In: Physical Review B, 2013, vol. 88, no. 16, p. 165115
We discuss the general formalism and validity of weak-coupling perturbation theory as an impurity solver for nonequilibrium dynamical mean-field theory. The method is implemented and tested in the Hubbard model, using expansions up to fourth order for the paramagnetic phase at half filling and third order for the antiferromagnetic and paramagnetic phase away from half filling. We explore various...
|
In: Physical Review B, 2013, vol. 88, no. 7, p. 075135
We extend the nonequilibrium dynamical mean field (DMFT) formalism to inhomogeneous systems by adapting the “real-space” DMFT method to Keldysh Green's functions. Solving the coupled impurity problems using strong-coupling perturbation theory, we apply the formalism to homogeneous and inhomogeneous layered systems with strong local interactions and up to 39 layers. We study the diffusion of...
|
In: EPL (Europhysics Letters), 2013, vol. 102, no. 3, p. 37011
We use different numerical approaches to calculate the double occupancy and magnetic susceptibility as a function of a bias voltage in an Anderson impurity model. Specifically, we compare results from the Matsubara voltage quantum Monte Carlo approach (MV-QMC), the scattering states numerical renormalization group (SNRG), and real-time quantum Monte Carlo (RT-QMC), covering Coulomb repulsions...
|
In: Journal of Physics: Conference Series, 2013, vol. 427, no. 1, p. 012005
Using dynamical mean-field theory and the non-crossing approximation as impurity solver, we study the response of a Mott insulator to strong dc electric fields. The breakdown of the Mott insulating state is triggered by field-induced creation of doublon-hole pairs. In a previous investigation, Ref. [1], it was found that the system approaches a long-lived quasi-steady state in which the current...
|
In: Physical Review B, 2013, vol. 87, no. 12, p. 125149
We describe a recent implementation of the combined GW and dynamical mean field method (GW+DMFT) for the two-dimensional Hubbard model with onsite and nearest-neighbor repulsion. We clarify the relation of the GW+DMFT scheme to alternative approaches in the literature, and discuss the corresponding approximations to the free-energy functional of the model. Furthermore, we describe a numerically...
|
In: Physical Review Letters, 2013, vol. 110, no. 13, p. 136404
We study dynamical phase transitions from antiferromagnetic to paramagnetic states driven by an interaction quench in the fermionic Hubbard model using the nonequilibrium dynamical mean-field theory. We identify two dynamical transition points where the relaxation behavior qualitatively changes: one corresponds to the thermal phase transition at which the order parameter decays critically slowly...
|
In: Physical Review Letters, 2013, vol. 110, no. 16, p. 167002
Using angle-resolved photoemission spectroscopy, we study the evolution of the number of carriers in Ba(Fe₁₋Cox)₂As₂ as a function of Co content and temperature. We show that there is a k-dependent energy shift compared to density functional calculations, which is large below 100 K at low Co contents and reduces the volume of hole and electron pockets by a factor 2. This k...
|
In: Physical Review Letters, 2013, vol. 110, no. 16, p. 166401
Systems of adatoms on semiconductor surfaces display competing ground states and exotic spectral properties typical of two-dimensional correlated electron materials which are dominated by a complex interplay of spin and charge degrees of freedom. We report a fully ab initio derivation of low-energy Hamiltonians for the adatom systems Si(111):X, with X=Sn, Si, C, Pb, that we solve within...
|
In: EPL (Europhysics Letters), 2013, vol. 101, no. 4, p. 47007
We study the response of quantum many-body systems to coupling some of their degrees of freedom to external gauge fields. This serves to understand the current Green functions and transport properties of interacting many-body systems. Our analysis leads to a "gauge theory of states of matter" complementary to the well-known Landau theory of order parameters. We illustrate the power of our...
|
In: Physical Review E, 2013, vol. 87, no. 2, p. 023305
We investigate the possibility to assist the numerically ill-posed calculation of spectral properties of interacting quantum systems in thermal equilibrium by extending the imaginary-time simulation to a finite Schwinger-Keldysh contour. The effect of this extension is tested within the standard maximum entropy approach to analytic continuation. We find that the inclusion of real-time data...
|
