Examining phase stabilities and phase equilibria in strongly correlated materials asks for a next level in the many-body extensions to the local-density approximation (LDA) beyond mainly spectroscopic assessments. Here we put the charge self-consistent LDA+dynamical mean-field theory (DMFT) methodology based on projected local orbitals for the LDA+DMFT interface and a tailored pseudopotential framework into action in order to address such thermodynamics of realistic strongly correlated systems. Namely a case study for the electronic phase diagram of the well-known prototype Mott-phenomena system V2O3 at higher temperatures is presented. We are able to describe the first-order metal-to-insulator transitions with negative pressure and temperature from the self-consistent computation of the correlated total energy in line with experimental findings.

The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show that the prototype Mott–Hubbard material V2O3 presents a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds. For both the insulating and the metallic phase, the formation of the transient configuration is triggered by the excitation of electrons into the bonding a1g orbital, and is then stabilized by a lattice distortion characterized by a hardening of the A1g coherent phonon, in stark contrast with the softening observed upon heating. Our results show the importance of selective electron–lattice interplay for the ultrafast control of material parameters, and are relevant for the optical manipulation of strongly correlated systems.

We shed light on the interplay between structure and many-body effects relevant for itinerant ferromagnetism in LaAlO3/SrTiO3 heterostructures. The realistic correlated electronic structure is studied by means of the (spin-polarized) charge self-consistent combination of density functional theory (DFT) with dynamical mean-field theory (DMFT) beyond the realm of static correlation effects. Though many-body behavior is also active in the defect-free interface, a ferromagnetic instability occurs only with oxygen vacancies. A minimal Ti two-orbital eg-t2g description for the correlated subspace is derived. Magnetic order affected by quantum fluctuations builds up from effective double exchange between modified nearly-localized eg and mobile xy electrons.

The correlated electronic structure of the submonolayer surface systems Sn/Si͑111͒ and Sn/Ge͑111͒ is investigated by density-functional theory and its combination with explicit many-body methods. Namely, the dynamical mean-field theory and the slave-boson mean-field theory are utilized for the study of the intriguing interplay between structure, bonding, and electronic correlation. In this respect, explicit low-energy one-and four͑sp 2 -like͒-band models are derived using maximally localized Wannier͑-type͒ functions. In view of the possible low-dimensional magnetism in the Sn submonolayers we compare different types of magnetic orders and indeed find a 120°noncollinear ordering to be stable in the ground state. With single-site methods and cellular-cluster extensions the influence of a finite Hubbard U on the surface states in a planar and a reconstructed structural geometry is furthermore elaborated.

Vanadium Sesquioxide (V2O3) is an antiferromagnetic insulator below TN ≈ 155 K. The magnetic order is not of C-or G-type as one would infer from the bipartite character of the hexagonal basal plane in the high-temperature corundum structure. In fact, the Néel transition is accompanied by a monoclinic distortion that makes one bond of the honeycomb plane inequivalent from the other two, thus justifying a magnetic structure with one ferromagnetic bond and two antiferromagnetic ones. We show here that the magnetic ordering, the accompanying monoclinic structural distortion, the magnetic anisotropy and also the recently discovered high-pressure monoclinic phase, can all be accurately described by conventional electronic structure calculations within GGA and GGA+U. Our results are in line with DMFT calculations for the paramagnetic phase 1 , which predict that the insulating character is driven by a correlation-enhanced crystal field splitting between e π g and a1g orbitals that pushes the latter above the chemical potential. We find that the a1g orbital, although almost empty in the insulating phase, is actually responsible for the unusual magnetic order as it leads to magnetic frustration whose effect is similar to a next-nearest-neighbor exchange in a Heisenberg model on a honeycomb lattice.