Condensed Matter Physics Commons^™

Surface Termination And Schottky-Barrier Formation Of In4Se3(001), Archit Dhingra, Pavlo V. Galiy, Lu Wang, Nataliia S. Vorobeva, Alexey Lipatov, Angel Torres, Taras M. Nenchuk, Simeon J. Gilbert, Alexander Sinitskii, Andrew J. Yost, Wai-Ning Mei, Keisuke Fukutani, Jia Shiang Chen, Peter Dowben

Peter Dowben Publications

The surface termination of In₄Se₃(001) and the interface of this layered trichalcogenide, with Au, was examined using x-ray photoemission spectroscopy. Low energy electron diffraction indicates that the surface is highly crystalline, but suggests an absence of C2v mirror plane symmetry. The surface termination of the In₄Se₃(001 is found, by angle-resolved x-ray photoemission spectroscopy, to be In, which is consistent with the observed Schottky barrier formation found with this n-type semiconductor. Transistor measurements confirm earlier results from photoemission, suggesting that In₄Se₃(001 is an n-type semiconductor, so that Schottky barrier …

Perspective: Ferromagnetic Liquids, Robert Streubel, Xubo Liu, Xuefei Wu, Thomas P. Russell

Robert Streubel Papers

Mechanical jamming of nanoparticles at liquid-liquid interfaces has evolved into a versatile approach to structure liquids with solid-state properties. Ferromagnetic liquids obtain their physical and magnetic properties, including a remanent magnetization that distinguishes them from ferrofluids, from the jamming of magnetic nanoparticles assembled at the interface between two distinct liquids to minimize surface tension. This perspective provides an overview of recent progress and discusses future directions, challenges and potential applications of jamming magnetic nanoparticles with regard to 3D nano-magnetism. We address the formation and characterization of curved magnetic geometries, and spin frustration between dipole-coupled nanostructures, and advance our understanding of …

Skyrmion Fluctuations At A First-Order Phase Transition Boundary, V. Esposito, X. Y. Zheng, M. H. Seaberg, S. A. Montoya, B. Holladay, A. H. Reid, R. Streubel, J. C.T. Lee, L. Shen, J. D. Koralek, G. Coslovich, P. Walter, S. Zohar, V. Thampy, M. F. Lin, P. Hart, K. Nakahara, P. Fischer, W. Colocho, A. Lutman, F. J. Decker, S. K. Sinha, E. E. Fullerton, S. D. Kevan, S. Roy, M. Dunne, J. J. Turner

Robert Streubel Papers

Magnetic skyrmions are topologically protected spin textures with promising prospects for applications in data storage. They can form a lattice state due to competing magnetic interactions and are commonly found in a small region of the temperature - magnetic field phase diagram. Recent work has demonstrated that these magnetic quasi-particles fluctuate at the μeV energy scale. Here, we use a coherent x-ray correlation method at an x-ray free-electron laser to investigate these fluctuations in a magnetic phase coexistence region near a first-order transition boundary where fluctuations are not expected to play a major role. Surprisingly, we find that the relaxation …

Symmetry And Interface Considerations For Interactions On Mos2, Prescott E. Evans

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

The critical role of symmetry, in adsorbate-MoS₂ interactions, has been demonstrated through a variety of electronic structure, topology, and catalytic studies of MoS₂ and MoS₂ composites.A combination of density functional theory and experiment exhibiting diiodobenzene isomer dependent adsorption rates highlight frontier orbital symmetry as key to adsorption on MoS₂. It is clear that the geometry and symmetry of MoS₂ influences the creation and stability of surface defects, that in turn affect catalytic activity and a myriad of other applications. We have shown that surface reactions such the methanol to methoxy reaction can create defects …

Questaal: A Package Of Electronic Structure Methods Based On The Linear Muffin-Tin Orbital Technique, Dimitar Pashov, Swagata Acharya, Walter R.L. Lambrecht, Jerome Jackson, Kirill Belashchenko, Athanasios Chantis, Francois Jamet, Mark Van Schilfgaarde

Kirill Belashchenko Publications

This paper summarises the theory and functionality behind Questaal, an open-source suite of codes for calculating the electronic structure and related properties of materials from first principles. The formalism of the linearised muffin-tin orbital (LMTO) method is revisited in detail and developed further by the introduction of short-ranged tight-binding basis functions for full-potential calculations. The LMTO method is presented in both Green's function and wave function formulations for bulk and layered systems. The suite's full-potential LMTO code uses a sophisticated basis and augmentation method that allows an efficient and precise solution to the band problem at different levels of theory, …

The Emergence Of The Local Moment Molecular Spin Transistor, Guanhua Hao, Ruihua Cheng, Peter Dowben

Peter Dowben Publications

Local moment molecular systems have now been used as the conduction channel in gated spintronics devices, and some of these three terminal devices might even be considered molecular spin transistors. In these systems, the gate voltage can be used to tune the molecular level alignment, while applied magnetic fields have an influence on the spin state, altering the magnetic properties, and providing insights to the magnetic anisotropy. More recently, the use of molecular spin crossover complexes, as the conduction channel, has led to devices that are both nonvolatile and have functionality at higher temperatures. Indeed, some devices have now been …

Probing Ferroelectricity By X-Ray Absorption Spectroscopy In Molecular Crystals, Fujie Tang, Xuanyuan Jiang, Hsin Yu Ko, Jianhang Xu, Mehmet Topsakal, Guanhua Hao, Alpha T. N'Diaye, Peter Dowben, Deyu Lu, Xiaoshan Xu, Xifan Wu

Peter Dowben Publications

We carry out X-ray absorption spectroscopy experiment at the oxygen K edge in croconic acid (C₅H₂O₅) crystal as a prototype of ferroelectric organic molecular solid, whose electric polarization is generated by proton transfer. The experimental spectrum is well reproduced by the electron-hole excitation theory simulations from configuration generated by ab initio molecular dynamics simulation. When inversion symmetry is broken in the ferroelectric state, the hydrogen bonding environment on the two bonded molecules become inequivalent. Such a difference is sensitively probed by the bound excitation in the pre-edge, which is strongly localized on the excited …

Infrared-Active Phonon Modes In Single-Crystal Thorium Dioxide And Uranium Dioxide, Sean Knight, Rafal Korlacki, Christina Dugan, James C. Petrosky, Alyssa Lynn Mock, Peter A. Dowben, J. Matthew Mann, Martin M. Kimani, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

The infrared-active phonon modes, in single-crystal samples of thorium dioxide (ThO₂) and uranium dioxide (UO₂), were investigated using spectroscopic ellipsometry and compared with density functional theory. Both ThO₂ and UO₂ are found to have one infrared-active phonon mode pair [consisting of one transverse optic (TO) and one associated longitudinal optic (LO) mode], which is responsible for the dominant features in the ellipsometric data. At room temperature, our results for the mode pair’s resonant frequencies and broadening parameters are comparable with previous reflectance spectroscopy characterizations and density functional theory predictions. For ThO₂, our …

Effects Of Intrinsic Defects And Alloying With Fe On The Half-Metallicity Of Co2Mnsi, G. G. Baez Flores, Ivan A. Zhuravlev, Kirill Belashchenko

Kirill Belashchenko Publications

The electronic structure and half-metallic gap of Co2MnSi in the presence of crystallographic defects, partial Fe substitution for Mn, and thermal spin fluctuations are studied using the coherent potential approximation and the disordered local moment method. In the presence of 5% Co or Mn vacancies the Fermi level shifts down to the minority-spin valence-band maximum. In contrast to NiMnSb, both types of Mn antisite defects in Co2MnSi are strongly exchange coupled to the host magnetization, and thermal spin fluctuations do not strongly affect the half-metallic gap. Partial substitution of Mn by Fe results in considerable changes in the Bloch spectral …

Itinerant Ferromagnetism And Intrinsic Anomalous Hall Effect In Amorphous Iron-Germanium, D. S. Bouma, Z. Chen, B. Zhang, F. Bruni, M. E. Flatté, A. Ceballos, R. Streubel, L. W. Wang, R. Q. Wu, F. Hellman

Robert Streubel Papers

The amorphous iron-germanium system (a-Fe_xGe_1-x) lacks long-range structural order and hence lacks a meaningful Brillouin zone. The magnetization of a-Fe_xGe_1-x is well explained by the Stoner model for Fe concentrations x above the onset of magnetic order around x=0.4, indicating that the local order of the amorphous structure preserves the spin-split density of states of the Fe-3d states sufficiently to polarize the electronic structure despite k being a bad quantum number. Measurements reveal an enhanced anomalous Hall resistivity ρ_xy^AH relative to crystalline FeGe; this ρ_xy^AH is compared to density-functional …

Diffusion Doping Of Cobalt In Rod-Shape Anatase Tio2 Nanocrystals Leads To Antiferromagnetism†, Shahzahan Mia, Shelton J.P. Varapragasam, Aravind Baride, Choumini Balasanthiran, Balamurugan Balasubramanian, Robert M. Rioux, James D. Hoefelmeyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Cobalt(II) ions were adsorbed to the surface of rod-shape anatase TiO2 nanocrystals and subsequently heated to promote ion diffusion into the nanocrystal. After removal of any remaining surface bound cobalt, a sample consisting of strictly cobalt-doped TiO2 was obtained and characterized with powder Xray diffraction, transmission electron microscopy, UV-visible spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy, SQUID magnetometry, and inductively-coupled plasma atomic emission spectroscopy. The nanocrystal morphology was unchanged in the process and no new crystal phases were detected. The concentration of cobalt in the doped samples linearly correlates with the initial loading of cobalt(II) ions on the nanocrystal surface. Thin …

Detection Of Decoupled Surface And Bulk States In Epitaxial Orthorhombic Sriro3 Thin Films, Prescott E. Evans, Takashi Komesu, Le Zhang, Ding-Fu Shao, Andrew J. Yost, Shiv Kumar, Eike F. Schwier, Kenya Shimada, Evgeny Y. Tsymbal, Xia Hong, P. A. Dowben

Peter Dowben Publications

We report the experimental evidence of evolving lattice distortion in high quality epitaxial orthorhombic SrIrO3(001) thin films fully strained on (001) SrTiO3 substrates. Angle-resolved X-ray photoemission spectroscopy studies show that the surface layer of 5 nm SrIrO3 films is Sr–O terminated, and subsequent layers recover the semimetallic state, with the band structure consistent with an orthorhombic SrIrO3(001) having the lattice constant of the substrate. While there is no band folding in the experimental band structure, additional super-periodicity is evident in low energy electron diffraction measurements, suggesting the emergence of a transition layer with crystal symmetry evolving from the SrTiO3 substrate …

Manipulation Of The Molecular Spin Crossover Transition Of Fe(H2b(Pz)2)2(Bipy) By Addition Of Polar Molecules, Paulo S. Costa, Guanhua Hao, Alpha T. N'Diaye, Lucie Routaboul, Pierre Braunstein, Xin Zhang, Jian Zhang, Thilini K. Ekanayaka, Qin Yin Shi, V. L. Schlegel, Bernard Doudin, Axel Enders, Peter Dowben

Peter Dowben Publications

The addition of various dipolar molecules is shown to affect the temperature dependence of the spin state occupancy of the much studied spin crossover Fe(II) complex, [Fe{H2B(pz)2}2(bipy)] (pz = pyrazol-1-yl, bipy = 2,2′-bipyridine). Specifically, the addition of benzimidazole results in a re-entrant spin crossover transition, i.e. the spin state starts in the mostly low spin state, then high spin state occupancy increases, and finally the high spin state occupancy decreases with increasing temperature. This behavior contrasts with that observed when the highly polar p -benzoquinonemonoimine zwitterion C6H2(..NH2)2(..O)2 was mixed with [Fe{H2B(pz)2}2(bipy)], which resulted in locking [Fe{H2B(pz)2}2(bipy)] largely into a low …

Launching A New Dimension With 3d Magnetic Nanostructures, Peter Fischer, Dédalo Sanz-Hernández, Robert Streubel, Amalio Fernández-Pacheco

Robert Streubel Papers

The scientific and technological exploration of three-dimensional magnetic nanostructures is an emerging research field that opens the path to exciting novel physical phenomena, originating from the increased complexity in spin textures, topology, and frustration in three dimensions. One can also anticipate a tremendous potential for novel applications with those systems in a magnetic sensor and information processing technologies in terms of improved energy efficiency, processing speed, functionalities, and miniaturization of future spintronic devices. These three-dimensional structures are distinct from traditional bulk systems as they harness the scientific achievements of nanomagnetism, which aimed at lowering the dimensions down to the atomic …

Polar Coupling Enabled Nonlinear Optical Filtering At Mos2/Ferroelectric Heterointerfaces, D. W. Li, Xi Huang, Zhiyong Xiao, Hanying Chen, Le Zhang, Yifei Hao, Jingfeng Song, Ding-Fu Shao, Evgeny Y. Tsymbal, Yongfeng Lu, Xia Hong

Evgeny Tsymbal Publications

Complex oxide heterointerfaces and van der Waals heterostructures present two versatile but intrinsically different platforms for exploring emergent quantum phenomena and designing new functionalities. The rich opportunity offered by the synergy between these two classes of materials, however, is yet to be charted. Here, we report an unconventional nonlinear optical filtering effect resulting from the interfacial polar alignment between monolayer MoS₂ and a neighboring ferroelectric oxide thin film. The second harmonic generation response at the heterointerface is either substantially enhanced or almost entirely quenched by an underlying ferroelectric domain wall depending on its chirality, and can be further tailored …

Detection Of Decoupled Surface And Bulk States In Epitaxial Orthorhombic Sriro3 Thin Films, Prescott E. Evans, Takashi Komesu, Le Zhange, Ding-Fu Shao, Andrew J. Yost, Shiv Kumar, Elke F. Schwier, Kenya Shimada, Evgeny Y. Tsymbal, Xia Hong, Peter A. Dowben

Evgeny Tsymbal Publications

We report the experimental evidence of evolving lattice distortion in high quality epitaxial orthorhombic SrIrO₃(001) thin films fully strained on (001) SrTiO₃ substrates. Angle-resolved X-ray photoemission spectroscopy studies show that the surface layer of 5 nm SrIrO₃ films is Sr–O terminated, and subsequent layers recover the semimetallic state, with the band structure consistent with an orthorhombic SrIrO₃(001) having the lattice constant of the substrate. While there is no band folding in the experimental band structure, additional super-periodicity is evident in low energy electron diffraction measurements, suggesting the emergence of a transition layer with crystal …

Colossal Flexoresistance In Dielectrics, Sung Min Park, Bo Wang, Tula R. Paudel, Se Young Park, Saikat Das, Jeong Rae Kim, Eun Kyo Ko, Han Gyeol Lee, Nahee Park, Lingling Tao, Dongseok Suh, Evgeny Y. Tsymbal, Long-Qing Chen, Tae Won Noh, Daesu Lee

Evgeny Tsymbal Publications

Dielectrics have long been considered as unsuitable for pure electrical switches; under weak electric fields, they show extremely low conductivity, whereas under strong fields, they suffer from irreversible damage. Here, we show that flexoelectricity enables damage-free exposure of dielectrics to strong electric fields, leading to reversible switching between electrical states —insulating and conducting. Applying strain gradients with an atomic force microscope tip polarizes an ultrathin film of an archetypal dielectric SrTiO₃ via flexoelectricity, which in turn generates non-destructive, strong electrostatic fields. When the applied strain gradient exceeds a certain value, SrTiO₃ suddenly becomes highly conductive, yielding at least …

Evaluating Thermoelectric Properties Of Batis3 By Density Functional Theory, Tula R. Paudel, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

BaTiS₃ is a semiconductor with a small bandgap of ∼0.5 eV and strong transport anisotropy caused primarily by structural anisotropy; it contains well-separated octahedral columns along the [0001] direction and low lattice thermal conductivity, appealing for thermoelectric applications. Here, we evaluate the prospect of BaTiS₃ as a thermoelectric material by using the linearized electron and phonon Boltzmann transport theory based on the firstprinciples density functional band structure calculations. We find sizable values of the key thermoelectric parameters, such as the maximum power factor PF = 928 μWK⁻² and the maximum figure of merit ZT = 0.48 for …

Epitaxial Antiperovskite/Perovskite Heterostructures For Materials Design, Camilo X. Quintela, Kyung Song, Ding-Fu Shao, Lin Xie, Tianxiang Nan, Tula R. Paudel, Neil Campbell, Xiaoqing Pan, Thomas Tybell, Mark S. Rzchowski, Evgeny Y. Tsymbal, Si-Young Choi, Chang-Beom Eom

Evgeny Tsymbal Publications

Engineered heterostructures formed by complex oxide materials are a rich source of emergent phenomena and technological applications. In the quest for new functionality, a vastly unexplored avenue is interfacing oxide perovskites with materials having dissimilar crystallochemical properties. Here, we propose a unique class of heterointerfaces based on nitride antiperovskite and oxide perovskite materials as a previously unidentified direction for materials design. We demonstrate the fabrication of atomically sharp interfaces between nitride antiperovskite Mn₃GaN and oxide perovskites (La_0.3Sr_0.7)(Al_0.65Ta_0.35)O₃ and SrTiO₃. Using atomic-resolution imaging/ spectroscopic techniques and first-principles calculations, …

Chiral Magnetism And High-Temperature Skyrmions In B20-Ordered Co-Si, Balamurugan Balasubramanian, Priyanka Manchanda, Rabindra Pahari, Zhen Chen, Wenyong Zhang, Shah R. Valloppilly, Xingzhong Li, Anandakumar Sarella, Lanping Yue, Ahsan Ullah, Pratibha Dev, David A. Muller, Ralph Skomski, George C. Hadjipanayis, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Magnets with chiral crystal structures and helical spin structures have recently attracted much attention as potential spin-electronics materials, but their relatively low magnetic-ordering temperatures are a disadvantage. While cobalt has long been recognized as an element that promotes high-temperature magnetic ordering, most Co-rich alloys are achiral and exhibit collinear rather than helimagnetic order. Crystallographically, the B20-ordered compound CoSi is an exception due to its chiral structure, but it does not exhibit any kind of magnetic order. Here, we use nonequilibrium processing to produce B20-ordered Co_1+xSi_1−x with a maximum Co solubility of x = 0.043. Above a critical …

Rod-Shape Theranostic Nanoparticles Facilitate Antiretroviral Drug Biodistribution And Activity In Human Immunodeficiency Virus Susceptible Cells And Tissues, Bhavesh D. Kevadiya, Brendan Ottemann, Insiya Z. Mukadam, Laura Castellanos, Kristen Sikora, James R. Hilaire, Jatin Machhi, Jonathan Herskovitz, Dhruvkumar Soni, Mahmudul Hasan, Wenting Zhang, Anandakumar Sarella, Jered Garrison, Joellyn Mcmillan, Benson Edagwa, R. Lee Mosley, Richard W. Vachet, Howard E. Gendelman

Nebraska Center for Materials and Nanoscience: Faculty Publications

Human immunodeficiency virus theranostics facilitates the development of long acting (LA) antiretroviral drugs (ARVs) by defining drug-particle cell depots. Optimal drug formulations are made possible based on precise particle composition, structure, shape and size. Through the creation of rod-shaped particles of defined sizes reflective of native LA drugs, theranostic probes can be deployed to measure particle-cell and tissue biodistribution, antiretroviral activities and drug retention.

Methods: Herein, we created multimodal rilpivirine (RPV) ¹⁷⁷lutetium labeled bismuth sulfide nanorods (¹⁷⁷LuBSNRs) then evaluated their structure, morphology, configuration, chemical composition, biological responses and adverse reactions. Particle biodistribution was analyzed by single …

Svat4: A Computer Program For Visualization And Analysis Of Crystal Structures, Xingzhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

SVAT4 is a computer program for interactive visualization of three-dimensional crystal structures, including chemical bonds and magnetic moments. A wide range of functions, e.g. revealing atomic layers and polyhedral clusters, are available for further structural analysis. Atomic sizes, colors, appearance, view directions and view modes (orthographic or perspective views) are adjustable. Customized work for the visualization and analysis can be saved and then reloaded. SVAT4 provides a template to simplify the process of preparation of a new data file. SVAT4 can generate high-quality images for publication and animations for presentations. The usability of SVAT4 is broadened by a software suite …

Intrinsic Spin Nernst Effect Of Magnons In A Noncollinear Antiferromagnet, Bo Li, Shane Sandhoefner, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We investigate the intrinsic magnon spin current in a noncollinear antiferromagnetic insulator. We introduce a definition of the magnon spin current in a noncollinear antiferromagnet and find that it is in general nonconserved, but for certain symmetries and spin polarizations the averaged effect of nonconserving terms can vanish. We formulate a general linear response theory for magnons in noncollinear antiferromagnets subject to a temperature gradient and analyze the effect of symmetries on the response tensor. We apply this theory to single-layer potassium iron jarosite KFe3(OH)6(SO4)2 and predict a measurable spin current response.

Controlling Spin Current Polarization Through Non-Collinear Antiferromagnetism, T. Nan, Camilo X. Quintela, J. Irwin, Gautam Gurung, D. F. Shao, J. Gibbons, Neil Campbell, K. Song, Si-Young Choi, L. Guo, R. D. Johnson, P. Manuel, R. V. Chopdekar, I. Hallsteinsen, Thomas Tybell, P. J. Ryan, J.-W. Kim, Y. Choi, P. G. Radaelli, D. C. Ralph, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom

Evgeny Tsymbal Publications

The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn₃GaN, in which the triangular spin structure creates a low magnetic symmetry while maintaining a …

Insulator-To-Conductor Transition Controlled By The Rashba-Zeeman Effect, Lingling Tao, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

The Rashba effect has recently attracted great attention owing to emerging physical properties associated with it. The interplay between the Rashba effect and the Zeeman effect, being produced by the exchange field, is expected to broaden the range of these properties and even result in novel phenomena. Here we predict an insulator-to-conductor transition driven by the Rashba–Zeeman effect. We first illustrate this effect using a general Hamiltonian model and show that the insulator-to-conductor transition can be triggered under certain Rashba and exchange-field strengths. Then, we exemplify this phenomenon by considering an Ag₂Te/Cr₂O₃ heterostructure, where the …

Nonlinear Anomalous Hall Effect For Néel Vector Detection, Ding-Fu Shao, Shu-Hui Zhang, Gautam Gurung, Wen Yang, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Antiferromagnetic (AFM) spintronics exploits the N´eel vector as a state variable for novel spintronic devices. Recent studies have shown that the fieldlike and antidamping spin-orbit torques (SOTs) can be used to switch the N´eel vector in antiferromagnets with proper symmetries. However, the precise detection of the N´eel vector remains a challenging problem. In this Letter, we predict that the nonlinear anomalous Hall effect (AHE) can be used to detect the N´eel vector in most compensated antiferromagnets supporting the antidamping SOT. We show that the magnetic crystal group symmetry of these antiferromagnets combined with spin-orbit coupling produce a sizable Berry curvature …

Interfacial Contributions To Spin-Orbit Torque And Magnetoresistance In Ferromagnet/Heavy-Metal Bilayers, Kirill Belashchenko, Alexey Kovalev, Mark Van Schilfgaarde

Department of Physics and Astronomy: Faculty Publications

The thickness dependence of spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers is studied using the first-principles nonequilibrium Green’s function formalism combined with the Anderson disorder model. A systematic expansion in orthogonal vector spherical harmonics is used for the angular dependence of the torque. The dampinglike torque in Co/Pt and Co/Au bilayers can be described as a sum of the spin-Hall contribution, which increases with thickness in agreement with the spin-diffusion model, and a comparable interfacial contribution. The magnetoconductance in the plane perpendicular to the current in Co/Pt bilayers is of the order of a conductance quantum per interfacial atom, exceeding …

Magnonic Analog Of The Edelstein Effect In Antiferromagnetic Insulators, Bo Li, Alexander Mook, Aldo Raeliarijaona, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We investigate the nonequilibrium spin polarization due to a temperature gradient in antiferromagnetic insulators, which is the magnonic analog of the inverse spin-galvanic effect of electrons. We derive a linear-response theory of a temperature-gradient-induced spin polarization for collinear and noncollinear antiferromagnets, which comprises both extrinsic and intrinsic contributions. We apply our theory to several noncentrosymmetric antiferromagnetic insulators, i.e., to a one-dimensional antiferromagnetic spin chain, a single layer of kagome noncollinear antiferromagnet,e.g.,KFe3(OH)6(SO4)2,and a noncollinear breathing pyrochlore antiferromagnet, e.g., LiGaCr4O8. The shapes of our numerically evaluated response tensors agree with those implied by the magnetic symmetry. Assuming a realistic temperature gradient of …

Magnon Landau Levels And Spin Responses In Antiferromagnets, Bo Li, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We study gauge fields produced by gradients of the Dzyaloshinskii-Moriya interaction and propose a model of an AFM topological insulator of magnons. In the long wavelength limit, the Landau levels induced by the inhomogeneous Dzyaloshinskii-Moriya interaction exhibit relativistic physics described by the Klein-Gordon equation. The spin Nernst response due to the formation of magnonic Landau levels is compared to similar topological responses in skyrmion and vortex-antivortex crystal phases of AFM insulators. Our studies show that AFM insulators exhibit rich physics associated with topological magnon excitations.

Ferroelectric Domain Wall Memristor, James P. V. Mcconville, Haidong Lu, Bo Wang, Yueze Tan, Charlotte Cochard, Michele Conroy, Kalani Moore, Alan Harvey, Ursel Bangert, Long-Qing Chen, Alexei Gruverman, J. M. Gregg

Alexei Gruverman Publications

A domain wall-enabled memristor is created, in thin film lithium niobate capacitors, which shows up to twelve orders of magnitude variation in resistance. Such dramatic changes are caused by the injection of strongly inclined conducting ferroelectric domain walls, which provide conduits for current flow between electrodes. Varying the magnitude of the applied electric-field pulse, used to induce switching, alters the extent to which polarization reversal occurs; this systematically changes the density of the injected conducting domain walls in the ferroelectric layer and hence the resistivity of the capacitor structure as a whole. Hundreds of distinct conductance states can be produced, …