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arXiv · 2104.07032

Failed excitonic quantum phase transition in Ta$_2$Ni(Se$_{1-x}$S$_x$)$_5$

Pavel A. Volkov·Mai Ye·Himanshu Lohani·Irena Feldman·Amit Kanigel·Girsh Blumberg
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Abstract

We study the electronic phase diagram of the excitonic insulator candidates Ta$_2$Ni(Se$_{1-x}$S$_x$)$_5$ [x=0, ... ,1] using Raman spectroscopy. Critical excitonic fluctuations are observed, that diminish with $x$ and ultimately shift to high energies, characteristic of a quantum phase transition. Nonetheless, a symmetry-breaking transition at finite temperatures is detected for all $x$, exposing a cooperating lattice instability that takes over for large $x$. Our study reveals a failed excitonic quantum phase transition, masked by a preemptive structural order.

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Pavel A. Volkov, Mai Ye, Himanshu Lohani, Irena Feldman, Amit Kanigel, Girsh Blumberg. 2021-04-14. Failed excitonic quantum phase transition in Ta$_2$Ni(Se$_{1-x}$S$_x$)$_5$. https://doi.org/10.1103/physrevb.104.l241103

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