1202.0196 (Sergey Smirnov et al.)

Spin channel Keldysh field theory for interacting quantum dots    [PDF]

Sergey Smirnov, Milena Grifoni

We develop a low-energy nonequilibrium field theory for interacting quantum
dots. The theory is based on the Keldysh field integral in the spin channel of
the quantum dot described by the single impurity Anderson Hamiltonian. The
effective Keldysh action is a functional of the Hubbard-Stratonovich
magnetization field decoupling the quantum dot spin channel. We investigate
which kind of physics is described by this action when it is expanded up to the
second order with respect to the magnetization field. It is shown that this
simple quadratic spin channel field theory describes nonequilibrium interacting
quantum dots at low temperatures and weak electron-electron interactions, up to
the contacts-dot coupling energy. Besides its simplicity, an additional
advantage of the theory is that it correctly describes the unitary limit giving
the correct result for the conductance maximum in the Kondo regime. Thus our
theory establishes a simple basis relevant for future more elaborate spin
channel field integral theories for the Kondo effect in nonequilibrium
nanodevices.

View original: http://arxiv.org/abs/1202.0196