Université de Fribourg

Entropy-cooled nonequilibrium states of the Hubbard model

Werner, Philipp ; Li, Jianju ; Golež, Denis ; Eckstein, Martin

In: Physical Review B, 2019, vol. 100, no. 15, p. 155130

We show that the recently proposed cooling-by-doping mechanism allows one to efficiently prepare interesting nonequilibrium states of the Hubbard model. Using nonequilibrium dynamical mean field theory and a particle-hole symmetric setup with dipolar excitations to full and empty bands we produce cold photodoped Mott insulating states with a sharp Drude peak in the optical conductivity, a ...

Université de Fribourg

Dynamics of photodoped charge transfer insulators

Golež, Denis ; Boehnke, Lewin ; Eckstein, Martin ; Werner, Philipp

In: Physical Review B, 2019, vol. 100, no. 4, p. 041111

We study the dynamics of charge transfer insulators after photoexcitation using the three-band Emery model and a nonequilibrium extension of Hartree-Fock + EDMFT (extended dynamical mean field theory) and GW + EDMFT. While the equilibrium properties are accurately reproduced by the Hartree-Fock treatment of the ligand bands, dynamical correlations are essential for a proper description of the...

Université de Fribourg

Comparative study of nonequilibrium insulator-to-metal transitions in electron-phonon systems

Sayyad, Sharareh ; Žitko, Rok ; Strand, Hugo U. R. ; Werner, Philipp ; Golež, Denis

In: Physical Review B, 2019, vol. 99, no. 4, p. 045118

We study equilibrium and nonequilibrium properties of electron-phonon systems described by the Hubbard-Holstein model using dynamical mean-field theory. In equilibrium, we benchmark the results for impurity solvers based on the one-crossing approximation and slave-rotor approximation against non-perturbative numerical renormalization group reference data. We also examine how well the...

Université de Fribourg

Theory of photoinduced ultrafast switching to a spin-orbital ordered hidden phase

Li, Jiajun ; Strand, Hugo U.R. ; Werner, Philipp ; Eckstein, Martin

In: Nature Communications, 2018, vol. 9, no. 1, p. 4581

Photo-induced hidden phases are often observed in materials with intertwined orders. Understanding the formation of these non-thermal phases is challenging and requires a resolution of the cooperative interplay between different orders on the ultra-short timescale. In this work, we demonstrate that non-equilibrium photo-excitations can induce a state with spin-orbital orders entirely...

Université de Fribourg

Enhanced pairing susceptibility in a photodoped two-orbital Hubbard model

Werner, Philipp ; Strand, Hugo U. R. ; Hoshino, Shintaro ; Murakami, Yuta ; Eckstein, Martin

In: Physical Review B, 2018, vol. 97, no. 16, p. 165119

Local spin fluctuations provide the glue for orbital-singlet spin-triplet pairing in the doped Mott insulating regime of multiorbital Hubbard models. At large Hubbard repulsion U, the pairing susceptibility is nevertheless tiny because the pairing interaction cannot overcome the suppression of charge fluctuations. Using nonequilibrium dynamical mean field simulations of the two-orbital...

Université de Fribourg

Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory

Ayral, Thomas ; Biermann, Silke ; Werner, Philipp ; Boehnke, Lewin

In: Physical Review B, 2017, vol. 95, no. 24, p. 245130

In electronic systems with long-range Coulomb interaction, the nonlocal Fock- exchange term has a band-widening effect. While this effect is included in combined many-body perturbation theory and dynamical mean field theory (DMFT) schemes, it is not taken into account in standard extended DMFT (EDMFT) calculations. Here, we include this instantaneous term in both approaches and investigate its...

Université de Fribourg

Nonthermal Melting of Néel Order in the Hubbard Model

Balzer, Karsten ; Wolf, F. Alexander ; McCulloch, Ian P. ; Werner, Philipp ; Eckstein, Martin

In: Physical Review X, 2015, vol. 5, no. 3, p. 031039

Symmetry-broken states such as magnetic order and superconductivity are the hallmark of complex properties in solids. An intriguing new direction in condensed-matter physics is to manipulate these properties on the fastest possible time scales using ultrashort laser pulses. Theoretically, however, the collective many-particle dynamics that is responsible for the formation and melting of...

Université de Fribourg

Dynamics of screening in photodoped Mott insulators

Golež, Denis ; Eckstein, Martin ; Werner, Philipp

In: Physical Review B, 2015, vol. 92, no. 19, p. 195123

We use a nonequilibrium implementation of extended dynamical mean-field theory in combination with a noncrossing approximation impurity solver to study the effect of dynamical screening in photoexcited Mott insulators. The insertion of doublons and holes adds low-energy screening modes and leads to a reduction of the Mott gap. The coupling to low-energy bosonic modes furthermore opens new...

Université de Fribourg

Nonequilibrium dynamical mean-field theory and its applications

Aoki, Hideo ; Tsuji, Naoto ; Eckstein, Martin ; Kollar, Marcus ; Oka, Takashi ; Werner, Philipp

In: Reviews of Modern Physics, 2014, vol. 86, no. 2, p. 779–837

The study of nonequilibrium phenomena in correlated lattice systems has developed into one of the most active and exciting branches of condensed matter physics. This research field provides rich new insights that could not be obtained from the study of equilibrium situations, and the theoretical understanding of the physics often requires the development of new concepts and methods. On the...

Université de Fribourg

Double occupancy and magnetic susceptibility of the Anderson impurity model out of equilibrium

Dirks, Andreas ; Schmitt, S. ; Han, J. E. ; Anders, F. ; Werner, Philipp ; Pruschke, Thomas

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...