Condensed Matter/Materials & Biological Physics Seminar with Vikram Deshpande on Mechanical Perturbation of Topological Materials

The field of topological materials has burgeoned of late due to its implications for areas such as dissipationless electronics and decoherence-free quantum computing, among others. Of the many topological materials under study, twisted bilayer graphene (TBG) and magnetic topological insulators (MTI) have attracted attention because they host multiple ground states in the same sample such as magnetism, superconductivity, Chern insulator, axion insulator, etc. While their electronic properties have been well-explored in the last few years, much less is known about how these properties couple to the lattice. In my lab, we have developed techniques to deform these materials controllably and study their resulting electronic properties in-situ. In the complementary experiment, we sense the electronic ground state through the mechanical degree of freedom. I will present recent results from our group applying these two techniques to the case of twisted bilayer graphene and the intrinsic magnetic topological insulator MnBi2Te4, respectively. We are able to tune the Hofstadter’s spectrum of non-magic
angle TBG and induce magnetism in non-magnetic correlated insulating states of magic-angle TBG using strain, for example, and detect various magnetic states and measure magnetoelastic couplings in the case of MTIs. Our advances present unique routes to tuning and sensing the parameter space of these exciting materials.