Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session P41: Spins in Nonmagnetic Semiconductors 
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Sponsoring Units: GMAG DMP FIAP DCOMP Chair: Raphael Daveau, Cornell University Room: 707 
Wednesday, March 4, 2020 2:30PM  2:42PM 
P41.00001: Band structure probe of near Surface InAs Quantum Wells Brenden A Magill, Giti Khodaparast, Sunil K Thapa, Christopher J Stanton, Joseph Yuan, Mehdi Hatefipour, William Mayer, Matthieu Dartiailh, Kasra Sardashti, Kaushini S Wickramasinghe, Javad Shabani, Y. H. Matsuda, Zhuo Yang, Yoshimitsu Kohama Near surface InAs quantum wells (QW) have recently attracted a great deal of interest as tools to explore mesoscopic and topological superconductivity. These shallow QWs can interact strongly with superconducting layers which can be epitaxially grown on their surfaces. In this talk, we present a combined experimental and theoretical approach to study the band structure of these QWs. The effective mass and gfactors in these QWs were determined using high field cyclotron resonance (CR). Unlike GaAs, narrow gap systems like InAs have large nonparabolicity in their band structures.The band parameters extracted from our CR experiments are consistent with those obtained from Shubnikov de Hass measurements and agree remarkably well with the theoretical calculations. Our band structure models include strong mixing of the conduction and valence bands which leads to a large nonparabolicity. The calculations accurately describe the experimental observations and allowing us to accurately map the effective mass and gfactor as a function of magnetic field, Landau level index, and the well width for different near surface InAs QWs. 
Wednesday, March 4, 2020 2:42PM  2:54PM 
P41.00002: Weakantilocalization Induced by Spinorbit Interaction in Twodimensional Tellurium Chang Niu, Zhuocheng Zhang, Gang Qiu, Yixiu Wang, Wenzhuo Wu, Peide (Peter) Ye Tellurium (Te) is an intrinsic ptype semiconductor with a narrow bandgap of 0.35eV, whose hexagonal crystal structure is formed by van der Waals interaction between each helical atom chains. Through controllable atomic layer deposition (ALD) grow dielectric doping, we can access transport properties of Te conduction band. Here we report experimental results regarding weakantilocalization (WAL) effect in ntype twodimensional (2D) Te films at cryogenic temperatures. The gate and temperature dependence on WAL shows D'yakonovPerel (DP) mechanism plays the main role in spin relaxation and electronelectron (ee) interaction is dominant for phase relaxation, which matches well with Iordanskii, LyandaGeller, and Pikus (ILP) theory. Also, phase coherence length of Te extracted from WAL feature reaches 573nm at T=1K and transition from weaklocalization (WL) to weakantiocalization (WAL) is observed by tuning the gate bias, indicating its potential for future tunable spintronic applications. 
Wednesday, March 4, 2020 2:54PM  3:06PM 
P41.00003: Magnetooptical properties of ntype InAsP films in ultrahigh magnetic fields Sunil K Thapa, Christopher J Stanton, Brenden A Magill, Rathsara R Herath Mudiyanselage, Giti Khodaparast, Y. H. Matsuda, Zhuo Yang, Yoshimitsu Kohama, Sukgeun Choi, Chris J Palmstrom InAsP ternary alloys have immense prospect for optoelectronic and quantum communication devices due to their variable band gap of 0.351.35 eV and tunability in the gfactors. We present a theoretical/experimental study of the magnetooptical properties of ntype InAs_{x}P_{1−x} films (x=0.07,0.34) in ultrahigh magnetic fields in the Faraday’s geometry at T=300 K using k.p method with modified 8band PidgeonBrown model. The calculated Landaulevel Fan diagram for x=0.34 suggests a nearzero gfactor. Moreover, the Fielddependent Fermi levels and the absorption coefficients show a very strong corroboration with the Cyclotron Resonance (CR) measurements, both in position and the strength. In this study, we also employed ultrafast Time Resolved Differential Reflectivity (TRDR) and ultrafast time resolved Magnetooptic Kerr Effect (MOKE) to provide information on the carrier and spin relaxation dynamics. 
Wednesday, March 4, 2020 3:06PM  3:18PM 
P41.00004: Ultralong spin coherence in MAPbI_{3} single crystals revealed by ultrafast optics Yue Yao, Matthew Sheffield, Heshan Hewa Walpitage, Isaac P Brown Heft, Ye Liu, Zhenyi Ni, Jinsong Huang, Yan Li Hybrid organicinorganic perovskites (HOIPs) have demonstrated remarkable optoelectronic properties with their unprecedented rate of increase in solar cell efficiency, and their applications have been quickly extended to many areas, including light emitting diodes, lasing, and photo detection. Recent studies have also revealed their great potential in spintronics because of spindependent optical transitions, long spin lifetimes, and predicted large spinorbit coupling effects for potential spin manipulation. Our previous study revealed long spin lifetimes (T_{2}^{*}) exceeding 1 ns at 4 K on MAPbI_{3} polycrystalline films despite the presence of large spinorbit coupling. Here, in order to exclude the influence of the polycrystalline structure and obtain intrinsic spin dynamics, we investigate spin dynamics on high quality MAPbI_{3} single crystals by timeresolved Faraday rotation (TRFR). The spin lifetime improved by an order of magnitude when compared to polycrystalline films, which suggests the long spin lifetime is an intrinsic property of MAPbI_{3}. Combining the TRFR measurements with circularlypolarized photoluminescence, we analyze the interplay between carrier dynamics and spin dynamics upon optical excitation of spinpolarized carriers in this HOIP. 
Wednesday, March 4, 2020 3:18PM  3:30PM 
P41.00005: Probing the cubic crystal anisotropy and spinorbit interaction in GaAs heterostructures using hole quantum point contacts Karina Hudson, Ashwin Srinivasan, Dmitry Miserev, Qingwen WANG, Oleh Klochan, Ian Farrer, David A Ritchie, Alex Hamilton Understanding the form of the spinorbit interaction (SOI) in semiconductors such as GaAs is a prerequisite for engineering of topological superconducting and insulating states in these materials. Zeeman spinsplitting transport measurements in ptype 1D quantum point contacts (QPCs) are an effective probe of the SOI. Previous measurements have shown that there is a strong anisotropy in the inplane gfactors in hole QPCs due to SOI (g_{}I > g⊥I), which can be explained as arising from a second k^{4}B Zeeman term in addition to the established k^{2}B Zeeman term^{1}. 
Wednesday, March 4, 2020 3:30PM  3:42PM 
P41.00006: Origin of RashbaDresselhaus effect in a Pbfree ferroelectric nitride perovskite. Subhadeep Bandyopadhyay, Indra Dasgupta First principles electronic structure calculations have been employed to investigate the RashbaDresselhaus spin splitting of the bands in a Pbfree nontoxic ferroelectric nitride perovskite. Our first principles results are supplemented with effective k.p model analysis. A systematic study of orthorhombic and rhombohedral phases of this system reveal the importance of symmetry in realizing the nature of the splitting of bands around the time reversal invariant kpoints. In the orthorhombic structure it shows linear RashbaDresselhaus splitting where nonsymmorphic symmetries play an important role in enhancing the band splitting in the k_{z} = π/c plane. While the rhombohedral phase shows existence of unique higher order RashbaDresselhaus term which mixes with the linear RashbaDresselhaus term to produce unusual pattern of outofplane spin component in the spin texture that may find application in spintronics. 
Wednesday, March 4, 2020 3:42PM  3:54PM 
P41.00007: Efficient spin to charge conversion at strained amorphousSi thin film interfaces Ravindra G Bhardwaj, Anand Katailiha, Paul C Lou, Sandeep Kumar Interfacial asymmetry in conjunction with strain engineering can provide an alternate pathway to achieve efficient and controllable spin to charge conversion. This hypothesis is experimentally verified using spinSeebeck effect measurement in case of Bdoped amorphousSi thin film interface. The spinSeebeck voltage and spinHall angle in amorphousSi is found to be an order of magnitude larger than the corresponding value for Pt thin film spin detector. Further, the spinSeebeck effect is greatly enhanced in the multilayer heterostructures and it diminishes when the strain effects in the sample are reduced. The inhomogeneous strain induces strong interfacial RashbaDresselhaus spinorbit coupling in the twodimensional electron gas at the metalSi interface. The resulting intrinsic inverse spinHall effect is the underlying cause of efficient spin to charge conversion, which is of the same order as the topological surface states. This study gives a new direction of research for spincaloritronics applications using strain engineering and amorphous materials. 
Wednesday, March 4, 2020 3:54PM  4:06PM 
P41.00008: Dephasing in quasi1D wires: NonMarkovian noise and correlations due to itinerant spin interactions Matthew Foster, Seth M Davis Motivated by the interest in manybody localization, we revisit the problem of dephasing due to electronelectron scattering in quasi1D (many channel) wires. The effectively Markovian bath due to Coulomb interactions dephases at any nonzero temperature [1]. The effect of shortranged (e.g. spin exchange) electronelectron scattering is more subtle. The latter induces a nonMarkovian, diffusive noise kernel. Formally the field theory describing the dephasing in the presence of a purely diffusive bath has an upper critical spatial dimension of d = 4, and is strongly coupled in d = 1 [2]. We show that a perturbative expansion in the diffusive noise kernel is welldefined but unphysical at long times. We also consider the case of both Coulomb and spinexchange scattering, using the former to physically regularize the latter. In this case we find "rephasing" contributions at second order that are in contrast to the Markovian limit [3]. We discuss possible experimental signatures. 
Wednesday, March 4, 2020 4:06PM  4:18PM 
P41.00009: Radial spin texture in elemental tellurium with chiral crystal structure Masato Sakano, Motoaki Hirayama, Takanari Takahashi, Shuntaro Akebi, Mitsuhiro Nakayama, Kenta Kuroda, Kazuaki Taguchi, Tomoki Yoshikawa, Koji Miyamoto, Taichi Okuda, Kanta Ono, Hiroshi Kumigashira, Toshiya Ideue, Yoshihiro Iwasa, Mitsuishi Natsuki, Kyoko Ishizaka, Shik Shin, Takashi Miyake, Shuichi Murakami, Takao Sasagawa, Takeshi Kondo Trigonal tellurium has a chiral crystal structure which is characterized by a lack of mirror symmetry and an inversion center, resulting in the inequivalent right and lefthanded structures. To reveal the spin textures of chiral crystals, here we investigate the spin and electronic structure in ptype semiconductor elemental tellurium by using spin and angleresolved photoemission spectroscopy. Our data demonstrate that the highest valence band crossing the Fermi level has a spin component parallel to the momentum of electron around the Brillouin zone corners. Significantly, we have also confirmed that the spin polarization is reversed in the crystal with the opposite chirality. The results indicate that the spin textures of the right and lefthanded chiral crystals are hedgehoglike, leading to unconventional magnetoelectric effects and nonreciprocal phenomena. 
Wednesday, March 4, 2020 4:18PM  4:30PM 
P41.00010: Prediction of momentum dependent spin splitting in antiferromagnetic compounds without spinorbit coupling Linding Yuan, Zhi Wang, JunWei Luo, Alex Zunger The Conventional way of creating spin splitting entails the involvement of spin orbit coupling (SOC). The latter entails heavy elements that lead to weak bonds and undesirable defects. Can one generate spin splitting without relying on SOC? We identify the magnetic symmetry conditions that produce AFM prototypes having spin splitting even at TRIM points without external magnetic field and even when SOC is set to zero. The resulting spin splitting in AFM arises from the coupling between electron spin and the position coordinates which is k dependent and of the same order as the Thomas term. Band structures of specific compounds are worked out within DFT showing the effects. 
Wednesday, March 4, 2020 4:30PM  4:42PM 
P41.00011: Response of Bloch Electrons to Electric Fields William Kerr We consider the response of spinful Bloch electrons to external electric fields; the electrons’ unperturbed Hamiltonian is the one given by Dresselhaus [1], including the spinorbit interaction. We write matrices for the system observables with respect to the Bloch basis states of the unperturbed Hamiltonian, truncate them to two bands, and use them to obtain their Heisenberg equations of motion. The equation for the velocity contains not only the anomalous velocity term obtained by Karplus and Luttinger [2] [expressed in terms of the nowfamiliar (position operator) Berry connection [3]], but also additional terms involving “quasiconnections” from the momentum and spin operators. We apply the equations of motion resulting from this procedure to a twodimensional model of a ferromagnet with the Dresselhaus linearinwavevector spinorbit interaction and an exchange field term. We find for this model that the anomalous velocity is dominated by the term coming from the spin operator rather than the position operator. 
Wednesday, March 4, 2020 4:42PM  4:54PM 
P41.00012: Birefringent SpinLasers David Jiayu Cao, Gaofeng Xu, Velimir Labinac, Igor Zutic Introducing spinpolarized carriers in semiconductor lasers reveals an alternative path to realize roomtemperature spintronic applications, beyond the usual magnetoresistive effects[1]. Through carrier recombination, the angular momentum of the spinpolarized carriers is transferred to photons, thus leading to the circularly polarized emitted light. Surprisingly, a large birefringence[2], considered detrimental in both conventional and spinlasers, has been demonstrated to lead to ultrafast operation with an order of magnitude faster modulation frequency [3] than in the best commercial lasers. By using transparent rate equations we explain how the birefringence can provide key differences in the modulation frequency of the intensity and polarization of light emitted from a laser. We reveal that for such ultrafast operation it is important to have a short spin relaxation time in the active region of the semiconductor lasers, typically made of quantum wells. 
Wednesday, March 4, 2020 4:54PM  5:06PM 
P41.00013: Modeling of the MnCarrier Exchange Interaction in Colloidal CdSe/CdMnS Nanoplatelets with a Multilayer Core and Magnetically Doped Shell James Pientka, Arman Najafi, Steven Tarasek, Savas Delikanli, Peiyao Zhang, Tenzin Norden, Sushant Shendre, Manoj Sharma, Arinjoy Bhattacharya, Nima Taghipour, Hilmi Volkan Demir, Athos Petrou, Tim Thomay A Colloidal Nanoplatelet is a twodimensional semiconductor nanocrystal heterostructure that allows for wavefunction engineering by controlling their composition and or thickness. With the inclusion of a shell doped with magnetic ions around a nonmagnetic core, there exists a carrier mediated exchange interaction between the excitonic spin density and the Mn spins. Through the exchange interaction, magnetic effects such as Zeeman splitting and the excitonic photoluminescence circular polarization can be controlled by varying the shell thickness and or Mn content [1,2]. The previous works did not take into account on how the exitonic wavefunction is affected by the addition of the magnetically doped shell. Here, we present a model that includes the carrier mediated exchange interaction and study its effect on the excitonic wavefunction. [1] S. Delikanl et al.,ACS. Nano 2015 9, 12, 1247312479 [2] F. Muckel et al., Nano Lett. 2018, 18, 2047−2053. 
Wednesday, March 4, 2020 5:06PM  5:18PM 
P41.00014: Correlated States and Frustration in Magnetic Quantum Dots with Multiple Occupancy Tiago Campos, James Pientka, Alex Matos Abiague, Jong E Han, Igor Zutic Magnetically doped semiconductor quantum dots (QDs) provide an enhanced control of magnetic ordering as compared to their bulklike counterparts [1]. Unlike in the bulk structures, adding a single carrier in a magnetic QD can have important ramifications. An extra carrier can both strongly change the total carrier spin and the temperature of the onset of magnetization. Recent experiments reveal how multiple carrier occupancy is optically controlled in Mndoped IIVI QDs [2] and motivate studies of stronglycorrelated states in these systems. While Wigner molecules, as the nanoscale manifestation of correlation effects in Wigner crystals, have been extensively studied in nonmagnetic QDs, their generalizations in magnetic QDs are largely unexplored [3]. Using exact diagonalization and conditional probability density we reveal peculiar manifestations of stronglycorrelated states in Mndoped QDs. The spatial control of Mndopants provides a platform to examine the role of magnetic frustration and the shellstructure formation with the change in the strength of Coulomb interaction. 

P41.00015: Theory of Excitonic Phases in an ElectronHole DoubleLayer System with Relativistic SpinOrbit Interaction Yeyang Zhang, Ke Chen, Ryuichi Shindou We propose helicoidal and helical excitonic insulator phases in a Coulombcoupled twodimensional electronhole double layer (EHDL) system with relativistic spinorbit interaction. Previously, it was proposed that layered InAs/AlSb/GaInSb heterostructure is an ideal experimental platform for searching excitonic condense phases, while its electron layer has nonnegligible Rashba interaction. We clarify that due to the Rashba term, the spintriplet (spin1) and spinsinglet (spin0) excitonic fields in the EHDL system forms either helicoidal or helical structure, depending on its coupling with an inplane Zeeman field. We provide a comprehensive understanding of electric and magnetic properties of these condensed phases as well as their lowenergy collective modes. 
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