Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 42: Charge Order

TT 42.9: Talk

Tuesday, March 13, 2018, 12:30–12:45, HFT-FT 131

The Coherent Response in the Ground State of the Excitonic Insulator Ta₂NiSe₅ — •Minjae Kim^1,2, Parmida Shabestari^1,2, Emily Huang^1,2, Daniel Werdehausen^1,2, Steinn Ymir Agustsson^1,2, Timofei Larkin¹, Alexander Boris¹, Tomohiro Takayama^1,2, Hao Chu^1,2, Hidenori Takagi^1,2, and Stefan Kaiser^1,2 — ¹Max Planck Institute for Solid State Research, Stuttgart, Germany — ²University of Stuttgart, Germany

The excitonic insulator (EI) is an intriguing phase of condensed excitons undergoing a BEC-type transition. A prominent candidate has been identified in Ta₂NiSe₅ [1]. Ultrafast spectroscopy allows tracing the coherent response of the EI condensate directly in the time domain. Probing the collective electronic response we can identify the Higgs-amplitude mode of the condensate. In addition we find a peculiar coupling of the EI phase to a low frequency phonon mode [2]. We will discuss the transient response on multiple energies scales ranging from the exciton dynamics in the NIR down to the coherent THz response of the gap.
Y.F. Lu et al., Nat. Comm. 8, 14408 (2017).
D. Werdehausen et al., arXiv:1611.01053 (2016).