We have measured the terahertz (THz) conductance of a 23 quintuple layer thick film of bismuth selenide (Bi₂Se₃) and found signatures for topological surface states (TSSs) below 50 K. We provide evidence for a topological phase transition as a function of lattice temperature by optical means. In this work, we used THz time-domain spectroscopy (THz-TDS) to measure the optical conductance of Bi₂Se₃, revealing metallic behavior at temperatures below 50 K. We measure the THz conductance of Bi₂Se₃ as 10 e²/h at 4 K, indicative of a surface dominated response. Furthermore, the THz conductance spectra reveal characteristic features at ~1.9 THz attributed to the optical phonon mode, which is weakly visible at low temperatures but which becomes more prominent with increasing temperature. These results present a first look at the temperature-dependent behavior of TSSs in Bi₂Se₃ and the capability to selectively identify and address them using THz spectroscopy.

Date Published: 24 February 2017
PDF: 7 pages
Proc. SPIE 10103, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X, 101030D (24 February 2017); doi: 10.1117/12.2249587

Published in SPIE Proceedings Vol. 10103:
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X
Laurence P. Sadwick; Tianxin Yang, Editor(s)