Emergent surface resonance from charge density wave symmetry breaking in TiSe2

TL;DR

This study reveals a surface resonant state in TiSe2 caused by charge density wave symmetry breaking, with potential for engineering quantum states in layered materials.

Contribution

It demonstrates the emergence of a surface resonant state in TiSe2 due to CDW symmetry breaking, supported by experimental and theoretical evidence.

Findings

Surface resonant state appears within the CDW spectrum.

Spectral weight collapses around 160 K, below the CDW transition.

Slab DFT+U calculations confirm a surface localized resonance.

Abstract

Surface confined electronic states provide a fertile ground for discovering emergent phenomena that have no counterpart in the bulk, offering new routes to manipulate correlations, symmetry breaking, and dimensionality at the atomic scale. Here, we show that charge density wave (CDW) symmetry breaking can yield a surface states in 1T-TiSe2. Micro angle resolved photoemission spectroscopy resolves a sharp, two dimensional surface resonant state (SRS) that emerges within the CDW reconstructed low energy spectrum. The SRS exhibits notable temperature dependence and its spectral weight collapses around 160 K, while CDW transition temperature TCDW is commonly reported as 202 K. Slab DFT+U calculations reproduce a surface localized resonance when CDW folding brings valence and conduction states into near degeneracy, suggesting a correlation tuned, surface selective origin. These results point to a form of correlation-tuned surface resonance in a layered CDW compound and suggest a framework for engineering low dimensional quantum states in van der Waals materials via symmetry breaking and electronic structure tuning.