Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session W57: Topological, magnetoresistance and multiferroicityFocus
|
Hide Abstracts |
Sponsoring Units: GMAG Chair: Qiang Zhang, Oak Ridge National Lab Room: Room 303 |
Thursday, March 9, 2023 3:00PM - 3:36PM |
W57.00001: Eu2Cd2As2 as a candidate Weyl Hydrogen Atom Invited Speaker: Keith M Taddei It is an unexpected turn in condensed matter physics that we find ourselves hunting for solutions to the relativistic wave equation. Exotic particles such as the massless chiral Weyl Fermion which have been extensively and unsuccessfully sought in high energy physics are finding new life as quasiparticle excitations in carefully constructed solid state electronic band structures. In condensed matter, such particles arise from non-trivial topological invariants and thus, not only do they yield exotic transport properties, but the associated states are also topologically protected and therefore potentially useful. Yet finding them in ideal configurations has proven quite challenging. |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W57.00002: The effect of nuclear spins on the spin transport at the surface of three-dimensional topological insulator Inanc Adagideli, Alexander Brinkman, A. Mert Bozkurt Topological surface states of a three-dimensional topological insulator offer a promising platform for spintronics applications due to perfect spin-momentum locking feature of its band structure. We investigate the effect of nuclear spins interacting with the electrons at the surface of a three-dimensional topological insulator. The interaction between surface electrons and nuclear spins that are naturally present at the surface has only been considered as a source of backscattering. In this paper, we find that the angular momentum of the electrons can be transferred to the nuclear spin subsystem, leading to dynamical nuclear spin polarization. We also show that the reverse process is also possible, namely a finite nuclear spin polarization can induce a spin current at the surface of a three-dimensional topological insulator. We demonstrate this by deriving the quantum kinetic equation using nonequilibrium Green's function formalism and obtain the diffusion equation for the electrons at the surface of a three-dimensional topological insulator. We show that in the diffusive limit, dynamical polarization of the nuclear spin subsystem is achievable and the degree of polarization depends on the ratio of mean free path and system size.
|
Thursday, March 9, 2023 3:48PM - 4:00PM |
W57.00003: Tunable Optical Bandgap in GdN Ultrathin Films for Spin Filtering Gilvania L Da Silva Vilela, Geetha Berera, Gregory Stepehn, Xavier Gratens, Pavel Usachev, Don Heiman, Andre Henriques, Jagadeesh S Moodera Spintronic devices based on rare-earth nitrides (RENs) are of great interest since they present semiconducting and ferromagnetic properties suitable for exploiting carriers' spin in fundamental and applied research. GdN has been widely studied due to its high magnetic moment and spin-splitting bandgap attributed to the bandgap shrinking and the different energies for the minority and majority bands. Because of its high oxophilicity, the growth of stoichiometric GdN thin ?lms is very challenging and requires rigorous control of impurities. Besides that, to combine GdN films with novel materials for investigating interface and spin phenomena, flat surfaces with a high degree of crystallinity, well-defined bandgap, and critical temperature and magnetization saturation compatible with the bulk values are crucial. The crystal, optical and magnetic properties of GdN films depend on strain, nitrogen vacancies, and the amount of oxygen impurities which depend on the growth process and substrate choices. In this work, we investigate the optical and magnetic properties of reactively sputtered AlN(10 nm)/GdN(t)/AlN(10 nm) on sapphire substrates with different thicknesses grown under different nitrogen’s partial pressure and temperature. We observed an increase of the GdN film bandgaps under a transition from the paramagnetic to the ferromagnetic state for a thickness t ranging from 4 nm to 350 nm. Next, we have been working on observing and controlling the spin-split bandgap of these films. |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W57.00004: First Principles Study of the Electronic Structure of the Ni2MnIn/InAs and Ti2MnIn/InSb Interfaces Derek Dardzinski We present a first-principles study of the electronic and magnetic properties of epitaxial interfaces between the Heusler compounds Ti2MnIn and Ni2MnIn and the III-V semiconductors, InSb and InAs, respectively. We use density functional theory (DFT) with a machine-learned Hubbard U correction determined by Bayesian optimization. We evaluate these interfaces for prospective applications in Majorana-based quantum computing and spintronics. In both interfaces, states from the Heusler penetrate into the gap of the semiconductor, decaying within a few atomic layers. The magnetic interactions at the interface are weak and local in space and energy. Magnetic moments of less than 0.1 μB are induced in the two atomic layers closest to the interface. The induced spin polarization around the Fermi level of the semiconductor also decays within a few atomic layers. The decisive factor for the induced spin polarization around the Fermi level of the semiconductor is the spin polarization around the Fermi level in the Heusler, rather than the overall magnetic moment. As a result, the ferrimagnetic narrow-gap semiconductor Ti2MnIn induces a more significant spin polarization in the InSb than the ferromagnetic metal Ni2MnIn induces in the InAs. This is explained by the position of the transition metal d states in the Heusler with respect to the Fermi level. Based on our results, these interfaces are unlikely to be useful for Majorana devices but could be of interest for spintronics. |
Thursday, March 9, 2023 4:12PM - 4:24PM |
W57.00005: Discovery of a new polar magnetic semiconductor MnCuSiTe3 with spin-induced electric polarization CHANDAN DE, Suguru Yoshida, Weiwei Xie, Qiang Zhang, Lujin Min, Zhiqiang Mao Layered polar magnetic semiconductors are currently of emerging interest for their nonlinear and various functional properties. To date, only few layered ferroelectrics have been found while plenty of layered materials show long-range magnetic ordering. In this talk, we report a new layered quaternary chalcogenide MnCuSiTe3 which shows a polar structure at room temperature and multiple magnetic transitions at low temperature. We demonstrated its polar nature with piezoelectric response along with a large Second Harmonic Generation signal at room temperature. Moreover, we also found a remarkable electric polarization below the long-range antiferromagnetic transition at TN=35K. Further, we also probed pyroelectric current below TN. These results suggest MnCuSiTe3 may exhibit a multiferroic state below TN. |
Thursday, March 9, 2023 4:24PM - 4:36PM |
W57.00006: Spectroscopic evidence for spin splitting in a collinear antiferromagnet Suyoung Lee, Changyoung Kim, Sangjae Lee, Donghan Kim The Anomalous Hall effect (AHE) has been understood in close relation to nontrivial band topology. Recently, it has been proposed that AHE can arise in compensated collinear magnets with opposite-spin sublattices connected by rotational symmetry. This distinct magnetic phase, so-called 'altermagnetism', is characterized by time-reversal symmetry (TRS) broken electronic structure with non-relativistic spin-momentum locking. We performed angle-resolved photoemission spectroscopy (ARPES) on semiconducting MnTe, an altermagnetic candidate. Spin-split electronic structure with a large splitting of ~1 eV is clearly resolved. The compensated magnetic semiconductor with TRS-broken electonic structure provides a new platform for novel topological spintronics. |
Thursday, March 9, 2023 4:36PM - 4:48PM |
W57.00007: Anisotropic magnetoresistance and anomalous Nernst effect in antiferromagnetic MnTe thin films Weilun Tan, Haoyu Liu, Michael Chilcote, Alessandro Mazza, Matthew Brahlek, Jing Shi The NiAs-type MnTe, an antiferromagnetic semiconductor, is theoretically predicted to exhibit exotic magneto-transport properties. For spintronic applications, the easy-plane magnetic anisotropy offers a unique advantage of having three possible Neel vector orientations for multi-state memory. However, the electrical detection and manipulation of the antiferromagnetic order parameter have not been explored. Here, we report a magneto-transport study carried out in MnTe thin films which are epitaxially grown on GaP substrates using molecular beam epitaxy. The Hall bar devices are fabricated on a 75 nm thick MnTe film by photolithography and Ar plasma dry etching. The four-terminal DC resistance vs. temperature curve shows a well-defined peak at 290 K, indicating the Neel temperature of the MnTe film. By performing the longitudinal resistance Rxx with a rotating in-plane magnetic field of fixed magnitude, we obtain Rxx oscillations as a function of the azimuthal angle. Even with a current density as small as ~2×105 A/m2, we observe a transition of the oscillation period from π to 2π as the field strength exceeds ~ 5 T. At low fields, the π-oscillation is characteristic of the anisotropic magnetoresistance due to the canted magnetic moment along the magnetic field direction. At high fields, the 2π oscillation indicates the anomalous Nernst effect under a small vertical temperature gradient produced by the Joule heating. In the intermediate field range, the Rxx displays a complex pattern, which is attributed to the role of in-plane anisotropy. Discussions about the underlying physical mechanism of the observed phenomena will be presented. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W57.00008: Magnetic excitations in noncolinear antiferromagnet MnTe2 Yufei Li, Alex D Giovannone, Thuc T Mai, Archibald . Williams, Joshua E Goldberger, Angela R Hight Walker, Rolando Valdes Aguilar A classification of topological magnon has been proposed (arXiv:2206.06248). One candidate that is predicted to have a triply degenerate magnon at zone center is MnTe2. It undergoes a second-order antiferromagnetic transition at around 87K. It was proposed that MnTe2 has a noncolinear magnetic ground state. (doi:10.1103/PhysRevB.56.14013) To study the magnetic interaction in MnTe2, we used time-domain Terahertz and Raman spectroscopies to measure excitations at different temperatures and in magnetic fields. An excitation at around 0.6 THz (2.5 meV) shows up below the transition temperature. We also show the field dependence of the excitations. The results help to understand the magnetic interaction between the Mn2+ ions. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W57.00009: Lattice-control of the chiral-orbital-current-driven colossal magnetoresistance in Mn3Si2Te6* Yifei Ni, Hengdi Zhao, Yu Zhang, Gang Cao Mn3Si2Te6 is a ferrimagnetic insulator which features a seven-order-of-magnitude colossal magnetoresistance (CMR) that happens only when the magnetic polarization is absent [1,2]. Our recent studies uncover that this exotic CMR is driven by chiral orbital currents (COC) flowing along the edges of MnTe6 octahedra [3]. The COC state is shown to be strongly coupled to the crystal structure and the Mn magnetic moments. Here we report results of our studies on lattice control via both chemical (doping) and hydrostatic pressure of the COC state in Mn3Si2Te6. The studies reveal a large magnetoelastic coupling, as such expanding the unit cell enhances the COC-driven CMR and shrinking the unit cell does otherwise. The results are presented with comparison drawn with other related materials [4]. |
Thursday, March 9, 2023 5:12PM - 5:24PM |
W57.00010: Nature of the ferromagnet-paramagnet transition in the hole-doped Mott insulator Y1-xCaxTiO3 Sajna Hameed, Issam Khayr, Joseph Joe, Yipeng Cai, Guoqiang Zhao, Qi Sheng, Kohtaro Yamakawa, Jiawei Zang, Changqing Jin, Lichen Fu, Yilin Gu, Fanlong Ning, Songxue Chi, Peter M Gehring, Travis J Williams, Zhijun Xu, Masaaki Matsuda, Kenji M Kojima, Yasutomo J Uemura, Martin Greven The perovskite titanate class of materials encompasses a wide variety of phenomena, including magnetic phase transitions, insulator-metal transitions, and superconductivity. In this talk, I will present our findings from neutron scattering, muon spin rotation and magnetic susceptibility measurements of the magnetically-ordered ground states and spin dynamics of the hole-doped Mott insulator Y1-xCaxTiO3. This system is known to exhibit an intriguing transition from ferromagnetic to paramagnetic state at x ~ 0.2 prior to undergoing an insulator-metal transition at x ~ 0.35 [1,2]. We find that the ferromagnetic phase extends into significantly higher hole-doping levels than previously reported and determine a first-order nature for the doping-induced ferromagnet-paramagnetic transition. |
Thursday, March 9, 2023 5:24PM - 5:36PM |
W57.00011: Antiferromagnetic insulating state in layered nickelates at half filling Myung-Chul Jung, Harrison LaBollita, Victor Pardo, Antia S Botana We provide a set of computational experiments based on ab initio calculations to elucidate whether a cuprate-like antiferromagnetic insulating state can be present in the phase diagram of the low-valence layered nickelate family (Rn+1NinO2n+2, R= rare-earth, n = 1−∞) in proximity to half-filling. It is well established that at d9 filling the infinite-layer (n = ∞) nickelate is metallic, in contrast to cuprates wherein an antiferromagnetic insulator is expected. We show that for the Ruddlesden-Popper (RP) reduced phases of the series (finite n) an antiferromagnetic insulating ground state can naturally be obtained instead at d9 filling, due to the spacer RO2 fluorite slabs present in their structure that block the c-axis dispersion. In the n = ∞ nickelate, the same type of solution can be derived if the off-plane R-Ni coupling is suppressed. We show how this can be achieved if a structural element that cuts off the c-axis dispersion is introduced (i.e. vacuum in a monolayer of RNiO2, or a blocking layer in multilayers formed by (RNiO2)1/(RNaO2)1). |
Thursday, March 9, 2023 5:36PM - 5:48PM |
W57.00012: Nonlinear field theory of a 3-sublattice hexagonal antiferromagnet Bastian F Pradenas, Oleg Tchernyshyov We derive the nonlinear field theory of a 3-sublattice hexagonal antiferromagnet. The order parameter can be parametrized as a rigid body made by the three vectors of sublattice magnetizations oriented at 120º to one another. Like in the linear spin-wave theory developed by us previously [1], the exchange energy density has three coupling constants reminiscent of the Lame parameters describing the elasticity of a hexagonal solid. Our theory generalizes the older work of Dombre and Read [2] for a triangular lattice, which turns out to be a special case with higher spatial symmetry. We show that a vortex in a 3-sublattice antiferromagnet with easy-plane anisotropy generally has an elliptical core, with the ellipticity determined by the ratio of Lame parameters. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700