Details regarding talk given by alumnus

IISc UG alumnus Archisman Panigrahi(2017-2022), presently pursuing Physics Phd at MIT, would be delivering a talk at Physics Department tomorrow. The talk would be would be accessible to anyone who took an introductory condensed matter course(CMP1/SSP). Please find the details below.

Title : Transport signatures of electronic ordering in graphene flat bands Date : 15.01.2024 Time : 4.00 PM Venue : Lecture Hall-04 (F0-11)

Abstract : In the nearly dispersionless bands of flat-band graphene, the electronic interactions play a significant role at low temperature, where exchange interactions favor valley-polarized, spin-polarized and momentum-polarized orders via a generalized Stoner mechanism. These ordered phases spontaneously break parity and time-reversal symmetries, and undergo a continuous phase transition into the corresponding disordered phase as the temperature is increased. Since the ordering involves orbital degrees of freedom of the charge carriers, it is expected to impact resistivity in a way which is uniquely sensitive to the ordering type. Here we explore this physics, focusing on the momentum-polarized orders, and predict a unique signature of ordering—the negative temperature dependence of resistivity at the order-disorder transition. Namely, rising temperatures, despite increasing electronic disorder, drive the system into a more conducting state. This counterintuitive behavior originates from an interplay between exchange interactions that make carriers aggregate in Fermi pockets and thermal activation that excites carriers out of the Fermi pockets. We argue that this behavior remains robust in the presence of electron-phonon scattering and is therefore expected to be generic. I request you to join this insightful discussion!