Slave Boson Model Research Articles

Numerical optimization algorithm for rotationally invariant multi-orbital slave-boson method

We develop a generalized numerical optimization algorithm for the rotationally invariant multi-orbital slave boson approach, which is applicable for arbitrary boundary constraints of high-dimensional objective function by combining several classical optimization techniques. After constructing the calculation architecture of rotationally invariant multi-orbital slave boson model, we apply this optimization algorithm to find the stable ground state and magnetic configuration of two-orbital Hubbard models. The numerical results are consistent with available solutions, confirming the correctness and accuracy of our present algorithm. Furthermore, we utilize it to explore the effects of the transverse Hund’s coupling terms on metal–insulator transition, orbital selective Mott phase and magnetism. These results show the quick convergency and robust stable character of our algorithm in searching the optimized solution of strongly correlated electron systems.

Formation of vortices in a dense Bose-Einstein condensate

AbstractA relaxation method is employed to study a rotating dense Bose-Einstein conden-sate beyond Thomas-Fermi approximation. We use a slave-boson model to describethe strongly interacting condensate and derive a generalized non-linear Schr¨odingerequation with kinetic term for the rotating condensate. In comparison with previ-ous calculations, based on Thomas-Fermi approximation, significant improvementsare found in regions, where the condensate in a trap potential is not smooth. Thecritical angular velocity of the vortex formation is higher than in the Thomas-Fermiprediction. 1 Introduction The appearance of vortices in a rotating dilute Bose-Einstein condensate (BEC) is a phe-nomenon that is intrinsically related to the existence of superfluidity [1, 2]. This has beenintensively studied [3, 4] after the achievement of BEC in alkali-metal gases [5, 6]. Thevortex formation can be understood as a local suppression of the BEC due to rotation. Ithappens when the angular velocity Ω exceeds a critical value Ω

A slave boson model for two-dimensional trapped Bose–Einstein condensate

A system of N bosons in a two-dimensional harmonic trap is considered. The system is treated in terms of the slave boson representation for hard-core bosons which is valid in the arbitrary density regimes. I discuss the consequences of higher order interactions on the density profiles by mapping the slave boson equation to the known Kohn–Sham-type equation within the density functional scheme.

Vortex state in a doped Mott insulator

We analyze the recent vortex core spectroscopy experiments in cuprate superconductor and discuss what can be learned from them about the nature of the ground state in these compounds. We argue that the data are inconsistent with the assumption of a simple metallic ground state and exhibit characteristics of a doped Mott insulator. A theory for a vortex core in such a doped Mott insulator is developed based on the U(1) gauge field slave boson model and is shown to exhibit properties qualitatively consistent with the experimental data.

Tunneling density of states of high T(c) superconductors: d-wave BCS model versus SU(2) slave-boson model

Motivated by recent experimental measurements of the tunneling characteristics of high T(c) materials using scanning tunneling spectroscopy, we have calculated the I-V and differential conductance curves in the superconducting state at zero temperature. Comparing BCS-like d-wave pairing and the SU(2) slave-boson approach, we find that the slave-boson model can explain the asymmetric background observed in experiments. The slave-boson model also predicts that the height of the conductance peak relative to the background is proportional to the hole doping concentration x, at least for underdoped samples. We also observe the absence of the van Hove singularity, and comment on possible implications.

Theory of Quasiparticles in the Underdoped High-TcSuperconducting State

The microscopic theory of the superconducting state in the SU(2) slave-boson model is developed. We show how the pseudogap and Fermi surface segments in the normal state develop into a $d\ensuremath{-}\mathrm{wave}$ gap in the superconducting state. Even though the superfluid density is of order $x$ (the doping concentration), the physical properties of the low lying quasiparticles are found to resemble those in BCS theory. Thus the microscopic theory lays the foundation for our earlier phenomenological discussion of the unusual superconducting properties in the underdoped cuprates.

Van Hove exciton-cageons and high-T c superconductivity XA. Role of spin-orbit coupling in generating a diabolical point

Spin-orbit coupling plays a large role in stabilizing the low-temperature orthorhombic phase of La 2− x Sr x CuO 4. It splits the degeneracy of the van Hove singularities (thereby stabilizing the distorted phase) and completely changes the shape of the Fermi surfaces, potentially introducing diabolical points into the band structure. The present paper gives a detailed account of the resulting electronic structure. A slave-boson calculation shows how these results are modified in the presence of strong correlation effects. A scaling regime, found very close ti the metal-insulator transition, allows an analytical determination to be made of the crossover, in the limit of zero oxygen-oxygen hopping, t oo→0. Extreme care must be exercised in choosing the parameters of the three-band model. In particular, t oo is renormalized from its LDA value. Furthermore, it is suggested that the slave-boson model be spin corrected, in which case the system is close to a metal-insulator transition at half filling.

The electrical resistivity of the two-conduction-band heavy-fermion alloy system

The electrical resistivity of the heavy-fermion alloys is calculated through a two-conduction-band slave boson model using the self-consistent coherent potential approximation method. The results indicate that for very low temperatures the resistivity of the alloy system follows the rho 0+AT2 law and the coefficient A changes from negative values to positive values as the alloy concentration increases. The occurrence of the resistivity maximum at a finite temperature is also obtained on increasing the concentration of heavy-fermion alloys.

Phase separation near the mott transition in La 2-x Sr x CuO 4

Evidence is presented for the importance of a large density-of-states (dos) peak (due to the van Hove singularity) in the copper oxide ceramic superconductors. A slave boson model is introduced, which can describe the insulating transition in the half-filled band, yet properly describe the Fermi liquid state away from half filling. The dos peak induces an inhomogeneous phase, by a mechanism related to Hume-Rothery phase formation in alloys.