Carrier-Density Control of the Quantum-Confined 1$T$-TiSe$_2$ Charge-Density-Wave

TL;DR

This study demonstrates how potassium adsorption on 1T-TiSe2 can create and tune a two-dimensional electron gas, controlling exciton condensation and quantum confinement in the charge-density-wave phase.

Contribution

It introduces a method to control exciton-related quantum states in 1T-TiSe2 via alkali-metal dosing, combining experimental and theoretical approaches.

Findings

Potassium induces a 2DEG and quantum confinement at the surface.

Carrier density tuning nullifies exciton condensation energy gain.

Long-range structural order is preserved despite electronic changes.

Abstract

Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schr\"odinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of 1$T$-TiSe$_2$ induce the creation of a two-dimensional electron gas (2DEG) and quantum confinement of its charge-density-wave (CDW) at the surface. By further changing the K coverage, we tune the carrier-density within the 2DEG that allows us to nullify, at the surface, the electronic energy gain due to exciton condensation in the CDW phase while preserving a long-range structural order. Our study constitutes a prime example of a controlled exciton-related many-body quantum state in reduced dimensionality by alkali-metal dosing.