Pressure-Induced Structural and Electronic Topological Transitions in Bi<sub>1.5</sub>Sb<sub>0.5</sub>Te<sub>1.8</sub>Se<sub>1.2</sub> Alloy

ORAL

Abstract

Topological insulators (TIs) have surface states that are topologically protected against scattering or defects, and thus have been the subject of intense research. Among the A2B3 metal chalcogenide TIs, Bi1.5Sb0.5Te1.8Se1.2 quaternary alloy has been reported to have lowest bulk conductivity, being an optimal composition to study the surface transport properties. Here, using combined theoretical and experimental investigations, we show the hydrostatic pressure effects on the structural, vibrational and topological properties of the Bi1.5Sb0.5Te1.8Se1.2. Within pressure range up to 45 GPa, two structural phase transitions were observed; from R-3m phase to C2/m phase at ~13 GPa, and to disordered I4/mmm phase at ~22 GPa. Within the R-3m phase, several electronic transitions were also observed. Indirect bulk band gap transited to direct bulk band gap at ~5.8 GPa, and bulk gap closed with an appearance of Dirac semimetal (DSM) state at ~8.2 GPa. Anomaly in Full Width at Half Maximum (FWHM) of in-plane Raman peaks and c/a lattice constant ratio suggests contribution of electron-phonon coupling to the DSM transition.

*Department of Science and Technology (DST), INDIA, INSPIRE programme IF150848; U.S. Army RDECOM-Pacific FA5209-16-P-0090; U.S. Army Research Office W911NF-13-1-0364.

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Presenters

  • Joonseok Kim

    • Univ of Texas, Austin

Authors

  • Joonseok Kim

    • Univ of Texas, Austin

  • Rinkle Juneja

    • Materials Research Center, Indian Institute of Science

  • Nilesh Salke

    • Center for High Pressure Science and Technology Advanced Research

  • Witold Palosz

    • Brimrose Corporation

  • Venkataraman Swaminathan

    • U.S. Army RDECOM-ARDEC

  • Sudhir Trivedi

    • Brimrose Corporation
    • Brimrose Technology Corporation

  • Abhishek Singh

    • Materials Research Center, Indian Institute of Science
    • Material Reserach Centre, Indian Institute of Science Bengaluru
    • Materials Research Centre, Indian Institute of Science

  • Deji Akinwande

    • Univ of Texas, Austin
    • Department of Electrical and Computer Engineering, University of Texas at Austin

  • Jung-Fu Lin

    • Univ of Texas, Austin
    • Department of Geological Sciences, University of Texas at Austin