Slave Boson Theory of Orbital Differentiation with Crystal Field Effects: Application toUO2

Abstract

We derive an exact operatorial reformulation of the rotational invariant slave boson method and we apply it to describe the orbital differentiation in strongly correlated electron systems starting from first principles. The approach enables us to treat strong electron correlations, spin-orbit coupling and crystal field splittings on the same footing by exploiting the gauge invariance of the mean-field equations. We apply our theory to the archetypical nuclear fuel UO2, and show that the ground state of this system displays a pronounced orbital differention within the 5f manifold, with Mott localized Γ8 and extended Γ7 electrons.

Rotationally invariant slave-boson and density matrix embedding theory: Unified framework and comparative study on the one-dimensional and two-dimensional Hubbard model

“…Subsequently, it has been also shown 30 that DMET can be formally recovered from the RISB equation derived in Ref. 19 by setting to unity the variational parameters encoding the mass renormalization weights.…”

“…Another important theoretical method widely used for studying strongly correlated electron systems is the rotationally-invariant slave-boson theory (RISB) [17][18][19] , which is equivalent to the multi-orbital Gutzwiller approximation at the mean-field level [20][21][22] and generally provides predictions almost as accurate as DMFT 19,[23][24][25][26][27][28][29] (especially for the ground-state properties) while being much less computationally demanding. Even if the foundation of the RISB mean-field theory is based on seemingly distinct ideas, it turns out that also this framework can be viewed as a quantum-embedding theory.…”

Correlation-driven Lifshitz transition and orbital order in a two-band Hubbard model

“…the conventional Hubbard U , as well as of the higher order multipoles responsible of Hund's rules. For instance, the distinction between different orbitals brought about by the hopping integrals and the crystal field can be amplified by strong correlations, leading to pronounced orbital differentiation [7][8][9][10] , and eventually to the so-called orbital-selective Mott transitions (OSMT) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] where the orbitals with the narrowest bandwidth localise while the others are still itinerant. In addition, orbital degrees of freedom are expected to play an important role in determining which symmetry-broken phase is more likely to accompany the Mott transition when correlations grow at integer electron density.…”

“…(Color online) Schematic representation of the canted AFO phase, assuming that the U (1) symmetry is broken along x, i.e., φ = 0 in Eq (10)…”

Dynamical mean-field theory, density-matrix embedding theory, and rotationally invariant slave bosons: A unified perspective

“…Two particularly successful methods are the (meanfield) rotationally invariant slave-boson method (RISB, [18,19]) and the density-matrix embedding theory (DMET, [20,21]). RISB yields kinetic energy renormalizations, double occupancies and valence histograms very close to DMFT [22][23][24] and has been applied to numerous multiband models [19,[25][26][27] and realistic compounds [27][28][29]. These slave-boson methods have a close connection to the Gutzwiller approximation as shown in Ref.…”