Controlling the Charge Density Wave Transition in Single-Layer TiTe<sub>2<i>x</i></sub>Se<sub>2(1-<i>x</i>)</sub> Alloys by Band Gap Engineering.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38117702.
- Also identified by DOI 10.1021/acs.nanolett.3c03776 and PMC identifier 10786161.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Closing the band gap of a semiconductor into a semimetallic state gives a powerful potential route to tune the electronic energy gains that drive collective phases like charge density waves (CDWs) and excitonic insulator states. We explore this approach for the controversial CDW material monolayer (ML) TiSe<sub>2</sub> by engineering its narrow band gap to the semimetallic limit of ML-TiTe<sub>2</sub>. Using molecular beam epitaxy, we demonstrate the growth of ML-TiTe<sub>2<i>x</i></sub>Se<sub>2(1-<i>x</i>)</sub> alloys across the entire compositional range and unveil how the (2 × 2) CDW instability evolves through the normal state semiconductor-semimetal transition via <i>in situ</i> angle-resolved photoemission spectroscopy. Through model electronic structure calculations, we identify how this tunes the relative strength of excitonic and Peierls-like coupling, demonstrating band gap engineering as a powerful method for controlling the microscopic mechanisms underpinning the formation of collective states in two-dimensional materials.