Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 73: Correlated Electrons: Nonequilibrium Quantum Many-Body Systems 2
TT 73.8: Vortrag
Donnerstag, 23. März 2017, 17:00–17:15, HSZ 304
Coherent Order Parameter Oscillations in the Ground State of the Excitonic Insulator Ta2NiSe5 — •Daniel Werdehausen1,2, Tomohiro Takayama1,2, Marc Höppner1, Gelon Albrecht1,2, Andreas W. Rost1,2, Yangfan Lu3, Dirk Manske1, Hidenori Takagi1,2, and Stefan Kaiser1,2 — 1Max Planck Institut für Festkörperforschung, Stuttgart, Germany — 2Universität Stuttgart, Germany — 3University of Tokyo, Japan
The excitonic insulator state is an intriguing correlated electron phase that consists of condensed excitons. However, its experimental identification has proven to be challenging, mainly because it is difficult to probe the coherence of a condensate directly. One possibility is the observation of a condensate’s intrinsic collective modes, which are equivalent to the Higgs- and Goldstone modes in superconductors. Here we report strong evidence for the existence of an excitonic insulator state in Ta2NiSe5: Using non-linear excitations with short laser pulses we identify a phonon-coupled state of the exciton condensate, in which its electronic Higgs-mode couples to a low frequency phonon [1]. The Higgs-mode contribution substantiates the picture of an electronically driven phase transition and can be used to characterize the transient order parameter of the excitonic insulator as a function of temperature and excitation density.
[1] D. Werdehausen et al. arxiv:1611.01053 (2016).