Pedro Ribeiro
CeFEMA e Departamento de Física, IST, ULisboa

Abstract: Spin- and charge density waves are a common phenomenon in condensed matter physics. Charge density waves were predicted by R. Peierls who showed that a one-dimensional lattice can become unstable and undergo a  transition due to the electron-phonon coupling. This Peierls transition has been well studied and can be conveniently described within a path integral representation. Much less, however, is known about its fate  away from thermal equilibrium. In this talk, we address the fate of this instability under non-equilibrium conditions created by imposing a finite voltage across the system. We will give a brief introduction into  non-equilibrium Green’s functions using the path integral on the Keldysh contour. Then, using this technique, we establish that the finite voltage drop across the system changes the ordering wave function away from its equilibrium position at $2k_F$. The amount of this shift  depends on the applied voltage and on the properties of the contacts. Finally, we discuss the nature of the non-equilibrium steady-state obtained at zero temperature in the incommensurate case.