Real-time quantum Monte Carlo for the spin-boson model

Olga Goulko, Guy Cohen, Moshe Goldstein +1 more

Reinhold Egger, U. Weiss

Arnim Lück, Manfred Winterstetter, Ulrich Weiß +1 more

A discretized path integral formulation of the real-time dynamics applicable to a general external field is derived for the driven spin-boson model to extend the recently developed real-time Quantum Monte Carlo algorithm to driven systems. Numerical results are obtained for a monochromatic periodic driving force and Ohmic dissipation with a high-frequency cutoff. The impact of an external driving field on the dissipative dynamics is examined for systems with a time-dependent bias as well as a time-dependent interstate coupling matrix element. This method is easily generalized to multistate tight-binding models.

Mark R. Dowling, Matthew J. Davis, P. D. Drummond +1 more

Markus Keil, Herbert Schoeller

Using a real-time renormalization-group method we determine the complete dynamics of the spin-boson model with Ohmic dissipation for coupling strengths $\ensuremath{\alpha}\ensuremath{\lesssim}0.1--0.2.$ We calculate the relaxation and dephasing time, static susceptibility, and correlation functions. Our results are consistent with quantum Monte Carlo simulations and the Shiba relation. We present reliable results for finite cutoff and finite bias in a regime where perturbation theory in $\ensuremath{\alpha}$ or in tunneling breaks down. Furthermore, an unambiguous comparison to results from the Kondo model is achieved.

Chi H. Mak, David Chandler

A method of solving the sign problem in the Monte Carlo path-integral simulations of quantum dynamics is presented. Our method is based on the distortion of integration contours in conjunction with a stationary-phase-filtering method. Using this importance sampling, correlation functions for the spin-boson model have been computed for real times much longer than \ensuremath{\beta}\ensuremath{\Elzxh}.