Broadband transient THz conductivity of the transition-metal dichalcogenide MoS2

J. H. Buss; R. P. Smith; G. Coslovich; R. A. Kaindl

doi:10.1117/12.2080748

14 March 2015 Broadband transient THz conductivity of the transition-metal dichalcogenide MoS₂

J. H. Buss, R. P. Smith, G. Coslovich, R. A. Kaindl

Proceedings Volume 9361, Ultrafast Phenomena and Nanophotonics XIX; 93611F (2015) https://doi.org/10.1117/12.2080748
Event: SPIE OPTO, 2015, San Francisco, California, United States

Abstract

The transient dynamics of transition-metal dichalcogenides is of significant interest for clarifying fundamental manyparticle interactions at the nanoscale as well as for novel applications. We report an ultrafast terahertz study up to 7 THz of the lamellar semiconductor MoS₂ to access the non-equilibrium conductivity of photo-excited indirect e-h pairs in this multi-layered parent compound. While the equilibrium transport is Drude-like, near-IR optical excitation results in a complex photo-induced conductivity that consists of two components. Mobile charge carriers dominate the low frequency response below 2 THz, while at low temperatures an additional excess conductivity is observed that is enhanced around 4 THz. Two time scales appear in the dynamics: a slow ns relaxation due to non-radiative recombination and a faster sub-100 ps decay connected to the high-frequency THz feature. We discuss the broad THz peak within a model of intra-excitonic transitions in MoS₂. It agrees well with the expected binding energy and oscillator strength, yet results in an anomalous temperature dependence of the exciton fraction requiring an electronically inhomogeneous phase.

Citation Download Citation

J. H. Buss, R. P. Smith, G. Coslovich, and R. A. Kaindl "Broadband transient THz conductivity of the transition-metal dichalcogenide MoS₂", Proc. SPIE 9361, Ultrafast Phenomena and Nanophotonics XIX, 93611F (14 March 2015); https://doi.org/10.1117/12.2080748

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