Publications associated with Thin Film Quantum Materials

Temperature evolution of topological surface states in Bi<inf>2</inf>Se<inf>3</inf> thin films studied using terahertz spectroscopy

Proceedings of SPIE - The International Society for Optical Engineering 10103 (2017)

VS Kamboj, A Singh, HE Beere, T Hesjedal, CHW Barnes, DA Ritchie

© 2017 SPIE. We have measured the terahertz (THz) conductance of a 23 quintuple layer thick film of bismuth selenide (Bi 2 Se 3 ) 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 Bi 2 Se 3 , revealing metallic behavior at temperatures below 50 K. We measure the THz conductance of Bi 2 Se 3 as 10 e 2 /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 Bi 2 Se 3 and the capability to selectively identify and address them using THz spectroscopy.

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