arXiv subjects

Zurab Ratiani

Publications and source records attributed to Zurab Ratiani.

3 recordsLinked to original sources

arXiv2010

Nonequilibrium dynamics in a two-channel Kondo system due to a quantum quench

Recent experiments by Potok et al. have demonstrated a remarkable tunability between a single-channel Fermi liquid fixed point and a two-channel non-Fermi liquid fixed point. Motivated by this we study the nonequilibrium dynamics due to a sudden quench of the parameters of a Hamiltonian from a single-channel to a two-channel anisotropic Kondo system. We find a distinct difference between the long time behavior of local quantities related to the impurity spin as compared to that of bulk quantities related to the total (conduction electrons + impurity) spin of the system. In particular, the local impurity spin and the local spin susceptibility are found to equilibrate, but in a very slow power-law fashion which is peculiar to the non-Fermi liquid properties of the Hamiltonian. In contrast, we find a lack of equilibration in the two particle expectation values related to the total spin of the system.

cond-mat.str-el↗

arXiv2009

1/N expansion of the nonequilibrium infinite-U Anderson Model

Results are presented for the nonequilibrium infinite-U Anderson model using a large-N approach, where $N$ is the degeneracy of the impurity level, and where nonequilibrium is established by coupling the level to two leads at two different chemical potentials so that there is current flow. A slave-boson representation combined with Keldysh functional integral methods is employed. Expressions for the static spin susceptibility $χ_S$ and the conductance $G$ are presented to ${\cal O}(\frac{1}{N})$ and for an applied voltage difference $V$ less than the Kondo temperature. The correlation function for the slave-boson is found to be significantly modified from its equilibrium form in that it acquires a rapid decay in time with a rate that equals the current induced decoherence rate. Physical observables are found to have a rather complex dependence on the coupling strength to the two leads which can lead to asymmetric behavior $χ_S(V) \neq χ_S(-V)$, $G(V)\neq G(-V)$ both in the mixed valence and in the Kondo regime.

cond-mat.str-el↗

arXiv2005

The conformally invariant vector field on $R \times S^3$

In this diploma thesis vector field is constructed on $R \times S^3$. The free lagrangian on the curved space is invariant under conformal transformations of the dynamical field $A_m(x)$. The gauge fixing term is not conformally invariant, but it is invariant under Poincare transformations of the fields $A_m(x)$. Propagator quantisation is carried out. The energy spectrum of the physical subspace is analogous to the spectrum of flat quantum field theory.

hep-th↗