|
Non-equilibrium quantum phase transitions have so far received only limited
attention despite the strong ongoing interest in classical
out-of-equilibrium phase transitions. This is in part due to the
fact, that dynamics and statics are already
intimitely linked at an equilibrium quantum phase transition and because
bulk out-of-equilibrium systems are difficult to characterize.
For this reason, nanostructured devices constitute
ideal systems both theoretically and experimentally, to study
well defined out-of-equilibrium states that give raise to unique
steady-state limits.
We recently showed, that such a system, a
magnetic single-electron transistor, can be tuned
through a continuous quantum phase transition as the applied gate voltage
is tuned [1,2]. To address the non-linear electronic transport near the
transistion, we generalized the system to a large-N limit,
where vertex corrections to the quantum Boltzmann equation vanish and our
treatment becomes exact.
We determine the universal scaling functions for the I-V characteristics
in the linear and non-linear regime of the long-time limit and analyze the (generalized) fluctuation dissipation relation across the phase diagram.
[1] S. Kirchner, L. Zhu, Q. Si and D. Natelson, Proc.Natl.Acad.Sci. USA 102 (2005) 18824 [2] S. Kirchner, Q. Si, Physica B, volume 403, issues 5-9 p. 1199 (2008). |
|