I. Grosu

Kondo effect in spin-orbit mesoscopic interferometers

We consider a flux-threaded Aharonov-Bohm ring with an embedded quantum dot coupled to two normal leads. The local Rashba spin-orbit interaction acting on the dot electrons leads to a spin-dependent phase factor in addition to the Aharonov-Bohm phase caused by the external flux. Using the numerical renormalizationgroup method, we find a splitting of the Kondo resonance at the Fermi level which can be compensated by an external magnetic field. To fully understand the nature of this compensation effect, we perform a scaling analysis and derive an expression for the effective magnetic field. The analysis is based on a tight-binding model which leads to an effective Anderson model with a spin-dependent density of states for the transformed lead states. We find that the effective field originates from the combined effect of Rashba interaction and magnetic flux and that it contains important corrections due to electron-electron interactions. We show that the compensating field is an oscillatory function of both the spin-orbit and the Aharonov-Bohm phases. Moreover, the effective field never vanishes due to the particle-hole symmetry breaking independently of the gate voltage.

Localized magnetic states in Rashba dots

Instituto de F´isica Interdisciplinar y Sistemas Complejos (CSIC-UIB), E-07122 Palma de Mallorca, Spain(Dated: February 16, 2009)We study the formation of local moments in quantum dots arising in quasi-one dimensional elec-tron wires due to localized spin-orbit (Rashba) interaction. Using an Anderson-like model to describethe occurrence of the magnetic moments in these Rashba dots, we calculate the local magnetizationwithin the mean-field approximation. We find that the magnetization becomes a nontrivial func-tion of the Rashba coupling strength. We discuss both the equilibrium and nonequilibrium cases.Interestingly, we obtain a magnetic phase which is stable at large bias due to the Rashba interaction.

The Gap-to- Tc Ratio of a van Hove Superconductor

We give an analytical expression for the gap-to-Tc ratio (R) of a superconductor with a van Hove singularity in the density of states. Our calculation yields R in very good agreement with the results obtained numerically by S. Ratanaburi et al. [J. Supercond. 9, 485 (1996)].

Superconductivity and critical coupling in non-Fermi liquids

The critical temperature of a superconductor with a non-Fermi liquid ground state has been calculated. The density of states has two different forms and is energy dependent. The critical values of the coupling factor λ were calculated. The constant density of states results are obtained as particular cases. These results are an extension of the work done by Grosu et al. [Phys. Rev. B56, 8298 (1997)].

NMR parameters in gapped graphene systems

We calculate the nuclear spin-lattice relaxation time and the Knight shift for the case of gapped graphene systems. Our calculations consider both the massive and massless gap scenarios. Both the spin-lattice relaxation time and the Knight shift depend on temperature, chemical potential, and the value of the electronic energy gap. In particular, at the Dirac point, the electronic energy gap has stronger effects on the system nuclear magnetic resonance parameters in the case of the massless gap scenario. Differently, at large values of the chemical potential, both gap scenarios behave in a similar way and the gapped graphene system approaches a Fermi gas from the nuclear magnetic resonance parameters point of view. Our results are important for nuclear magnetic resonance measurements that target the 13C active nuclei in graphene samples.

Field-induced Bose-Einstein condensation of interacting dilute magnons in three-dimensional spin systems : A renormalization-group study

We use the renormalization-group method to study the magnetic field influence on the Bose-Einstein condensation of interacting dilute magnons in three-dimensional spin systems. We first considered a model with

Zero temperature conductance of parallel T-shape double quantum dots

SU(2)

Fluctuation conductivity in layered d-wave superconductors near critical disorder

symmetry (universality class

Thermoelectric transport properties in graphene connected molecular junctions

z=1

Fano interferences in the transport properties of triple quantum dot T-shaped systems

) and we obtain for the critical magnetic field a power law dependence on the critical temperature,