1304.1965 (B. Zenker et al.)

Chiral charge order in 1$T$-TiSe$_2$: importance of lattice degrees of
freedom    [PDF]

B. Zenker, H. Fehske, H. Beck, C. Monney, A. R. Bishop

We deal with the recently discovered chiral property of the charge-density-wave (CDW) phase in 1$T$-TiSe$_2$. Chirality has not been detected in CDW systems before and a microscopic description lacks so far. In this work we argue that the lattice degrees of freedom are crucial for this novel phenomena. We motivate a theoretical model that shows a CDW at low temperature, which is accompanied by a periodic lattice distortion, as it is the case in 1$T$-TiSe$_2$. Furthermore, an explicit phonon-phonon interaction must be taken into account to achieve a stable chiral CDW. Within this model we analyze the competition between the electron-electron interaction and the electron-phonon coupling with view on the electron-hole pairing. We present the ground-state phase diagram and estimate the interaction constants for 1$T$-TiSe$_2$. Our results suggest a combined scenario of a band-type Jahn-Teller effect and an excitonic insulator to drive the CDW transition in this material.

View original: http://arxiv.org/abs/1304.1965