Ultrafast Dynamics of Bi1.5Sb0.5Te1.8Se1.2 Topological Insulator

ORAL

Abstract

Bi1.5Sb0.5Te1.8Se1.2~(BSTS) is a type of topological insulator, which is an insulator in bulk but surface states are gapless. In this work, we took optical pump-probe data on BSTS crystal to analyze the dynamics of phonons and charge carriers. The ultrafast dynamics were obtained as a function of temperature ranging from 10K to 300K, as well as fluence ranging from 1 $\mu $J/cm2 to 10 $\mu $J/cm2. In additional to the coherent optical phonon mode found in other topological insulators, acoustic phonon mode was observed in our experiment. We also observed phonon softening and the temperature dependence of carrier lifetime in BSTS.

*Singapore NRF RCA-08/018 and NRF-CRP4-2008-04; Singapore MOE AcRF Tier 1 RG 13/12, Tier 2 MOE2010-T2-2-059 and ARC 23/08; NNSA of US DOE at LANL under Contract No. DE-AC52-06NA25396, and in part by LANL CINT, a US DOE Office of BES user facility.

–

Authors

  • Liang Cheng

    • Nanyang Tech Univ

  • Chi-Sin Tang

    • Nanyang Tech Univ

  • Saritha Krishnankutty Nair

    • Nanyang Tech Univ

  • Bin Xia

    • Nanyang Tech Univ

  • Lan Wang

    • Nanyang Tech Univ

  • Jian-Xin Zhu

    • Los Alamos National Laboratory
    • Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory
    • Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
    • Theoretical Division and Center for Integrated Technologies, Los Alamos National Laboratory
    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory
    • Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
    • Los Alamos National Lab
    • Theoretical Division and Center for Nonlinear Studies, LANL, Los Alamos, New Mexico 87545, USA
    • Los Alamos Natl Lab

  • Ee Min Elbert Chia

    • Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
    • Nanyang Tech Univ