In: Journal of Physics: Condensed Matter, 2019, vol. 31, no. 32, p. 323001
The pyrochlore oxides A2B2O7 exhibit a complex interplay between geometrical frustration, electronic correlations, and spin–orbit coupling (SOC), due to the lattice structure and active charge, spin, and orbital degrees of freedom. Understanding the properties of these materials is a theoretical challenge, because their intricate nature depends on materialspecific details and quantum...

In: Physical Review X, 2018, vol. 8, no. 1, p. 011005
Multiferroism can originate from the breaking of inversion symmetry caused by magneticspiral order. The usual mechanism for stabilizing a magnetic spiral is competition between magnetic exchange interactions differing by their range and sign, such as nearestneighbor and nextnearestneighbor interactions. In insulating compounds, it is unusual for these interactions to be both comparable in...

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...

In: Computer Physics Communications, 2017, vol. 215, p. 128–136
We describe an opensource implementation of the continuoustime hybridization expansion quantum Monte Carlo method for impurity models with general instantaneous twobody 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].

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...

In: Physical Review B, 2015, vol. 92, no. 19, p. 195150
Mixed valence spinels provide a fertile playground for the interplay between charge, spin, and orbital degrees of freedom in strongly correlated electrons on a geometrically frustrated lattice. Among them, AlV2O4 and LiV2O4 exhibit contrasting and puzzling behavior: selforganization of sevensite clusters and heavy fermion behavior. We theoretically perform a comparative study of...

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 meanfield theory (LDA+DMFT). We map out the phase diagram in the space of temperature, onsite Coulomb repulsion U, and filling. Consistent with experiments, we find that an allin–allout ordered insulating phase is stable for realistic values of U. The trigonal...

In: Physical Review B, 2015, vol. 91, no. 24, p. 245156
We study the reliability of the constrained randomphase approximation (cRPA) method for the calculation of lowenergy 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 meanfield theory (DMFT) in a...

In: Journal of Statistical Mechanics: Theory and Experiment, 2014, vol. 2014, no. 6, p. P06012
We explore two complementary modifications of the hybridizationexpansion continuoustime Monte Carlo method, aiming at large multiorbital quantum impurity problems. One idea is to compute the imaginarytime 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...
