33 research outputs found
Variational approach to transport in quantum dots
We have derived a variational principle that defines the nonequilibrium
steady-state transport across a correlated impurity mimicking, e.g., a quantum
dot coupled to biased leads. This variational principle has been specialized to
a Gutzwiller's variational space, and applied to the study of the simple
single-orbital Anderson impurity model at half filling, finding a good
qualitative accord with the observed behavior in quantum dots for the expected
regime of values of the bias. Beyond the purely theoretical interest in the
formal definition of a variational principle in a nonequilibrium problem, the
particular methods proposed have the important advantage to be simple and
flexible enough to deal with more complicated systems and variational spaces.Comment: 15 pages, 4 figure
Time-dependent ghost-Gutzwiller non-equilibrium dynamics
We introduce the time-dependent ghost Gutzwiller approximation (td-gGA), a
non-equilibrium extension of the ghost Gutzwiller approximation (gGA), a
powerful variational approach which systematically improves on the standard
Gutzwiller method by including auxiliary degrees of freedom. We demonstrate the
effectiveness of td-gGA by studying the quench dynamics of the single-band
Hubbard model as a function of the number of auxiliary parameters. Our results
show that td-gGA captures the relaxation of local observables, in contrast with
the time-dependent Gutzwiller method. This systematic and qualitative
improvement leads to an accuracy comparable with time-dependent Dynamical
Mean-Field Theory which comes at a much lower computational cost. These
findings suggest that td-gGA has the potential to enable extensive and accurate
theoretical investigations of multi-orbital correlated electron systems in
nonequilibrium situations, with potential applications in the field of quantum
control, Mott solar cells, and other areas where an accurate account of the
non-equilibrium properties of strongly interacting quantum systems is required.Comment: 8 pages, 2 figure
Critical role of electronic correlations in determining crystal structure of transition metal compounds
The choice that a solid system "makes" when adopting a crystal structure
(stable or metastable) is ultimately governed by the interactions between
electrons forming chemical bonds. By analyzing 6 prototypical binary
transition-metal compounds we demonstrate here that the orbitally-selective
strong -electron correlations influence dramatically the behavior of the
energy as a function of the spatial arrangements of the atoms. Remarkably, we
find that the main qualitative features of this complex behavior can be traced
back to simple electrostatics, i.e., to the fact that the strong -electron
correlations influence substantially the charge transfer mechanism, which, in
turn, controls the electrostatic interactions. This result advances our
understanding of the influence of strong correlations on the crystal structure,
opens a new avenue for extending structure prediction methodologies to strongly
correlated materials, and paves the way for predicting and studying
metastability and polymorphism in these systems.Comment: Main text: 8 pages, 4 figures, 1 table; Supplemental material: 2
pages, 1 figure, 2 table
Principle of maximum entanglement entropy and local physics of strongly correlated materials
We argue that, because of quantum entanglement, the local physics of strongly correlated materials at zero temperature is described in a very good approximation by a simple generalized Gibbs distribution, which depends on a relatively small number of local quantum thermodynamical potentials. We demonstrate that our statement is exact in certain limits and present numerical calculations of the iron compounds FeSe and FeTe and of the elemental cerium by employing the Gutzwiller approximation that strongly support our theory in general
Emergent Bloch excitations in Mott matter
We develop a unified theoretical picture for excitations in Mott systems, portraying both the heavy quasiparticle excitations and the Hubbard bands as features of an emergent Fermi liquid state formed in an extended Hilbert space, which is nonperturbatively connected to the physical system. This observation sheds light on the fact that even the incoherent excitations in strongly correlated matter often display a well-defined Bloch character, with pronounced momentum dispersion. Furthermore, it indicates that the Mott point can be viewed as a topological transition, where the number of distinct dispersing bands displays a sudden change at the critical point. Our results, obtained from an appropriate variational principle, display also remarkable quantitative accuracy. This opens an exciting avenue for fast realistic modeling of strongly correlated materials