Steady-State Density Functional Theory for quantum transport and spectral functions*

Steady-State Density Functional Theory (i-DFT) is a formalism to describe open quantum systems in nonequilibrium steady states. i-DFT is based on the one-to-one correspondence between the pair density and steady current and the pair local potential and applied voltage. The resulting Kohn-Sham system features two exchange-correlation (xc) potentials, a local xc potential and an xc contribution to the voltage. After revisiting the fundamentals of i-DFT we apply the formalism to strongly correlated quantum dots at finite current and temperature. We show that the well-known discontinuity of the DFT xc potential at integer particle number bifurcates as the current starts flowing. We also show that the i-DFT formalism can be used to calculate the quantum system spectral function, a relevant quantity in photoemission spectroscopy.