Université de Fribourg

Hund’s coupling driven photocarrier relaxation in the two-band Mott insulator

Strand, Hugo U. R. ; Golež, Denis ; Eckstein, Martin ; Werner, Philipp

In: Physical Review B, 2017, vol. 96, no. 16, p. 165104

We study the relaxation dynamics of photocarriers in the paramagnetic Mott insulating phase of the half-filled two-band Hubbard model. Using nonequilibrium dynamical mean-field theory, we excite charge carriers across the Mott gap by a short hopping modulation, and simulate the evolution of the photodoped population within the Hubbard bands. We observe an ultrafast charge-carrier relaxation...

Université de Fribourg

Anisotropic Harper-Hofstadter-Mott model: Competition between condensation and magnetic fields

Hügel, Dario ; Strand, Hugo U. R. ; Werner, Philipp ; Pollet, Lode

In: Physical Review B, 2017, vol. 96, no. 5, p. 054431

We derive the reciprocal cluster mean-field method to study the strongly interacting bosonic Harper-Hofstadter-Mott model. The system exhibits a rich phase diagram featuring band insulating, striped superfluid, and supersolid phases. Furthermore, for finite hopping anisotropy, we observe gapless uncondensed liquid phases at integer fillings, which are analyzed by exact diagonalization. The...

Université de Fribourg

Quantum Monte Carlo impurity solvers for multi-orbital problems and frequency-dependent interactions

Shinaoka, Hiroshi ; Assaad, F. ; Blümer, N. ; Werner, Philipp

In: The European Physical Journal Special Topics, 2017, vol. 226, no. 11, p. 2499–2523

The solution of an auxiliary quantum impurity system is the computationally expensive step in dynamical mean field theory simulations of lattice models and materials. In this review, we discuss Monte Carlo based impurity solvers, which are suitable for a wide range of applications. In particular, we present an efficient implementation of the hybridization expansion approach, which enables the...

Université de Fribourg

Nonequilibrium steady states and transient dynamics of conventional superconductors under phonon driving

Murakami, Yuta ; Tsuji, Naoto ; Eckstein, Martin ; Werner, Philipp

In: Physical Review B, 2017, vol. 96, no. 4, p. 045125

We perform a systematic analysis of the influence of phonon driving on the superconducting Holstein model coupled to heat baths by studying both the transient dynamics and the nonequilibrium steady state (NESS) in the weak and strong electron-phonon coupling regimes. Our study is based on the nonequilibrium dynamical mean-field theory, and for the NESS we present a Floquet formulation ...

Université de Fribourg

Nonequilibrium $GW+\mathrm{EDMFT}$: Antiscreening and Inverted Populations from Nonlocal Correlations

Golež, Denis ; Boehnke, Lewin ; Strand, Hugo U. R. ; Eckstein, Martin ; Werner, Philipp

In: Physical Review Letters, 2017, vol. 118, no. 24, p. 246402

We study the dynamics of screening in photodoped Mott insulators with long-ranged interactions using a nonequilibrium implementation of the GW plus extended dynamical mean-field theory formalism. Our study demonstrates that the complex interplay of the injected carriers with bosonic degrees of freedom (charge fluctuations) can result in long-lived transient states with properties that are...

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

Ultrafast switching of composite order in ${A}_{3}{\mathrm{C}}_{60}$

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

In: Physical Review B, 2017, vol. 95, no. 19, p. 195405

We study the controlled manipulation of the Jahn-Teller metal state of fulleride compounds using nonequilibrium dynamical mean-field theory. This anomalous metallic state is a spontaneous orbital-selective Mott phase, which is characterized by one metallic and two insulating orbitals. Using protocols based on transiently reduced hopping amplitudes or periodic electric fields, we demonstrate...

Université de Fribourg

Spontaneous orbital-selective mott transitions and the Jahn-Teller metal of ${a}_{3}{\mathrm{c}}_{60}$

Hoshino, Shintaro ; Werner, Philipp

In: Physical Review Letters, 2017, vol. 118, no. 17, p. 177002

The alkali-doped fullerides A3C60 are half-filled three-orbital Hubbard systems which exhibit an unconventional superconducting phase next to a Mott insulator. While the pairing is understood to arise from an effectively negative Hund coupling, the highly unusual Jahn-Teller metal near the Mott transition, featuring both localized and itinerant electrons, has not been understood. This...

Université de Fribourg

$\mathbf{J}$ freezing and Hund’s rules in spin-orbit-coupled multiorbital Hubbard models

Kim, Aaram J. ; Jeschke, Harald O. ; Werner, Philipp ; Valentí, Roser

In: Physical Review Letters, 2017, vol. 118, no. 8, p. 086401

We investigate the phase diagram of the spin-orbit-coupled three orbital Hubbard model at arbitrary filling by means of dynamical mean-field theory combined with the continuous-time quantum Monte Carlo method. We find that the spin-freezing crossover occurring in the metallic phase of the nonrelativistic multiorbital Hubbard model can be generalized to a J-freezing crossover, with J=L+S, in...

Université de Fribourg

Continuous-time hybridization expansion quantum impurity solver for multi-orbital systems with complex hybridizations

Shinaoka, Hiroshi ; Gull, Emanuel ; Werner, Philipp

In: Computer Physics Communications, 2017, vol. 215, p. 128–136

We describe an open-source implementation of the continuous-time hybridization- expansion quantum Monte Carlo method for impurity models with general instantaneous two-body interactions and complex hybridization functions. The code is built on an updated version of the core libraries of ALPS (Applications and Libraries for Physics Simulations) [ALPSCore libraries].