FRIEDEL OSCILLATIONS IN NANOWIRES AT FINITE BIAS VOLTAGE

We investigate the charge density oscillations in a nanowire coupled asymmetrically to two leads. Depending on this asymmetry, the Friedel oscillations can either be characterized by a single wave-vector or become a superposition of oscillations with different wave-vectors. Using the formalism of nonequilibrium Keldysh Green functions, we derive a simple equation that determines bias voltage dependence of the wave-length of the oscillations. Finally, we discuss limitations of the commonly used formula that describes the spatial character of the Friedel oscillations.