English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We investigate the microscopic mechanisms of the charge-density-wave (CDW)formation in a monolayer TiSe$_2$ using a realistic multiorbital $d$-$p$ modelwith electron-phonon coupling and intersite Coulomb (excitonic) interactions.First, we estimate the tight-binding bands of Ti $3d$ and Se $4p$ orbitals inthe monolayer TiSe$_2$ on the basis of the first-principles band structurecalculations. We thereby show orbital textures of the undistorted bandstructure near the Fermi level. Next, we derive the electron-phonon couplingusing the tight-binding approximation and show that the softening occurs in thetransverse phonon mode at the M point of the Brillouin zone. The stability ofthe triple-$q$ CDW state is thus examined to show that the transverse phononmodes at the M$_1$, M$_2$, and M$_3$ points are frozen simultaneously. Then, weintroduce the intersite Coulomb interactions between the nearest-neighbor Tiand Se atoms that lead to the excitonic instability between the valence Se $4p$and conduction Ti $3d$ bands. Treating the intersite Coulomb interactions inthe mean-field approximation, we show that the electron-phonon and excitonicinteractions cooperatively stabilize the triple-$q$ CDW state in TiSe$_2$. Wealso calculate a single-particle spectrum in the CDW state and reproduce theband folding spectra observed in photoemission spectroscopies. Finally, toclarify the nature of the CDW state, we examine the electronic charge densitydistribution and show that the CDW state in TiSe$_2$ is of a bond-type andinduces a vortex-like antiferroelectric polarization in the kagome network ofTi atoms.

Exciton-phonon cooperative mechanism of the triple-$q$ charge-density-wave and antiferroelectric electron polarization in TiSe$_2$