Université de Fribourg

Staggered ordered phases in the three-orbital Hubbard model

Ishigaki, Kosuke ; Nasu, Joji ; Koga, Akihisa ; Hoshino, Shintaro ; Werner, Philipp

In: Physical Review B, 2019, vol. 99, no. 8, p. 085131

We study ordered phases with broken translational symmetry in the half-filled three- orbital Hubbard model with antiferromagnetic Hund coupling by means of dynamical mean-field theory (DMFT) and continuous-time quantum Monte Carlo simulations. The stability regions of the antiferro-orbital (AFO), antiferromagnetic (AFM), and charge density wave (CDW) states are determined by measuring the...

Université de Fribourg

Spin-freezing and the Sachdev-Ye model

Werner, Philipp ; Kim, Aaram J. ; Hoshino, Shintaro

In: EPL (Europhysics Letters), 2018, vol. 124, no. 5, p. 57002

Spin-freezing is the origin of bad-metal physics and non-Fermi liquid (non-FL) properties in a broad range of correlated compounds. In a multi-orbital lattice system with Hund coupling, doping of the half-filled Mott insulator results in a highly incoherent metal with frozen magnetic moments. These moments fluctuate and collapse in a crossover region that is characterized by unusual non-Fermi...

Université de Fribourg

Spontaneously orbital-selective superconductivity in a three-orbital Hubbard model

Ishigaki, Kosuke ; Nasu, Joji ; Koga, Akihisa ; Hoshino, Shintaro ; Werner, Philipp

In: Physical Review B, 2018, vol. 98, no. 23, p. 235120

We study a three-orbital Hubbard model with negative Hund's coupling in infinite dimensions, combining dynamical mean-field theory with continuous time quantum Monte Carlo simulations. This model, which is relevant for the description of alkali- doped fullerides, has previously been shown to exhibit a spontaneous orbital-selective Mott phase in the vicinity of the superconducting phase....

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

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

Long-range orders and spin/orbital freezing in the two-band Hubbard model

Steiner, Karim ; Hoshino, Shintaro ; Nomura, Yusuke ; Werner, Philipp

In: Physical Review B, 2016, vol. 94, no. 7, p. 075107

We solve the orbitally degenerate two-band Hubbard model within dynamical mean field theory and map out the instabilities to various symmetry-broken phases based on an analysis of the corresponding lattice susceptibilities. Phase diagrams as a function of the Hund coupling parameter J are obtained both for the model with rotationally invariant interaction and for the model with Ising-type...

Université de Fribourg

Electronic orders in multiorbital Hubbard models with lifted orbital degeneracy

Hoshino, Shintaro ; Werner, Philipp

In: Physical Review B, 2016, vol. 93, no. 15, p. 155161

We study the symmetry-broken phases in two- and three-orbital Hubbard models with lifted orbital degeneracy using dynamical mean-field theory. On the technical level, we explain how symmetry relations can be exploited to measure the four-point correlation functions needed for the calculation of the lattice susceptibilities. In the half-filled two- orbital model with crystal-field splitting, we...

Université de Fribourg

Superconductivity from emerging magnetic moments

Hoshino, Shintaro ; Werner, Philipp

In: Physical Review Letters, 2015, vol. 115, no. 24, p. 247001

Multiorbital Hubbard models are shown to exhibit a spatially isotropic spin-triplet superconducting phase, where equal-spin electrons in different local orbitals are paired. This superconducting state is stabilized in the spin-freezing crossover regime, where local moments emerge in the metal phase, and the pairing is substantially assisted by spin anisotropy. The phase diagram features a...

Université de Fribourg

Phase diagram of pyrochlore iridates: all-in\char21{}All-out magnetic ordering and non-Fermi-liquid properties

Shinaoka, Hiroshi ; Hoshino, Shintaro ; Troyer, Matthias ; Werner, Philipp

In: Physical Review Letters, 2015, vol. 115, no. 15, p. 156401

We study the prototype 5d pyrochlore iridate Y2Ir2O7 from first principles using the local density approximation and dynamical mean-field theory (LDA+DMFT). We map out the phase diagram in the space of temperature, on-site Coulomb repulsion U, and filling. Consistent with experiments, we find that an all-in–all-out ordered insulating phase is stable for realistic values of U. The trigonal...