantum spin liquid is a phase of matter that can be formed by interacting quantum spins in certain magnetic materials. Quantum spin liquids (QSL) are generally characterized by their long-range quantum entanglement, fractionalized excitations, and absence of ordinary magnetic order.

<span class="mw-page-title-main">Time crystal</span> Structure that repeats in time; a novel type or phase of non-equilibrium matter

In condensed matter physics, a time crystal is a quantum system of particles whose lowest-energy state is one in which the particles are in repetitive motion. The system cannot lose energy to the environment and come to rest because it is already in its quantum ground state. Because of this, the motion of the particles does not really represent kinetic energy like other motion; it has "motion without energy". Time crystals were first proposed theoretically by Frank Wilczek in 2012 as a time-based analogue to common crystals – whereas the atoms in crystals are arranged periodically in space, the atoms in a time crystal are arranged periodically in both space and time. Several different groups have demonstrated matter with stable periodic evolution in systems that are periodically driven. In terms of practical use, time crystals may one day be used as quantum computer memory.

In solid-state physics, the kagome metal or kagome magnet is a type of ferromagnetic quantum material. The atomic lattice in a kagome magnet has layered overlapping triangles and large hexagonal voids, akin to the kagome pattern in traditional Japanese basket-weaving. This geometry induces a flat electronic band structure with Dirac crossings, in which the low-energy electron dynamics correlate strongly.

In condensed matter physics, the quantum dimer magnet state is one in which quantum spins in a magnetic structure entangle to form a singlet state. These entangled spins act as bosons and their excited states (triplons) can undergo Bose-Einstein condensation (BEC). The quantum dimer system was originally proposed by Matsubara and Matsuda as a mapping of the lattice Bose gas to the quantum antiferromagnet. Quantum dimer magnets are often confused as valence bond solids; however, a valence bond solid requires the breaking of translational symmetry and the dimerizing of spins. In contrast, quantum dimer magnets exist in crystal structures where the translational symmetry is inherently broken. There are two types of quantum dimer models: the XXZ model and the weakly-coupled dimer model. The main difference is the regime in which BEC can occur. For the XXZ model, the BEC occurs upon cooling without a magnetic field and manifests itself as a symmetric dome in the field versus temperature phase diagram centered about H = 0. The weakly-coupled dimer model does not magnetically order in zero magnetic field, but instead orders upon the closing of the spin gap, where the BEC regime begins and is a dome centered at non-zero field.

Many-body localization (MBL) is a dynamical phenomenon occurring in isolated many-body quantum systems. It is characterized by the system failing to reach thermal equilibrium, and retaining a memory of its initial condition in local observables for infinite times.

Magnetic 2D materials or magnetic van der Waals materials are two-dimensional materials that display ordered magnetic properties such as antiferromagnetism or ferromagnetism. After the discovery of graphene in 2004, the family of 2D materials has grown rapidly. There have since been reports of several related materials, all except for magnetic materials. But since 2016 there have been numerous reports of 2D magnetic materials that can be exfoliated with ease just like graphene.

<span class="mw-page-title-main">Gang Cao</span> American physicist

Gang Cao is an American condensed matter physicist, academic, author, and researcher. He is a professor of physics at the University of Colorado Boulder. and Director of Center for Experiments on Quantum Materials.

<span class="mw-page-title-main">Je-geun Park</span> South Korean physicist (born 1965)

Je-Geun Park is a physicist in the Republic of Korea. He is a condensed matter physicist known for his work on wide-ranging problems of magnetism, in particular strongly correlated electron systems. He is credited with discovering a new class of magnetic 2D materials, also known as van der Waals magnets. He has worked as a professor at Seoul National University.

References

  1. Sheng, Peng; Sakuraba, Yuya; Lau, Yong-Chang; Takahashi, Saburo; Mitani, Seiji; Hayashi, Masamitsu (2017). "The spin Nernst effect in tungsten". Science Advances. American Association for the Advancement of Science (AAAS). 3 (11): e1701503. arXiv: 1607.06594 . Bibcode:2017SciA....3E1503S. doi: 10.1126/sciadv.1701503 . ISSN   2375-2548. PMC   5669613 . PMID   29119140.
  2. Meyer, S.; Chen, Y.-T.; Wimmer, S.; Althammer, M.; Wimmer, T.; Schlitz, R.; Geprägs, S.; Huebl, H.; Ködderitzsch, D.; Ebert, H.; Bauer, G. E. W.; Gross, R.; Goennenwein, S. T. B. (11 September 2017). "Observation of the spin Nernst effect". Nature Materials. Springer Nature. 16 (10): 977–981. arXiv: 1607.02277 . Bibcode:2017NatMa..16..977M. doi:10.1038/nmat4964. ISSN   1476-1122. PMID   28892056. S2CID   5050523.
  3. Cheng, Ran; Okamoto, Satoshi; Xiao, Di (2016-11-15). "Spin Nernst Effect of Magnons in Collinear Antiferromagnets". Physical Review Letters. 117 (21): 217202. arXiv: 1606.01952 . doi:10.1103/PhysRevLett.117.217202.
  4. Zyuzin, Vladimir A.; Kovalev, Alexey A. (2016-11-15). "Magnon Spin Nernst Effect in Antiferromagnets". Physical Review Letters. 117 (21): 217203. arXiv: 1606.03088 . doi: 10.1103/PhysRevLett.117.217203 .
  5. Shiomi, Y.; Takashima, R.; Saitoh, E. (2017-10-25). "Experimental evidence consistent with a magnon Nernst effect in the antiferromagnetic insulator ${\mathrm{MnPS}}_{3}$". Physical Review B. 96 (13): 134425. arXiv: 1706.03978 . doi:10.1103/PhysRevB.96.134425.
  6. Zhang, Hantao; Cheng, Ran (2022-02-28). "A perspective on magnon spin Nernst effect in antiferromagnets". Applied Physics Letters. 120 (9): 090502. arXiv: 2201.01907 . doi:10.1063/5.0084359. ISSN   0003-6951.