2D Weyl‐Semimetal States Achieved by a Thickness‐Dependent Crossover and Topological Phase Transition in Bi0.96Sb0.04 Thin Films
Chan Wook Jang, Yusuff Adeyemi Salawu, Jin Hee Kim, Văn Quảng Nguyễn, Min Seop Kim, Sang‐Eon Lee, Hyebin Son, Heon‐Jung Kim, Jong‐Soo Rhyee, Thi Hoa Vu, Sunglae Cho, Jong Seok Lee, Myung‐Hwa Jung, Won Hyuk Shon, Tae Jin Jeong, Sung Kim, Han‐Yup Yum, Jung Ho Kim, Xiaolin Wang, R. G. Elliman, Sang J. Park, Junseok Kim, Hyungyu Jin, Suk‐Ho Choi
IF 18.5 (2023)
Advanced Functional Materials
Abstract Despite theoretical expectations for 2D Weyl semimetals (WSMs), realizing stable 2D topological semimetal states experimentally is currently a great challenge. Here, 2D WSM states achieved by a thickness‐dependent topological phase transition from 3D Dirac semimetal to 2D WSM in molecular‐beam‐epitaxy‐grown Bi 0.96 Sb 0.04 thin films are reported. 2D weak anti‐localization (WAL) and chiral anomaly arise in the Bi 0.96 Sb 0.04 films for thicknesses below ≈10 nm, supporting 2D Weyl semimetallic transport in the films. This is particularly evident from magnetoresistance (MR) measurements which show cusp structures at around B = 0, indicating WAL, and negative MR, typical of chiral anomaly, only for layers with thicknesses below ≈10 nm. The temperature dependencies of the dephasing length for various thicknesses are consistent with those of the MR. Analysis based on second harmonic generation, terahertz emission, Seebeck/Hall effects, Raman scattering, X‐ray diffraction, and X‐ray photoemission demonstrates that the Dirac‐ to Weyl‐semimetal phase transition for films thinner than ≈10 nm is induced by inversion‐symmetry breaking due to the lattice‐mismatch strain between the Bi 0.96 Sb 0.04 film and substrate. The realization of 2D WSMs is particularly significant for applications in high‐speed electronics, spintronics, and quantum computations due to their high mobility, chiral spin, and topologically‐protected quantum qubits.
https://doi.org/10.1002/adfm.202305179
Weyl semimetal
Semimetal
Condensed matter physics
Materials science
Berry connection and curvature
Spintronics
Magnetoresistance
Topology (electrical circuits)
Geometric phase
Physics
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