Hybrid NRG-DMRG approach to real-time dynamics of quantum impurity systems

TL;DR

This paper introduces a hybrid NRG-DMRG method to accurately simulate the real-time dynamics of quantum impurity systems over long timescales, combining low-energy Hamiltonian generation with adaptive DMRG techniques.

Contribution

The authors develop a hybrid approach that leverages NRG to generate low-energy Hamiltonians, enabling long-time real-time dynamics simulations with DMRG, and validate it against analytical predictions.

Findings

Decay time of oscillations diverges quadratically with interaction strength U

Method achieves accurate long-time dynamics simulations

Excellent agreement with analytical 1/U expansion predictions

Abstract

A hybrid approach to nonequilibrium dynamics of quantum impurity systems is presented. The numerical renormalization group serves as a means to generate a suitable low-energy Hamiltonian, allowing for an accurate evaluation of the real-time dynamics of the problem up to exponentially long times using primarily the time-adaptive density-matrix renormalization group. We extract the decay time of the interaction-enhanced oscillations in the interacting resonant-level model and show their quadratic divergence with the interaction strength U. Our numerical analysis is in excellent agreement with analytic predictions based on an expansion in 1/U.