Title:  Super current diode effect and finite momentum superconductivity

Speaker: Fan Qi (Noah) Yuan

Time:  September 10（Friday）, 10:00 am

Place:  Rm M830, IOP-CAS

Abstract:

  When both inversion and time-reversal symmetries are broken, the critical current of a superconductor can be nonreciprocal. In this talk we show that in certain classes of two-dimensional superconductors with antisymmetric spin-orbit coupling, Cooper pairs acquire a finite momentum upon the application of an in-plane magnetic field, and as a result, critical currents in the direction parallel and antiparallel to the Cooper pair momentum become unequal. This supercurrent diode effect is also manifested in the polarity-dependence of in-plane critical fields induced by a supercurrent. These nonreciprocal effects may be found in polar SrTiO$_3$ film, few-layer MoTe$_2$ in the $T_d$ phase, and twisted bilayer graphene in which the valley degrees of freedom plays the role analogous to spin.