CM Seminar: "Dimensional reduction and other commensurability phenomena in moiré systems" (Nisarga Paul, MIT)

  • Starts: 3:30 pm on Wednesday, December 6, 2023
  • Ends: 4:30 pm on Wednesday, December 6, 2023
Moiré materials, such as twisted bilayer graphene or transition metal dichalcogenides, have revealed a wealth of new and unexpected strongly correlated quantum effects. This is due, in large part, to the new regimes accessible by having a lattice constant (i.e. the moiré period) orders of magnitude greater than that of natural solids. Both the moiré period and the magnetic length at accessible magnetic fields are O(10) nanometers, and this simple observation suggests that moiré systems are in a new regime where commensurability phenomena can have observable consequences. We detail some of these commensurability phenomena, highlighting an effect in the presence of infinitesimal strain which results in electrons directionally localized along a direction which switches with field. This “dimensional reduction” can be understood as localization-delocalization transitions being driven in effective Aubry-André-like 1D models which capture the 2D physics, or in a complementary manner from a semiclassical network model. If time permits we will draw connections to recently observed fractional quantum anomalous Hall effects and discuss the possibility of observing commensurability phenomena at zero field due to interactions alone. Based on work done with Philip J.D. Crowley and Liang Fu.
Location:
SCI 352
Speaker
Nisarga Paul
Institution
MIT
Host
Alexey Khudorozhkov