R. Egger

Low-temperature dynamical simulation of spin-boson systems

The dynamics of spin-boson systems at very low temperatures has been studied using a real-time path-integral simulation technique, which combines a stochastic Monte Carlo sampling over the quantum fluctuations with an exact treatment of the quasiclassical degrees of freedom. To a large degree, this special technique circumvents the dynamical sign problem and allows the dynamics to be studied directly up to long real times in a numerically exact manner. This method has been applied to two important problems: (1) crossover from nonadiabatic to adiabatic behavior in electron-transfer reactions, (2) the zero-temperature dynamics in the antiferromagnetic Kondo region 1/2K1, where K is Kondos parameter.

Crossover from Fermi Liquid to Wigner Molecule Behavior in Quantum Dots

The crossover from weak to strong correlations in parabolic quantum dots at zero magnetic field is studied by numerically exact path-integral Monte Carlo simulations for up to eight electrons. By the use of a multilevel blocking algorithm, the simulations are carried out free of the fermion sign problem. We obtain a universal crossover governed only by the density parameter

Quantum rates for nonadiabatic electron transfer

{r}_{s}

A multilevel blocking approach to the sign problem in real-time quantum Monte Carlo simulations

. For

Path-integral Monte Carlo simulations without the sign problem: multilevel blocking approach for effective actions

{r}_{s}g{r}_{c}

Dynamical effects in the calculation of quantum rates for electron transfer reactions

, the data are consistent with a Wigner molecule description, while, for

MULTILEVEL BLOCKING APPROACH TO THE FERMION SIGN PROBLEM IN PATH-INTEGRAL MONTE CARLO SIMULATIONS

{r}_{s}l{r}_{c}

Conductance quantization and snake states in graphene magnetic waveguides

, Fermi liquid behavior is recovered. The crossover value

Electric-dipole-induced universality for Dirac fermions in graphene.

{r}_{c}\ensuremath{\approx}4

Landau levels, edge states, and strained magnetic waveguides in graphene monolayers with enhanced spin-orbit interaction

is surprisingly small.