Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S59: Weyl semimetals, magnetism and superconductivityFocus
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Sponsoring Units: DMP Room: Mile High Ballroom 3C |
Thursday, March 5, 2020 11:15AM - 11:27AM |
S59.00001: Reorientation of antiferromagnetism in Co-doped FeSn and its implications for Dirac electron states William Meier, Jiaqiang Yan, Michael McGuire, Xiaoping Wang, Andrew D Christianson, Brian Sales FeSn is an itinerant antiferromagnet with an Fe Kagome-lattice that hosts electronic Dirac states[1-2]. I will present magnetization measurements of single crystals of (Fe1-xCox)Sn revealing the evolution and suppression of this magnetic order with Co substitution. We interpret the dramatic changes of the magnetic anisotropy to indicate a reorientation of the magnetic moments from perpendicular to parallel to the hexagonal c-axis and confirm this with neutron diffraction. It has been proposed that the Dirac nodes observed in FeSn should become gapped if the moments rotate as our data suggests[1]. We identify Co-substituted compositions that adopts both antiferromagnetic configurations at different temperatures. This system provides a unique opportunity to study how the details of magnetic order impact Dirac electron states. |
Thursday, March 5, 2020 11:27AM - 11:39AM |
S59.00002: Above-room-temperature ferromagnetic state in a proximitized topological Dirac semimetal Masaki Uchida, Takashi Koretsume, Shin Sato, Markus Kriener, Yusuke Nakazawa, Shinichi Nishihaya, Yasujiro Taguchi, Ryotaro Arita, Masashi Kawasaki We report an above-room-temperature ferromagnetic state realized in a proximitized Dirac semimetal, which is fabricated by growing typical Dirac semimetal Cd3As2 films on a ferromagnetic garnet with strong perpendicular magnetization. Observed anomalous Hall conductivity with substantially large Hall angles is found to be almost proportional to the separation of the Weyl nodes and opposite in sign to magnetization, in agreement with a minimal model behavior. Theoretical calculations based on first-principles electronic structure of Cd3As2 also demonstrate that the Fermi-level dependent anomalous Hall conductivity reflects the Berry curvature originating in the split Weyl nodes. The present high-mobility Dirac-semimetal/ferromagnetic-insulator heterostructure will provide a novel platform for exploring Weyl-node transport phenomena and spintronic functions lately proposed for topological semimetals. |
Thursday, March 5, 2020 11:39AM - 12:15PM |
S59.00003: Interplay of magnetic frustration and topology in complex metals Invited Speaker: James Analytis The interplay of topology and frustration can lead to exotic properties and physical phenomena. We study how signatures of topological transport properties can be affected by complex magnetic textures in Kagome and triangular lattice materials. As an example, we show in the case of Co3Sn2S2 that the presence of frustration leads to coexsiting magnetic phases that drive an exchange biased anomalous Hall effect. We also study novel transport anisotropies and magnetoelectric coupling in microstuctured devices. |
Thursday, March 5, 2020 12:15PM - 12:27PM |
S59.00004: Introducing ferromagnetism into Dirac semimetal Cd3As2 thin films Run Xiao, Arpita Mitra, Wilson Yanez, Jacob T Held, Michelle Tomczyk, Fan Zhang, Yawen Fang, K. Andre Mkhoyan, Brad J Ramshaw, Nitin Samarth Breaking time-reversal symmetry in a Dirac semimetal (DSM) via magnetic doping is expected to create a Weyl semimetal. This motivates us to study the doping of the DSM Cd3As2 using transition metals. Here, we attempt to introduce Mn into Cd3As2 thin films grown by molecular beam epitaxy on GaAs (111)B substrates with a GaSb buffer layer. Atomic force microscopy and X-ray diffraction show that the films have good crystalline quality (root mean square surface roughness ~ 1.5 nm and full-width half maximum of rocking curves ~ 0.12°). However, cross-sectional scanning transmission electron microscopy indicates constraints on Mn incorporation and the formation of magnetically inhomogeneous films with a near-surface Mn-rich compound. SQUID magnetometry shows the presence of weak ferromagnetism. We use low-temperature transport measurements in patterned devices as a function of gate voltage, temperature, and magnetic field angle to understand Shubnikov-de Haas oscillations and quantum transport in this hybrid Dirac material. |
Thursday, March 5, 2020 12:27PM - 12:39PM |
S59.00005: Tunable Berry Curvature Effects Through Volume-wise Magnetic Competition in a Topological Kagome Magnet Co3Sn2S2 Zurab Guguchia, Joel Verezhak, Dariusz Gawryluk, Stepan Tsirkin, Jiaxin Yin, Ilya Belopolski, Huibin Zhou, Gediminas Simutis, Songtian Zhang, Tyler Cochran, Guoqing Chang, Ekaterina Pomjakushina, Lukas Keller, Zuzanna Skrzeczkowska, Qi Wang, Hechang Lei, Rustem Khasanov, Alex Amato, Shuang Jia, Titus Neupert, Hubertus Luetkens, Zahid Hasan Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several |
Thursday, March 5, 2020 12:39PM - 12:51PM |
S59.00006: Observation of an edge supercurrent in Weyl semimetal MoTe2 Wudi Wang, Stephan Kim, Minhao Liu, F. Alexandre Cevallos, Robert J. Cava, N. Phuan Ong We report evidences and interpretations for a robust edge supercurrent in type II Weyl semimetal MoTe2 in the superconducting regime, where T < Tc = 100 mK at ambient pressure. We fabricated MoTe2 devices (60 – 120 nm thickness) with Au contacts through mechanical exfoliation and nanofabrication. Transport measurements of differential resistance dV/dI versus applied bias and magnetic field B shows a periodic oscillation of critical current Ic with a scalloped profile. The oscillation mode remains coherent and the associated area to its frequency saturates to the physical area of sample with an increasing magnetic field. These observations demonstrate a superconducting edge mode with the width less than 10 nm. We describe the edge condensate with a Ginzburg Landau wave function that is independent from the bulk condensate. Fluxoid quantization causes the edge superfluid velocity to vary, resulting in the scalloped profile. Weak excitations trailing from the scalloped boundaries in Ic vs. B plots exhibit unusual asymmetries. |
Thursday, March 5, 2020 12:51PM - 1:27PM |
S59.00007: Magnetic Weyl Semimetals Invited Speaker: Claudia Felser Topology a mathematical concept became recently a hot topic in condensed matter physics and materials science. One important criteria for the identification of the topological material is in the language of chemistry the inert pair effect of the s-electrons in heavy elements and the symmetry of the crystal structure [1]. Beside of Weyl and Dirac new fermions can be identified compounds via linear and quadratic 3-, 6- and 8- band crossings stabilized by space group symmetries [2]. In magnetic materials the Berry curvature and the classical AHE helps to identify interesting candidates. Magnetic Heusler compounds were already identified as Weyl semimetals such as Co2YZ [3-6] (Y=Ti, Mn; Z=Ge, Sn, Ga, Al), in Mn3Z [7-9] (Z=Ge, Sn). Co3Sn2S2 is a 2D Weyl semimetal with edge states [11-12]. |
Thursday, March 5, 2020 1:27PM - 1:39PM |
S59.00008: Electronic, magnetic and thermodynamic properties of the Kagome layer metal FeSn Brian Sales, Jiaqiang Yan, William R Meier, Qiang Zheng, Andrew D Christianson, Satoshi Okamoto, Michael McGuire FeSn is an itinerant antiferromagnet composed of metallic Kagome layers. FeSn single crystals are investigated using x-ray and neutron scattering, magnetic susceptibility and magnetization, heat capacity, resistivity, Hall, Seebeck, thermal expansion, thermal conductivity measurements and density functional theory. In spite of the quasi 2D Kagome layers with Dirac nodal lines along the K-H directions in the magnetic Brillouin zone about 0.3 eV below the Fermi energy, the measured properties strongly suggest that the overall electronic structure is 3D. The magnetism, however, is predicted to be highly 2D with Jin-plane/Jout-of-plane ≈ 10. The impact of Dirac nodes on the physics on this material will be discussed. |
Thursday, March 5, 2020 1:39PM - 1:51PM |
S59.00009: Low temperature investigation of candidate type-II Weyl semimetal LaAlGe Mark Zic, Chris Eckberg, Halyna Hodovanets, Seokjin Bae, Hyunsoo Kim, Tristin Metz, Sean Winters, Daniel Kraft, Steven Anlage, Johnpierre Paglione Weyl semimetals continue to be a flourishing topic of research because of their non-trivial surface states and topology [1] and their exciting experimental realizations in magnetotransport [2], thermopower [3], and optical spectroscopy [4]. These unique ground states motivate us to investigate the proposed Weyl semimetal LaAlGe [5], a compound previously only investigated theoretically and with X-ray diffraction. |
Thursday, March 5, 2020 1:51PM - 2:03PM |
S59.00010: Magnetostructural instability in Weyl ferromagnet Mn3ZnC Samuel Teicher, Ida K Svenningsson, Leslie Schoop, Ram Seshadri We present first-principles calculations suggesting that the ferromagnetic phase of cubic antiperovskite Mn3ZnC is a nodal line Weyl semimetal. Electronic structure features that are the hallmark of this nodal line state—a large density of linear band crossing near the Fermi level—can also be interpreted as signatures of structural and magnetic instability. In fact, it is known that Mn3ZnC transitions upon cooling from a paramagnetic to a cubic ferromagnetic state under ambient conditions and then further into a non-collinear tetragonal phase at a temperature between 250 K and 200 K. The existence of Weyl nodes and their destruction via structural and antiferromagnetic ordering is likely relevant to a range of magnetostructurally coupled materials. |
Thursday, March 5, 2020 2:03PM - 2:15PM |
S59.00011: Ultrasound Studies on the Chiral Antiferromagnet Mn3Ge Florian Theuss, Sayak Ghosh, Taishi Chen, Satoru Nakatsuji, Brad J Ramshaw The chiral antiferromagnet Mn3Ge is a promising candidate for a magnetic Weyl semimetal, where Weyl nodes arise from broken time reversal symmetry rather than broken inversion symmetry. Recently, Mn3Ge has been shown to exhibit a giant anomalous Hall effect at room temperature, which has been attributed to the presence of Weyl nodes. Given this highly anomalous room-temperature Hall effect, it is natural to ask whether other properties of the Weyl nodes, such as the chiral anomaly, are also present at room temperature. Strong magneto-elastic coupling, known to be present in Mn3Ge, has motivated our investigation of the elastic moduli in this material. We report resonant ultrasound spectroscopy studies of the full elastic tensor of Mn3Ge through the 380 K Néel transition temperature. We investigate how strains of different symmetry couple to the magnetic degrees of freedom on the Kagome lattice formed by manganese ions. We also investigate ultrasonic attenuation - which is predicted to be highly sensitive to chiral charge pumping between Weyl nodes in a magnetic field - both above and below the Néel transition. |
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