Consortium of Swiss Academic Libraries

A Classical Picture of the Role of Vacancies andInterstitials inHelium-4

Ma, Ping ; Pollet, Lode ; Troyer, Matthias ; Zhang, Fu

In: Journal of Low Temperature Physics, 2008, vol. 152, no. 5-6, p. 156-163

Université de Fribourg

Multiferroic magnetic spirals induced by random magnetic exchanges

Scaramucci, Andrea ; Shinaoka, Hiroshi ; Mostovoy, Maxim V. ; Müller, Markus ; Mudry, Christopher ; Troyer, Matthias ; Spaldin, Nicola A.

In: Physical Review X, 2018, vol. 8, no. 1, p. 011005

Multiferroism can originate from the breaking of inversion symmetry caused by magnetic-spiral order. The usual mechanism for stabilizing a magnetic spiral is competition between magnetic exchange interactions differing by their range and sign, such as nearest-neighbor and next-nearest-neighbor interactions. In insulating compounds, it is unusual for these interactions to be both comparable in...

Université de Fribourg

Fidelity susceptibility perspective on the Kondo effect and impurity quantum phase transitions

Wang, Lei ; Shinaoka, Hiroshi ; Troyer, Matthias

In: Physical Review Letters, 2015, vol. 115, no. 23, p. 236601

The Kondo effect is a ubiquitous phenomenon appearing at low temperature in quantum confined systems coupled to a continuous bath. Efforts in understanding and controlling it have triggered important developments across several disciplines of condensed matter physics. A recurring pattern in these studies is that the suppression of the Kondo effect often results in intriguing physical phenomena...

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...

Université de Fribourg

Accuracy of downfolding based on the constrained random-phase approximation

Shinaoka, Hiroshi ; Troyer, Matthias ; Werner, Philipp

In: Physical Review B, 2015, vol. 91, no. 24, p. 245156

We study the reliability of the constrained random-phase approximation (cRPA) method for the calculation of low-energy effective Hamiltonians by considering multiorbital lattice models with one strongly correlated “target” band and two weakly correlated “screening” bands. The full multiorbital system and the effective model are solved within dynamical mean-field theory (DMFT) in a...

Université de Fribourg

Hybridization expansion Monte Carlo simulation of multi-orbital quantum impurity problems: matrix product formalism and improved sampling

Shinaoka, Hiroshi ; Dolfi, Michele ; Troyer, Matthias ; Werner, Philipp

In: Journal of Statistical Mechanics: Theory and Experiment, 2014, vol. 2014, no. 6, p. P06012

We explore two complementary modifications of the hybridization-expansion continuous-time Monte Carlo method, aiming at large multi-orbital quantum impurity problems. One idea is to compute the imaginary-time propagation using a matrix product state representation. We show that bond dimensions considerably smaller than the dimension of the Hilbert space are sufficient to obtain accurate results...

Université de Fribourg

Critical temperature of interacting Bose gases in periodic potentials

Nguyen, T. T. ; Herrmann, Andreas Johannes ; Troyer, Matthias ; Pilati, S.

In: Physical Review Letters, 2014, vol. 112, no. 17, p. 170402

The superfluid transition of a repulsive Bose gas in the presence of a sinusoidal potential which represents a simple-cubic optical lattice is investigated using quantum Monte Carlo simulations. At the average filling of one particle per well the critical temperature has a nonmonotonic dependence on the interaction strength, with an initial sharp increase and a rapid suppression at strong...

Université de Fribourg

From the Cooper Problem to Canted Supersolids in Bose-Fermi Mixtures

Anders, Peter ; Werner, Philipp ; Troyer, Matthias ; Sigrist, Manfred ; Pollet, Lode

In: Physical Review Letters, 2012, vol. 109, no. 20, p. 206401

We calculate the phase diagram of the Bose-Fermi Hubbard model on the 3d cubic lattice at fermionic half filling and bosonic unit filling by means of single-site dynamical mean-field theory. For fast bosons, this is equivalent to the Cooper problem in which the bosons can induce s-wave pairing between the fermions. We also find miscible superfluid and canted supersolid phases depending on the...