Carrier-Density Control of the Quantum-Confined 1T-TiSe_{2} Charge Density Wave.

Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schrödinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of 1T-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 Letter constitutes a prime example of a controlled exciton-related many-body quantum state in reduced dimensionality by alkali-metal dosing.