Université de Fribourg

Ultrafast doublon dynamics in photoexcited $1T$-${\mathrm{TaS}}_{2}$

Ligges, M. ; Avigo, I. ; Gole?, Denis ; Strand, H. ?U.? R. ; Beyazit, Y. ; Hanff, K. ; Diekmann, F. ; Stojchevska, L. ; Kalläne, M. ; Zhou, P. ; Rossnagel, K. ; Eckstein, Martin ; Werner, Philipp ; Bovensiepen, U.

In: Physical Review Letters, 2018, vol. 120, no. 16, p. 166401

Strongly correlated materials exhibit intriguing properties caused by intertwined microscopic interactions that are hard to disentangle in equilibrium. Employing nonequilibrium time-resolved photoemission spectroscopy on the quasi-two- dimensional transition-metal dichalcogenide 1T-TaS2, we identify a spectroscopic signature of doubly occupied sites (doublons) that reflects fundamental Mott...

Université de Fribourg

Nonthermal switching of charge order: Dynamical slowing down and optimal control

Schüler, Michael ; Murakami, Yuta ; Werner, Philipp

In: Physical Review B, 2018, vol. 97, no. 15, p. 155136

We investigate the laser-induced dynamics of electronically driven charge-density- wave (CDW) order. A comprehensive mean-field analysis of the attractive Hubbard model in the weak-coupling regime reveals ultrafast switching and ultrafast melting of the order via a nonthermal pathway. The resulting nonequilibrium phase diagram exhibits multiple distinct regimes of the order parameter dynamics...

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

Spreading of correlations in the Falicov-Kimball model

Herrmann, Andreas J. ; Antipov, Andrey E. ; Werner, Philipp

In: Physical Review B, 2018, vol. 97, no. 16, p. 165107

We study dynamical properties of the one- and two-dimensional Falicov-Kimball model using lattice Monte Carlo simulations. In particular, we calculate the spreading of charge correlations in the equilibrium model and after an interaction quench. The results show a reduction of the light-cone velocity with interaction strength at low temperature, while the phase velocity increases. At higher...

Université de Fribourg

Floquet prethermalization in the resonantly driven Hubbard model

Herrmann, Andreas ; Murakami, Yuta ; Eckstein, Martin ; Werner, Philipp

In: EPL (Europhysics Letters), 2017, vol. 120, no. 5, p. 57001

We demonstrate the existence of long-lived prethermalized states in the Mott insulating Hubbard model driven by periodic electric fields. These states, which also exist in the resonantly driven case with a large density of photo-induced doublons and holons, are characterized by a nonzero current and an effective temperature of the doublons and holons which depends sensitively on the driving...

Université de Fribourg

Photoinduced enhancement of excitonic order

Murakami, Yuta ; Golež, Denis ; Eckstein, Martin ; Werner, Philipp

In: Physical Review Letters, 2017, vol. 119, no. 24, p. 247601

We study the dynamics of excitonic insulators coupled to phonons using the time- dependent mean-field theory. Without phonon couplings, the linear response is given by the damped amplitude oscillations of the order parameter with a frequency equal to the minimum band gap. A phonon coupling to the interband transfer integral induces two types of long-lived collective oscillations of the...

Université de Fribourg

Pressure-driven insulator-metal transition in cubic phase UO 2

Huang, Li ; Wang, Yilin ; Werner, Philipp

In: EPL (Europhysics Letters), 2017, vol. 119, no. 5, p. 57007

Understanding the electronic properties of actinide oxides under pressure poses a great challenge for experimental and theoretical studies. Here, we investigate the electronic structure of cubic phase uranium dioxide at different volumes using a combination of density functional theory and dynamical mean-field theory. The ab initio calculations predict an orbital-selective insulator-metal...

Université de Fribourg

Multitier self-consistent $GW+\text{EDMFT}$

Nilsson, Fredrik ; Boehnke, Lewin ; Werner, Philipp ; Aryasetiawan, Ferdi

In: Physical Review Materials, 2017, vol. 1, no. 4, p. 043803

We discuss a parameter-free and computationally efficient ab initio simulation approach for moderately and strongly correlated materials, the multitier self-consistent GW+EDMFT method. This scheme treats different degrees of freedom, such as high- energy and low-energy bands, or local and nonlocal interactions, within appropriate levels of approximation, and provides a fully self-consistent...