Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W70: Topology and Correlation: Magnetism, Superconductivity, and Flat BandsFocus Recordings Available
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Chair: Matthew Brahlek, Oak Ridge National Laboratory Room: Hyatt Regency Hotel -Jackson Park B |
Thursday, March 17, 2022 3:00PM - 3:36PM |
W70.00001: Tunable topological states with and without flat bands in semiconductor heterostructures Invited Speaker: Trithep Devakul Moiré heterostructures based on transition metal dichalcogenide bilayers have emerged in recent years as a new platform for strongly interacting physics in which strongly correlated and topologically non-trivial phases of matter have already been observed experimentally. |
Thursday, March 17, 2022 3:36PM - 3:48PM |
W70.00002: Molecular beam epitaxy of hexagonal Mn3Ge and its transport properties Deshun Hong, Gaurav Chaudhary, Changjiang Liu, Naween Anand, John Pearson, Anton Burkov, Olle Heinonen, Anand Bhattacharya The chiral antiferromagnet Mn3Ge is believed to be a Weyl semimetal and is a promising candidate for realizing tunable topological properties with applications in antiferromagnetic spintronics, especially in thin films and heterostructures. We will present recent work on synthesizing Mn3Ge by molecular beam epitaxy (MBE). Without using any conducting buffer layer, c-axis oriented Mn3Ge film can be epitaxially grown on LaAlO3 (111) with atomically smooth surfaces as indicated by in-situ reflection high energy electron diffraction (RHEED). These films can serve as model systems for studies of the surface states and interfacial properties. While the magnetization of our films is vanishingly small, a large anomalous Nernst signal has been observed. By rotating the antiferromagnetic structure in plane, the position of Weyl nodes can be varied in reciprocal space. We will present results on the angular dependence of both anisotropic magnetoresistance and anomalous Nernst effects, and generating spin-orbit torque using Mn3Ge to source spin currents in heterostructures with magnetic overlayers. |
Thursday, March 17, 2022 3:48PM - 4:00PM |
W70.00003: Epitaxial Growth of Kagome Ferromagnet Fe3Sn2 Shuyu Cheng, Igor Lyalin, Alexander Bishop, Binbin Wang, Nuria Bagues Salguero, David W McComb, Roland K Kawakami Kagome magnets are interesting due to the co-existence of Weyl points and spin frustration in these materials. The thin-film form of these materials is particularly desired for both fundamental research and practical application. Here we report the molecular beam epitaxy (MBE) growth of kagome magnet Fe3Sn2 on epitaxial Pt(111) buffer layer on Al2O3(0001) substrate. Using our unique atomic-layer MBE (AL-MBE) technique, we are able to grow these materials at a lower temperature, which reduces interdiffusion and generates a sharper interface. The structure of Fe3Sn2 is confirmed by a combination of reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and transmission electron microscopy (TEM), while the magnetic properties of Fe3Sn2 are demonstrated by magneto-optical Kerr effect (MOKE), SQUID magnetometry, and anomalous Nernst effect (ANE) imaging. |
Thursday, March 17, 2022 4:00PM - 4:12PM |
W70.00004: Induced Superconducting Pairing in Integer Quantum Hall Edge Modes of InAs Mehdi Hatefipour, Joseph J Cuozzo, Jesse S Kanter, William M Strickland, Tzu-Ming Lu, Enrico Rossi, Javad Shabani
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Thursday, March 17, 2022 4:12PM - 4:24PM |
W70.00005: Even-Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi2Te4 Thin Films Yifan Zhao, Ling-Jie Zhou, Fei Wang, Guang Wang, Tiancheng Song, Dmitry Ovchinnikov, Hemian Yi, Ruobing Mei, Ke Wang, Moses H Chan, Chaoxing Liu, Xiaodong Xu, Cui-Zu Chang A central theme in condensed matter physics is to create and understand the exotic states of matter by incorporating magnetism into topological materials. One prime example is the quantum anomalous Hall (QAH) state. Recently, MnBi2Te4 has been demonstrated to be an intrinsic magnetic topological insulator and the QAH effect was observed in exfoliated MnBi2Te4 flakes. In this work, we used molecular beam epitaxy (MBE) to grow MnBi2Te4 films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a non-square hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. Through careful analysis, we demonstrated that one AH component with the larger coercive field is from the dominant MnBi2Te4 phase, while the other AH component with the smaller coercive field is from a trace of Mn-doped Bi2Te3 phase in the samples. The extracted AH component of the MnBi2Te4 phase shows a clear even-odd layer-dependent behavior, a signature of antiferromagnetic thin films. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi2Te4 films, in which the QAH and other exotic states are predicted. |
Thursday, March 17, 2022 4:24PM - 4:36PM Withdrawn |
W70.00006: Tricritical phenomena in magnetic Wyle semimetals AMnP (A: Zr, Hf) Tej N Lamichhane, Mingda Li AMnP (A: Zr, Hf) are recently identified topological nodal line magnetic Wyle semimetals with the topological states protected with vertical mirror symmetry[1]. Their low-temperature Arrott plots were used to confirm the easy axis of magnetization and high-temperature Arrott plots were reported only for ZrMnP before[2]. From the preliminary speculation of data, ZrMNP was identified strictly following mean-field theory in its tricritical exponents whereas HfMnP single crystalline samples exponent data were relatively difficult to access due to smaller crystal sizes and irregular surfaces to perfectly mount on the required surfaces. We will investigate the larger crystal growth techniques for these compounds and investigate further physical properties. In this talk, we will report a comparison of tricritical exponents of Ferro to paramagnetic transition in these systems and investigate the potential role of higher spin-orbit interaction in HfMnP to understand the deviation with ZrMnP if there exist any. |
Thursday, March 17, 2022 4:36PM - 4:48PM |
W70.00007: Growth and Characterization of Metamagnetic Transitions in Gd2PdSi3 Gabriel Perko-Engel, Daria Balatsky, sarah a schwarz, James G Analytis Recent work has drawn attention to the apparent magnetic skyrmion lattice behavior in Gd2PdSi3. In intermediate fields, it displays substantially larger Hall resistivity than most other known magnetic skyrmion materials. We discuss the growth of Gd2PdSi3 and the use of resonant ultrasound spectroscopy to probe the symmetry of its metamagnetic phase transitions. With RUS we can determine a substance’s elastic moduli from its mechanical resonances. As the material undergoes a phase transition, the response of the different elastic moduli reveals the symmetry of the order parameter. By further characterizing Gd2PdSi3’s symmetries, we hope to further our understanding of its skyrmionic behavior. |
Thursday, March 17, 2022 4:48PM - 5:00PM |
W70.00008: In-situ fabrication and magneto-transport properties of (111) oriented Y2Ir2O7 epitaxial thin film Tsung-Chi Wu, Xiaoran Liu, Fangdi Wen, Evguenia Karapetrova, Jong-Woo Kim, Philip J Ryan, John W Freeland, Michael Terilli, Mikhail S Kareev, Jak Chakhalian The interplay between topological phases and strong electronic correlations can induce novel phases of matter, which can push forward our understanding of many-body quantum phenomena. However, presently there is a scarcity of materials candidates that possess correlated electrons entwined with non-trivial band topology. Here, we report on the first successful fabrication of (111) oriented thin films of pyrochlore iridate Y2Ir2O7, a magnetic topological material candidate, employing solid phase epitaxy. Towards this, we have developed all in situ growth and annealing protocol, which is superior to the established ex-situ route that requires multi-hour annealing to stabilize the proper pyrochlore structure. The excellent morphological quality of the films with a pure pyrochlore phase has been confirmed. The magnetotransport properties regarding its Weyl semimetallic nature have been studied. These findings reveal the system presents an interplay of the Weyl semi-metallic phase, weak anti-localization effect, and the non-collinear antiferromagnetic ordering. |
Thursday, March 17, 2022 5:00PM - 5:12PM |
W70.00009: Experimental study of transport properties of Weyl semimetal LaAlGe thin films Niraj Bhattarai, Andrew W Forbes, Christopher Gassen, Raghad S.H. Saqat, Ian L Pegg, John Philip Rare earth compounds display diverse electronic, magnetic, and magneto-transport properties. Recently these compounds of the type RAlGe (R = La, Ce, Pr) have been shown to exhibit Weyl semimetallic behavior. In this work, we have grown and investigated the crystal structure, electronic, and magneto-transport properties of the Weyl semimetal LaAlGe thin films. As-grown films showed uniform surface topography and near ideal stoichiometry with a body-centered tetragonal crystal structure. The temperature dependence of longitudinal resistivity at different magnetic fields are discussed. Observations of magnetoresistances and the Hall effect at different temperatures and their evolution with magnetic field up to 6 T are also discussed with relevant mechanisms. We have observed positive unsaturated magnetoresistances, with a small quadratic contribution at low temperatures, which tends to saturate at higher fields. Our findings through various experimental investigations confirm the semi metallic nature of these films with an average charge carrier density of ~ 9.68×1021 cm-3 at room temperature. |
Thursday, March 17, 2022 5:12PM - 5:24PM |
W70.00010: Dynamical study of the origin of the charge density wave in AV3Sb5 (A=K, Rb, Cs) compounds Andrzej Ptok, Aksel Kobiałka, Malgorzata Sternik, Jan Lazewski, Pawel T Jochym, Andrzej M Oles, Przemyslaw Piekarz Systems containing the ideal kagome lattice can exhibit several distinct and novel exotic states of matter. One example of such systems is a recently discovered AV3Sb5 (A = K, Rb, and Cs) family of compounds. Here, the coexistence of the charge density wave (CDW) and superconductivity is observed. Here, we study the dynamic properties of the AV3Sb5 systems in context of origin of the CDW phase. We show and discuss the structural phase transition from P6/mmm to C2/m symmetry that are induced by the presence of phonon soft modes. We conclude that the CDW observed in this family of compounds is a consequence of the atom displacement, from the high symmetry position of the kagome net, in low-temperature phase. Additionally, using the numerical ab initio (DFT) methods, we discuss the charge distribution on the AV3Sb5 surface. We show that the observed experimental stripe-like modulation of the surface, can be related to surface reconstruction and manifestation of the three dimensional 2x2x2 bulk CDW. Finally, the consequence of realization of the C2/m structure on the electronic properties are discussed. We show that the electronic band structure reconstruction and the accompanying modification of density of states correspond well to the experimental data. |
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