Control of Competing Superconductivity and Charge Order By Non-equilibrium Currents

Strongly correlated materials often have rich phase diagrams. However, in many cases potentially interesting states are suppressed by competing phases which are thermodynamically in close proximity, e.g. superconductivity (SC) and charge-density-wave (CDW) order. How to control and distinguish competing phases arises as a very interesting and relevant question which is currently under intense research. In this work we study the competing CDW and SC order in the attractive Hubbard model under a voltage bias, using non–equilibrium steady-state (NESS) dynamical mean-field theory. We show that the CDW is suppressed in a current-carrying NESS by an effect beyond a simple Joule-heating mechanism. A “supercooled” metallic state is stabilized at a NE temperature lower than the equilibrium SC T_c. Since a current-carrying SC state is dissipation-less and thus not subject to the same non-thermal suppression, it can nucleate out of the supercooled metal. Hence, an electric current can change the relative stability of different phases compared to thermal equilibrium, even when a system appears locally thermal due to electron-electron scattering. This provides a general perspective to control intertwined orders out of equilibrium.
[arXiv:1804.09608]