Minchul Lee

Spin-orbit interaction in symmetric wells with two subbands.

We investigate the spin-orbit (SO) interaction in two-dimensional electron gases in quantum wells with two subbands. From the 8x8 Kane model, we derive a new intersubband-induced SO term which resembles the functional form of the Rashba SO but is nonzero even in symmetric structures. This follows from the distinct parity of the confined states (even or odd) which obliterates the need for asymmetric potentials. We self-consistently calculate the new SO coupling strength for realistic wells and find it comparable to the usual Rashba constant. Our new SO term gives rise to a nonzero ballistic spin-Hall conductivity, which changes sign as a function of the Fermi energy (epsilonF) and can induce an unusual Zitterbewegung with cycloidal trajectories without magnetic fields.

Kondo effect and Josephson current through a quantum dot between two superconductors

We investigate the supercurrent through a quantum dot for the whole range of couplings using the numerical renormalization group method. We find that the Josephson current switches abruptly from a

Probing spin and orbital kondo effects with a mesoscopic interferometer

\pi

Spin filter using a semiconductor quantum ring side coupled to a quantum wire

- to a 0-phase as the coupling increases. At intermediate couplings the total spin in the ground state depends on the phase difference between the two superconductors. Our numerical results can explain the crossover in the conductance observed experimentally by Buitelaar \textit{et al.} [Phys. Rev. Lett. \textbf{89}, 256 801 (2002)].

Ballistic spin currents in mesoscopic metal/In(Ga)As/metal junctions

We investigate theoretically the transport properties of a closed Aharonov-Bohm interferometer containing two quantum dots in the strong coupling regime. We find two distinct physical scenarios depending on the strength of the interdot Coulomb interaction. When the interdot Coulomb interaction is negligible only spin fluctuations are important and each dot develops a Kondo resonance at the Fermi level independently of the applied magnetic flux. The transport is characterized by the interference of these two independent Kondo resonances. On the contrary, for large interdot interaction, only one electron can be accommodated onto the double dot system. In this situation, not only the spin can fluctuate but also the orbital degree of freedom (the pseudo-spin). As a result, we find different ground states depending on the value of the applied flux. When

Thermoelectrical detection of Majorana states

\phi=\pi

Magnetic-field asymmetry of nonlinear thermoelectric and heat transport

(mod

Josephson effect through a multilevel quantum dot near a singlet-triplet transition

2\pi

Effect of many-body correlations on mesoscopic charge relaxation

) (

Josephson Effect through an isotropic magnetic molecule

\phi=2\pi\Phi/\Phi_0