Excitation and Relaxation Dynamics of the Photo-Perturbed Correlated Electron System 1T-TaS2

Isabella Avigo,Kai Rossnagel,Matthias Kalläne,Uwe Bovensiepen,Ping Zhou,Manuel Ligges

doi:10.3390/app9010044

Isabella Avigo, Kai Rossnagel + Show 4 more

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https://doi.org/10.3390/app9010044

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Journal: Applied Sciences	Publication Date: Dec 24, 2018
Citations: 10	License type: CC BY 4.0

Affiliation: Kiel University, University of Duisburg-Essen

Abstract

We investigate the perturbation and subsequent recovery of the correlated electronic ground state of the Mott insulator 1T-TaS 2 by means of femtosecond time-resolved photoemission spectroscopy in normal emission geometry. Upon an increase of near-infrared excitation strength, a considerable collapse of the occupied Hubbard band is observed, which reflects a quench of short-range correlations. It is furthermore found that these excitations are directly linked to the lifting of the periodic lattice distortion which provides the localization centers for the formation of the insulating Mott state. We discuss the observed dynamics in a localized real-space picture.

Highlights

Correlated electron systems play an important role in modern condensed matter physics, as they emerge in the context of e.g., high-temperature superconductivity [1] or metal-to-insulator transitions [2]
We discuss (i) the dynamics of a sudden quench of charge order, caused by femtosecond laser excitation, (ii) the subsequent recovery and (iii) the role of electron-phonon coupling in a Mott insulator that exhibits simultaneously strong electron-electron and electron-phonon interaction
The obtained surfaces were excited with 50 fs laser pulses from a commercial regenerative Ti:Sa laser amplifier (Coherent RegA 9040, hω1 =1.55 eV) and subsequently probed by direct photoemission using UV pulses, which were generated by two consecutive frequency-doubling processes of the fundamental pulses using β-barium borate crystals

Summary

Introduction

Correlated electron systems play an important role in modern condensed matter physics, as they emerge in the context of e.g., high-temperature superconductivity [1] or metal-to-insulator transitions [2]. Corresponding experiments in the time domain have been performed e.g., by investigating the re-emergence of charge order from a quenched disorder, induced by photo-perturbation, on the organic Mott insulator ET-F2 TCNQ, a system that only exhibits negligible electron-phonon interaction and, can be well described by means of pure electronic models [4,5] These dynamics might become more complex when the general case is addressed, namely, the investigation of systems where coupling to other degrees of freedom play an important role [6,7,8] and/or different types of order compete or coexist. In its high-temperature state, the system is metallic and can be characterized by a hexagonal arrangement of atoms within the Ta planes of the S-Ta-S building layers (Figure 1a)

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Discussion

Conclusion