SPICE Workshop on Quantum materials and quantum information science May 19th - 21st, 2026
Julian Ingham
Transition metal dichalcogenides MX₂ (TMDs) are atomically thin materials with a variety of fascinating properties depending on their structure, or polytype -- the 1H polytype is a semiconductor, the 1T is a semimetal, and 1T' is a topological insulator. In this talk I will discuss how quantum geometry determines the properties of TMDs in three ways. First, I will discuss recent STM results which reveal that 1H-TMDs are described by a topological phase known as an obstructed atomic limit: by mapping how the charge density evolves with bias voltage, we show that the underlying Wannier orbital which makes up the valence band is forced to lie in an empty position of the lattice, where no atoms are present. Second, I will discuss a new model of monolayer TMDs which is simultaneously capable of describing the bandstructure of the 1H, 1T, and 1T' polytype. Interestingly, the model is equivalent to a breathing kagome lattice with emergent non symmorphic symmetries in the 1H case; the bandstructure of the other polytypes is obtained by distorting the model in different ways. Thirdly, I will discuss how the multiorbital model sheds light on moiré TMDs, demonstrating that the interlayer tunneling in twisted bilayers is dominated by interorbital tunnelling processes.