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, Van Quang Nguyen, Min Seop Kim, Sang Eon Lee, Hyebin Son, Heon Jung Kim, Jong Soo Rhyee, Vu Thi Hoa, 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. EllimanSang J. Park, Junseok Kim, Hyungyu Jin, Suk Ho Choi

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2 Citations (Scopus)

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 Bi0.96Sb0.04 thin films are reported. 2D weak anti-localization (WAL) and chiral anomaly arise in the Bi0.96Sb0.04 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 Bi0.96Sb0.04 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.

Original languageEnglish
Article number2305179
JournalAdvanced Functional Materials
Volume33
Issue number51
DOIs
Publication statusPublished - 15 Dec 2023

Bibliographical note

Publisher Copyright:
© 2023 Wiley-VCH GmbH.

Keywords

  • Dirac semimetal
  • Weyl semimetal
  • chiral anomaly
  • thickness
  • topological phase transition
  • weak anti-localization

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