Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session N28: 2D magnetism in van der Waals materialsInvited Live Streamed
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Sponsoring Units: GMAG DCMP DMP Chair: Inhee Lee; Ohio State University Simranjeet Singh, Carnegie Mellon Univ. Room: McCormick Place W-190A |
Wednesday, March 16, 2022 11:30AM - 12:06PM |
N28.00001: Raman spectroscopy of phonons and their coupling to excitons and layered magnetism in 2D magnet CrI3 Invited Speaker: Rui He Two-dimensional (2D) materials with intrinsic ferromagnetism have attracted massive interest because of their potential applications in data storage and spintronics devices. Atomic layers of chromium triiodide (CrI3) are one of such 2D ferromagnetic (FM) materials that have been demonstrated to realize long range FM order in its monolayer limit. In this talk I will show our Raman spectroscopy studies of electron-phonon coupling and coupling between an Eg phonon and layered magnetism in 2D CrI3. Our magneto-optical studies of twisted double bilayer CrI3 will also be discussed. Our results reveal the emergence of finite net magnetization that originates from spin frustrations introduced by moiré superstructures in twisted double bilayer CrI3. |
Wednesday, March 16, 2022 12:06PM - 12:42PM |
N28.00002: Identifying Fundamental Spin Interactions in CrI3, CrBr3, and CrCl3 through Ferromagnetic Resonance Invited Speaker: Inhee Lee Fundamental spin interactions in two-dimensional (2D) ferromagnets CrI3, CrBr3, and CrCl3 were determined through analysis of angle dependent ferromagnetic resonance (FMR). Van der Waals 2D ferromagnets have attracted much attention since the advent of atomic monolayer ferromagnets. However, little was known about the fundamental spin interactions underlying 2D ferromagnetism and the origin of their magnetic anisotropy. A new spin model constrained by crystal symmetries based on three main spin interactions, Heisenberg, Kitaev, and off-diagonal symmetric exchange interactions describes these data well. Their precise strengths are determined experimentally obtained from FMR and Curie temperature. One key finding is that the Kitaev interaction is much stronger than other interactions in CrI3. This surprising result is expected to provide important guidance for realizing novel 2D spin orders, such as magnetically frustrated quantum spin liquids. This Kitaev interaction opens a ~ 4 meV gap in the magnon band, which is corroborated by recent inelastic neutron scattering measurements. We extend our FMR studies to other chromium trihalides, such as CrBr3 and CrCl3, to gain a more general understanding of the spin exchange interactions associated with spin-orbit coupling. |
Wednesday, March 16, 2022 12:42PM - 1:18PM |
N28.00003: Quantum sensing and imaging of two-dimensional magnets Invited Speaker: David A Broadway The recent discovery of long-range magnetic order in atomically thin ``van der Waals’’ (vdW) crystals [1] has attracted significant attention due to their fundamental and technological interest, including predictions of exotic magnetic phases and unique opportunities to control magnetism at the atomic scale. Yet, nanoscale imaging tools to address spin textures in these magnets have been missing until recently, despite the key role they play for future developments in the field. |
Wednesday, March 16, 2022 1:18PM - 1:54PM |
N28.00004: Quantum materials with low crystalline symmetry for field-free magnetization manipulation Invited Speaker: Simranjeet Singh Spin-orbit torque (SOT) driven control of the magnetization state of a ferromagnet is key to next generation spintronic applications including non-volatile, ultrafast, and energy efficient data storage devices. But field-free deterministic SOT switching of perpendicular magnetization remains a challenge because electric current induced spin polarization in conventional spin source materials, such as heavy metals and topological insulators, is constrained to the film plane due to the system's symmetry. The exploitation of low-crystal symmetries in emergent quantum materials offers a unique approach to achieve SOTs with unconventional forms. In this context, Weyl semimetals (WSMs) with low-crystal symmetries provide a distinct possibility to obtain highly efficient and unconventional charge to spin conversion. We will present our results showing the experimental realization of field-free deterministic switching of a perpendicularly polarized vdW ferromagnet employing WTe2, which is a type-II WSM candidate with low-symmetry crystal structure. |
Wednesday, March 16, 2022 1:54PM - 2:30PM |
N28.00005: Magnetic Anisotropy in higher-spin with heavy ligand in honeycomb Mott Insulators: Application to CrI3 Invited Speaker: Hae-Young Kee Fascinating features of van der Waals magnetic materials have attracted much attention from theoretical and experimental researchers. Recently spin models for two-dimensional Mott insulators beyond the standard Heisenberg interaction have been developed. In particular, the bond-dependent spin ½ Kitaev model on honeycomb lattice is a rare example of exactly solvable model, which exhibits non-Abelian anyons under a magnetic field. Several candidate materials have been proposed and the Kitaev model with higher spins has been also studied. I will present a microscopic route to achieve higher spin Kitaev models in solid state materials [1], and its application to S=3/2 CrI3 [2]. I will also discuss experimental strategies to extract the Kitaev and other bond-dependent Gamma interactions using the symmetry of a generic Hamiltonian. |
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