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 M58: GMAG: Light Matter InteractionFocus
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Sponsoring Units: GMAG Chair: Zachary Morgan, Oak Ridge National Lab Room: Room 302 |
Wednesday, March 8, 2023 8:00AM - 8:36AM |
M58.00001: Suppressing spectral diffusion of phosphorus donor electron spins in natural silicon using optical excitation Invited Speaker: Chandrasekhar Ramanathan Donor and defect electronic spins in solids are promising platforms for quantum technologies. Understanding how these potential electron spin qubit candidates decohere under different experimental conditions is key to enabling improved performance. The donor electron spins in phosphorus-doped silicon (Si:P) have some of the longest coherence times observed in solid-state spin systems. Natural silicon consists of 3 isotopes - 28Si, 29Si and 30Si. While the 4.7% abundant 29Si is a spin-1/2 nucleus, 28Si and 30Si are spin-0 nuclei. Magnetic dipolar interactions between the 29Si spins induce a fluctuating nuclear magnetic field at the site of the donor electron spin resulting in a decay of the electron spin coherence. This spectral diffusion due to the 29Si spins is the dominant source of spin echo decay in lightly-doped natural Si:P samples at liquid helium temperatures in low magnetic fields (< 0.5 T). The elimination of the spin-1/2 29Si nuclei was seen to dramatically suppress spectral diffusion in low-field experiments on Si:P. |
Wednesday, March 8, 2023 8:36AM - 9:12AM |
M58.00002: Spin-Valley pumping and long electron spin transport in a transition metal dichalcogenide monolayer Invited Speaker: Cedric ROBERT Monolayers of transition metal dichalcogenides (TMD) are ideal semiconductor materials to control both spin and valley degrees of freedom either electrically or optically. Nevertheless, optical excitation mostly generates excitons species with inherently short lifetime and spin/valley relaxation time. In this presentation we will show that we can strongly polarize (up to 75%) the resident electrons in n-doped WSe2 and WS2 monolayers by using a circularly polarized continuous wave laser [1]. Then, using a spatially-resolved optical pump-probe experiment, we measure the lateral transport of spin/valley polarized electrons over very long distances (tens of micrometers) [2]. These results highlight the key role played by the spin-valley locking effect in TMD monolayers on the pumping efficiency and the polarized electron transport. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M58.00003: Terahertz Spin Resonance of Proximitized Dirac Electrons Konstantin Denisov, Igor V Rozhansky, Sergio O Valenzuela, Igor Zutic We investigate spin-light coupling phenomena in van der Waals heterostructures consisting of two-dimensional (2D) Dirac crystals proximitized by a magnetic layer. A strong magnetic proximity effect results in the modification of the 2D electron spectrum with the appearance of different spin-splitting terms and electron’s equilibrium spin polarization [1,2]. Motivated by these factors we have explored the resonant spin generation of proximitized Dirac electrons by THz ac-electric field and have revealed the existence of a new scenario for the electric dipole spin resonance (EDSR). We focus on the resonant spin dynamics of electrons in a single layer of magnetically proximitized graphene, and discuss emerging EDSR features absent in systems with a parabolic spectrum [3]. Our results demonstrate the enhancement of EDSR in a graphene and reveal an anomalous polarization structure of the absorption coefficient. The developed theory allowed us to propose a THz detector, in which the photogenerated nonequilibrium spin polarization in graphene can be read due to spin-charge tunneling conversion at the ferromagnet/graphene interface. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M58.00004: Tunable interactions between excitons and hybridized magnons in a layered semiconductor Geoffrey M Diederich The interaction between distinct excitations in solids is of both fundamental interest and technological importance. One such interaction is the coupling between an exciton, a Coulomb bound electron-hole pair, and a magnon, a collective spin excitation. The recent emergence of van der Waals magnetic semiconductors provides a platform for exploring these exciton-magnon interactions and their fundamental properties, such as strong correlation, as well as their photo-spintronic and quantum transduction applications. In this talk, I will demonstrate precise control of coherent exciton-magnon interactions in the layered magnetic semiconductor CrSBr. I will show how varying the direction of an applied magnetic field relative to the crystal axes breaks the rotational symmetry of the magnetic system. Thereby, one can tune not only the exciton coupling to the bright magnon, but also to an optically dark mode via magnon-magnon hybridization. Further, I will show how we modulated the exciton-magnon coupling and the associated magnon dispersion curves through the application of uniaxial strain. At the critical strain, a dispersionless dark magnon band emerges. The results I will present demonstrate unprecedented control of the opto-mechanical-magnonic coupling, and a step towards the predictable and controllable implementation of hybrid quantum magnonics. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M58.00005: Magnetically correlated defects in a quasi-1D electronic van der Waals magnetic semiconductor Julian Klein, Zhigang Song, Benjamin Pingault, Florian Dirnberger, Hang Chi, Jonathan Curtis, Rami Dana, Rezlind Bushati, Jiamin Quan, Lukas Dekanovsky, Zdenek Sofer, Andrea Alu, Vinod M Menon, Jagadeesh S Moodera, Marko Lon?ar, Prineha Narang, Frances M Ross Defects in two-dimensional magnets are interesting objects to study with prospects for engineering magnetic properties at the atomic scale. The air-stable magnetic semiconductor CrSBr exhibits excellent optical properties providing opportunities to study defect physics in a magnetic environment. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M58.00006: Developing III-V spin optoelectronic devices operating at zero magnetic field Yuan Lu, Pierre Renucci, Henri Jaffrès, Jean-Marie George, Xavier Marie Spin optoelectronic devices (spin light-emitting diode, spin laser and spin photodiode), which can convert the carrier spin polarization with the photon circular polarization, have gained intensive interest in the last decade. The potential applications of spin optoelectronic device can be used for optical communication, 3D display, biomedical analyses, etc. However, the obstacles for developing these applications are relied on the room temperature operation and without applying the magnetic field. According to the optical selection rule, for surface emitting and detecting geometry, the conventional spin injector with in-plane magnetization requires a strong external magnetic field in the range of a few Tesla, which is impossible for the practical application. Since 2014, we have developed the spin injector with perpendicular magnetic anisotropy (PMA) consisting of an ultrathin CoFeB (1.2 nm)/MgO (2.5 nm) on GaAs based quantum well (QW) [1] and quantum dot (QD) LED [2]. In this talk, I will give a presentation on our progress on developing PMA spin injector with better thermal stability [3], the evidence of polarization of nuclei spin by electron spin [2], the understanding of spin relaxation mechanism in spin LED [4] and the developing of spin photodiode with PMA spin detector [5]. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M58.00007: Spintronic Terahertz Emission in Ultrawide Bandgap Semiconductor/Ferromagnet Heterostructures Aeron McConnell Recent successful integration of semiconductors into spintronic THz emitters has demonstrated a new pathway of control over terahertz (THz) radiation through ultrafast demagnetization dynamics. Here, the spintronic THz emission from different ultrawide bandgap (UWBG) semiconductors interfaced with ferromagnets is studied. The authors show that the Schottky barrier in the UWBG semiconductor AlN acts as a spin filter that increases the polarization of the spin current injected from the ferromagnet. Furthermore, the authors show that the two-dimensional electron gas at the interface between Al0.25Ga0.75N and GaN enhances the magnitude of the emitted radiation due to the high spin-to-charge conversion efficiency induced by the Rashba effect that results in a hallmark asymmetry in emission amplitude. The results provide a framework for future engineering of semiconducting/ferromagnet heterostructures for ultrafast communications technologies beyond 5G. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M58.00008: The dynamics of circular polarization in spin-lasers. Krish Patel, Igor Zutic, Gaofeng Xu Through angular momentum conservation, injecting spin-polarized carriers in semiconductor lasers offers control of the helicity of emitted light [1,2]. This improves the operation of lasers, beyond what is possible with injecting unpolarized cariers [1] and offers paths for room-temperature spintronic applications, beyond magnetoresistance [2]. While dynamical operation of spin-lasers and their ultrafast switching [1] is crucial for possible applications, many operation regimes and effects remain unexplored [2,3]. In particular, the role of modulating carrier injection on the circular polarization of the emitted light in scaled-down spin-lasers is not understood. Even in the steady-state regime an enhanced contribution of spontaneous emission, usually assumed to be negligibly small, can strongly change their operation [4]. For the dynamical operation of spin-lasers we find various nonmontonic trends in materials parameters on the key properties, including the helicity of the emitted light and modulation bandwidth. We provide guidance for an optimized design of scaled-down spin- lasers. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M58.00009: Delocalization of Ubiquitous, Ultra-Sharp dd Excitations in Ni2+-based van der Waals Magnets Probed with Resonant Inelastic X-ray Scattering Connor A Occhialini, Yi Tseng, Qian Song, Mark Blei, Sefaattin Tongay, Valentina Bisogni, Jonathan Pelliciari, Riccardo Comin Excitons are fundamental quasiparticles in the study of light-matter coupling of particular interest in van der Waals (vdW) semiconductors. Significant efforts have been given towards the study of novel excitations in magnetic vdW systems hosting Ni2+ions. Sharp peaks in optical experiments have been associated to spin-forbidden dd excitations, with a suggested excitonic character related to long-range magnetic order that is mediated by self-doped ligand holes. Significant evidence has been provided by resonant inelastic X-ray scattering (RIXS) experiments; however, this interpretation raises questions regarding the proposed excitonic delocalization mechanism and the true connection to long-range magnetism. Here, we investigate the electronic states of Ni2+ vdW magnets with Ni L3 edge high-resolution RIXS, focusing on the nickel dihalides NiX2 (X=Cl,Br,I). Variation of the halogen corresponds to tuning the covalency and the spin/orbital ground states, allowing us to assess the role of the ligand holes, electronic configuration and magnetism. We find near resolution-limited dd excitations of both 1A1g and 1Eg character are ubiquitous in the nickel dihalides and likely a general feature of Ni2+ systems. The role of ligand holes can be effectively mapped to a screening of the intra-atomic Hund’s coupling within a single-ion model. We further reveal characteristic temperature and, particularly, momentum dependencies of these excitations that are qualitatively similar across the dihalide series despite disparate magnetic ground states/transition temperatures. From these observations, we conclude that these excitations are independent of magnetic order and are localized dd transitions, likely coupled to distinct bosonic excitations, such as phonons. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M58.00010: Exciton-spin interaction in charge-transfer insulators Tatsuya Kaneko, Yuta Murakami, Denis Golez, Zhiyuan Sun, Andrew Millis We theoretically investigate the correlation between magnetism and exciton creation in antiferromagnets such as van der Waals material NiPS3 by deriving an effective model for exciton-spin interactions in charge-transfer insulators. We show that in these systems the spin exchange interaction around the exciton is strongly enhanced from the original interaction. The exciton behaves like the impurity in the antiferromagnetic background and the local spins related to the exciton site prefer to make the spin multiplet because of the strong spin interaction. We also consider the mobility of the exciton and discuss possible optically allowed excitation peaks associated with the exciton creation and modified spin structure. |
Wednesday, March 8, 2023 10:48AM - 11:00AM |
M58.00011: High Resolution Polar Kerr Effect Studies of CsV3Sb5 David Saykin, Camron Farhang, Erik D Kountz, Dong Chen, Brenden Ortiz, Chandra Shekhar, Claudia Felser, Stephen D Wilson, Ronny Thomale, Jing Xia, Aharon Kapitulnik We report high resolution polar Kerr effect measurements on CsV3Sb5 single crystals in search for signatures of spontaneous time reversal symmetry breaking below the charge order transition at T* = 94 K. Utilizing two different versions of zero-area loop Sagnac interferometers operating at 1550 nm wavelength, each with the fundamental attribute that without a time reversal symmetry breaking sample at its path, the interferometer is perfectly reciprocal, we find no observable Kerr effect to within the noise floor limit of the apparatus at 30 nanoradians. Simultaneous coherent reflection ratio measurements confirm the sharpness of the charge order transition in the same optical volume as the Kerr measurements. At finite magnetic field we observe a sharp onset of a diamagnetic shift in the Kerr signal at T*, which persists down to the lowest temperature without change in trend. Since 1550 nm is an energy that was shown to capture all features of the optical properties of the material that interact with the charge order transition, we are led to conclude that it is highly unlikely that time reversal symmetry is broken in the charge ordered state in CsV3Sb5. |
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