J. Silva-Valencia

Impurity states in a spherical GaAs-Ga 1-x Al x As quantum dots: Effects of hydrostatic pressure

We calculated the binding energies of shallow donors and acceptors in a spherical GaAs-Ga1-xAlxAs quantum dot under isotropic hydrostatic pressure for both a finite and an infinitely high barrier. We use a variational approach within the effective mass approximation. The binding energy is computed as a function of hydrostatic pressure, the dot sizes and the impurity position. The results show that the impurity binding energy increases with the pressure for any position of the impurity. We have also found that the binding energy depends on the location of the impurity and the pressure effects are less pronounced for impurities on the edge.

Critical points of the anyon-Hubbard model

Anyons are particles with fractional statistics that exhibit a nontrivial change in the wave function under an exchange of particles. Anyons can be considered to be a general category of particles that interpolate between fermions and bosons. We determined the position of the critical points of the one-dimensional anyon-Hubbard model, which was mapped to a modified Bose-Hubbard model where the tunneling depends on the local density and the interchange angle. We studied the latter model by using the density-matrix renormalization-group method and observed that gapped (Mott insulator) and gapless (superfluid) phases characterized the phase diagram, regardless of the value of the statistical angle. The phase diagram for higher densities was calculated and showed that the Mott lobes increase (decrease) as a function of the statistical angle (global density). The position of the critical point separating the gapped and gapless phases was found using quantum information tools, namely the block von Neumann entropy. We also studied the evolution of the critical point with the global density and the statistical angle and showed that the anyon-Hubbard model with a statistical angle

Phase Evolution of the Electronic Transmission Through a Kondo Correlated Quantum Dot

\ensuremath{\theta}=\ensuremath{\pi}/4

Spin-dependent beating patterns in thermoelectric properties : filtering the carriers of the heat flux in a Kondo adatom system

is in the same universality class as the Bose-Hubbard model with two-body interactions.

Lateral Fano resonance and Kondo effect in the strong coupling regime of a quantum dot embedded in a quantum wire

We study the scattering phase shift of the Kondo assisted transmission through a quantum dot (QD), considering a model that includes an additional non resonant channel transmission. To compute the phase evolution and the transmission amplitude of the QD, for different temperatures, we describe the QD employing the single Anderson impurity model in the limit of infinity Coulomb repulsion, within the X-boson approach. Our results are consistent with the development of an unusually large phase evolution at around p in the Kondo valley, observed in recent experiments, and is consistent with others theoretical treatments.

Spin-1 Bose–Hubbard model with two- and three-body interactions

model in combination with the atomic approach for the Green’s functions. Due to the spin dependence of the Fermi wave numbers, the electrical and thermal conductances together with thermopower and Lorenz number reveal beating patterns as a function of the STM tip position in the Kondo regime. In particular, by tuning the lateral displacement of the tip with respect to the adatom vicinity, the temperature, and the position of the adatom level, one can change the sign of the Seebeck coefficient through charge and spin. This opens a possibility of the microscopic control of the heat flux analogously to that established for the electrical current.

Mott insulator and superfluid phases in bosonic superlattices

We study the electronic transport through a quantum wire (QW), described by a tight-binding chain, with an embedded quantum dot (QD). We obtain the conductance with a strong Fano resonance; the density of states shows that this behavior is linked to a many-body renormalized QD resonant level Ẽf at the edge of the conduction band (CB), strongly hybridized with the Van Hove peaks of the one-dimensional density of states for the lead. The obtained Fano resonance is thermically activated, above the Kondo temperature; this is due to the quantum interference between the CB and a thermal activated channel created by the QD resonance at the vicinity of the bottom of the CB. Our results are in qualitative agreement with those reported for a T-coupled QD.

Phase diagram of the Kondo lattice model with a superlattice potential

Abstract We investigated the ground state of spin-1 bosons interacting under local two- and three-body interactions in one dimension by means of the density matrix renormalization group method. We found that the even–odd asymmetry will be obtained or not depending on the relative values of the two- and three-body interactions. The Mott insulator lobes are spin isotropic, the first showing a dimerized pattern and the second being composed of singlets. The three-body interactions disfavor a longitudinal polar superfluid and a quantum phase transition to a transverse polar superfluid occurs, which could be continuous or discontinuous.

Phase diagrams of bosonic ABn chains

We study the ground-state phase diagram of boson chains on a 2-period superlattice using the density matrix renormalization group method. New insulators for commensurate densities were found, differentiated by the arrangement of the particles in the unit cell, which was corroborated by analysis of the density versus the potential strength. Also, phase transitions between insulators for ρ ≥ 1 were seen, and a maximum in the behavior of the von Neumann entropy in the critical region was revealed, which suggests a superfluid phase between the insulators.

Effect of the repulsion interaction on the ground-state of the Kondo lattice model with a superlattice potential

We study the ground state of a Kondo lattice model where the free carries undergo a superlattice potential. Using the density matrix renormalization group method, we establish that the model exhibits a ferromagnetic phase and spiral phase whose boundaries in the phase diagram depend on the depth of the potential. Also, we observed that the spiral to ferromagnetic quantum phase transition can be tuned by changing the local coupling or the superlattice strength.