Giant, unconventional anomalous Hall effect in the metallic frustrated magnet candidate, KV3Sb5.
Sci Adv 6:31 (2020)
Abstract:
The anomalous Hall effect (AHE) is one of the most fundamental phenomena in physics. In the highly conductive regime, ferromagnetic metals have been the focus of past research. Here, we report a giant extrinsic AHE in KV3Sb5, an exfoliable, highly conductive semimetal with Dirac quasiparticles and a vanadium Kagome net. Even without report of long range magnetic order, the anomalous Hall conductivity reaches 15,507 Ω-1 cm-1 with an anomalous Hall ratio of ≈ 1.8%; an order of magnitude larger than Fe. Defying theoretical expectations, KV3Sb5 shows enhanced skew scattering that scales quadratically, not linearly, with the longitudinal conductivity, possibly arising from the combination of highly conductive Dirac quasiparticles with a frustrated magnetic sublattice. This allows the possibility of reaching an anomalous Hall angle of 90° in metals. This observation raises fundamental questions about AHEs and opens new frontiers for AHE and spin Hall effect exploration, particularly in metallic frustrated magnets.Exchange bias in magnetic topological insulator superlattices
Nano Letters American Chemical Society 20:7 (2020) 5315-5322
Abstract:
Magnetic doping and proximity coupling can open a band gap in a topological insulator (TI) and give rise to dissipationless quantum conduction phenomena. Here, by combining these two approaches, we demonstrate a novel TI superlattice structure that is alternately doped with transition and rare earth elements. An unexpected exchange bias effect is unambiguously confirmed in the superlattice with a large exchange bias field using magneto-transport and magneto-optical techniques. Further, the Curie temperature of the Cr-doped layers in the superlattice is found to increase by 60 K compared to a Cr-doped single-layer film. This result is supported by density-functional-theory calculations, which indicate the presence of antiferromagnetic ordering in Dy:Bi2Te3 induced by proximity coupling to Cr:Sb2Te3 at the interface. This work provides a new pathway to realizing the quantum anomalous Hall effect at elevated temperatures and axion insulator state at zero magnetic field by interface engineering in TI heterostructures.Pressure-Induced Topological and Structural Phase Transitions in an Antiferromagnetic Topological Insulator**Supported by the National Key Research and Development Program of China under Grant Nos. 2018YFA0704300 and 2017YFE0131300, the National Natural Science Foundation of China under Grant Nos. U1932217, 11974246, 11874263 and 10225417, and the Natural Science Foundation of Shanghai under Grant No. 19ZR1477300. The authors thank the support from Analytical Instrumentation Center (SPST-AIC10112914), SPST, ShanghaiTech University. This work was partially supported by Collaborative Research Project of Materials and Structures Laboratory, Tokyo Institute of Technology, Japan. Part of this research is supported by COMPRES (NSF Cooperative Agreement EAR-1661511).
Chinese Physics Letters IOP Publishing 37:6 (2020) 066401
Signature for non-Stoner ferromagnetism in the van der Waals ferromagnet Fe3GeTe2
Physical Review B American Physical Society (APS) 101:20 (2020) 201104
Electronic structure and spatial inhomogeneity of iron-based superconductor FeS**Project supported by CAS-Shanghai Science Research Center, China (Grant No. CAS-SSRC-YH-2015-01), the National Key R&D Program of China (Grant No. 2017YFA0305400), the National Natural Science Foundation of China (Grant Nos. 11674229, 11227902, and 11604207), the EPSRC Platform Grant (Grant No. EP/M020517/1), Hefei Science Center, Chinese Academy of Sciences (Grant No. 2015HSC-UE013), Science and Technology Commission of Shanghai Municipality, China (Grant No. 14520722100), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB04040200).
Chinese Physics B IOP Publishing 29:4 (2020) 047401