Out-of-equilibrium dynamics in a quantum impurity model: numerics for particle transport and entanglement entropy

TL;DR

This paper studies the out-of-equilibrium behavior of a quantum impurity model, analyzing current-voltage characteristics, entanglement entropy growth, and spatial entropy profiles using numerical simulations, revealing how these properties depend on interaction strength.

Contribution

It extends previous results on current-voltage curves in the IRLM and provides new numerical estimates of the Kondo scale and entanglement entropy growth in out-of-equilibrium conditions.

Findings

Current-voltage curves are characterized for various interaction strengths.

The entropy rate scales with the Kondo temperature and interaction.

Spatial entropy profiles exhibit specific structural features.

Abstract

We investigate the out-of-equilibrium properties of a simple quantum impurity model, the interacting resonant level model (IRLM). We focus on the scaling regime, where the bandwidth of the fermions in the leads is larger than all the other energies, so that the lattice and the continuum versions of the model become equivalent. Using time-dependent DMRG simulations initialized with states having different densities in the two leads we extend the results of Boulat, Saleur and Schmitteckert [Phys. Rev. Lett. 101, 140601 (2008)] concerning the current-voltage ($I$-$V$) curves, for several values of the interaction strength $U$. We estimate numerically the Kondo scale $T_B$ and the exponent $b(U)$ associated to the tunneling of the fermions from the leads to the dot. Next we analyze the quantum entanglement properties of the steady states. We focus in particular on the entropy rate $\alpha$, describing the linear growth with time of the bipartite entanglement in the system. We show that, as for the current, $\alpha/T_B$ is described by some function of $U$ and of the rescaled bias $V/T_B$. Finally, the spatial structure of the entropy profiles is discussed.