New Phase Transitions in Atomically Thin Quantum Materials

We have recently demonstrated an experimental platform to isolate 2D quantum materials that are unstable in the ambient environment. I will discuss our studies of the charge density wave (CDW) compound 1T-TaS₂ and Weyl semimetal 1T’-MoTe₂ in the atomically thin limit, made possible using this technique. In TaS₂, we

1) find that the lock-in CDW transition becomes increasingly metastable in thin samples,
2) demonstrate electrical control over this transition,
3) spatially image the growth of CDW domains, and
4) uncover a new surface CDW transition distinct from that in the bulk layers.

In MoTe₂, lowering dimensionality suppresses the intermediate centrosymmetric phase, driving the Weyl ground state up to and beyond room temperature. The changing electronic structure of thin samples are studied by magnetotransport at low temperature.