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Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 59: Complex Oxides Interfaces and Charge Order

TT 59.8: Vortrag

Donnerstag, 4. April 2019, 17:00–17:15, H22

Scanning tunneling microscopy on an excitonic insulator Ta2NiSe5Qingyu He1, Xinglu Que1, Alexander Yaresko1, •Andreas Rost1, Masahiko Isobe1, Tomohiro Takayama1, Lihui Zhou1, and Hidenori Takagi1,21Max Planck Institute for solid state research, Stuttgart, Germany — 2University of Tokyo, Tokyo, Japan

Ta2NiSe5 is the strongest candidate for the long conjectured excitonic insulator state. It is a direct zero gap semiconductor at high temperature, and undergoes at Tc = 326 K a semiconductor-insulator transition simultaneous with an orthorhombic-monoclinic q = 0 structure transition. Our low temperature STM evidences its layered structure with rippling atomic chains. The local spectroscopy reveals the opening of the excitonic insulator gap and the spectral weight shift with decreasing temperature. High resolution STM topography shows a local distortion associated with the structure transition. This distortion may play an important role in the formation of the excitonic state, as also supported by our band structure calculations.

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