Physics (Internal)

Rotating Kekulé mass in graphene: a 'hydrogen atom' for non-equilibrium quantum systems

This event is part of the Condensed Matter Theory Seminar Series.

Abstract: Driven condensed matter systems are emerging as subjects of great theoretical and experimental interest due to the possibility of using external driving to engineer novel properties in materials. Nevertheless, such systems consistently pose substantial challenges to theoretical understanding; their statistical mechanics lacks intuitive basic principles, even at zero temperature, and their thermodynamic behavior is generally quite complicated. In this talk, we present a case study of the rotating Kekulé mass in graphene [PRL 110, 176603 (2013)], which provides a setting where these concerns can be studied in detail. The rotating mass, which is generated by driving an optical phonon mode, modifies substantially the properties of un-driven graphene. For instance the rotating Kekulé mass may provide an experimentally feasible route to generating tunable band gaps in graphene. Furthermore, it generates topologically protected pumping phenomena, which include the transport of fractional charge around the edges of a finite sample. Finally, the thermodynamics of the system admits a remarkably simple description in terms of a "generalized energy," which allows us to recover an intuitive understanding of the system based on equilibrium statistical mechanics.