arXiv subjects

Llorenç Serra

Publications and source records attributed to Llorenç Serra.

44 records · Page 3Linked to original sources

arXiv2013

Majorana modes and complex band structure of quantum wires

We describe Majorana edge states of a semi-infinite wire using the complex band structure approach. In this method the edge state at a given energy is built as a superposition of evanescent waves. It is shown that the superposition can not always satisfy the required boundary condition, thus restricting the existence of edge modes. We discuss purely 1D and 2D systems, focussing in the latter case on the effect of the Rashba mixing term.

cond-mat.mes-hall↗

arXiv2006

Optical response of two-dimensional few-electron concentric double quantum rings: A local-spin-density-functional theory study

We have investigated the dipole charge- and spin-density response of few-electron two-dimensional concentric nanorings as a function of the intensity of a perpendicularly applied magnetic field. We show that the dipole response displays signatures associated with the localization of electron states in the inner and outer ring favored by the perpendicularly applied magnetic field. Electron localization produces a more fragmented spectrum due to the appearance of additional edge excitations in the inner and outer ring.

cond-mat.mes-hall↗

arXiv2006

Spin-orbit effects in GaAs quantum wells: Interplay between Rashba, Dresselhaus, and Zeeman interactions

The interplay between Rashba, Dresselhaus and Zeeman interactions in a quantum well submitted to an external magnetic field is studied by means of an accurate analytical solution of the Hamiltonian, including electron-electron interactions in a sum rule approach. This solution allows to discuss the influence of the spin-orbit coupling on some relevant quantities that have been measured in inelastic light scattering and electron-spin resonance experiments on quantum wells. In particular, we have evaluated the spin-orbit contribution to the spin splitting of the Landau levels and to the splitting of charge- and spin-density excitations. We also discuss how the spin-orbit effects change if the applied magnetic field is tilted with respect to the direction perpendicular to the quantum well.

cond-mat.mes-hall↗

arXiv2001

Far infrared absorption in triangular and square quantum dots: characterization of corner and side modes

The far-infrared absorption of triangular and square two-dimensional quantum dots is studied by means of time simulations of the density oscillations within the time-dependent local-spin-density approximation. The absorption is spatially analyzed using a local-response theory that allows the identification of {\em corner} and {\em side} modes in the geometric nanostructures. The evolution with a vertical magnetic field of varying intensity is also discussed.

cond-mat.mes-hall↗

arXiv2001

Hartree-Fock dynamics in highly excited quantum dots

Time-dependent Hartree-Fock theory is used to describe density oscillations of symmetry-unrestricted two-dimensional nanostructures. In the small amplitude limit the results reproduce those obtained within a perturbative approach such as the linearized time-dependent Hartree-Fock one. The nonlinear regime is explored by studying large amplitude oscillations in a non-parabolic potential, which are shown to introduce a strong coupling with internal degrees of freedom. This excitation of internal modes, mainly of monopole and quadrupole character, results in sizeable modifications of the dipole absorption.

cond-mat.mes-hall↗

arXiv2001

Magnetic dipole and electric quadrupole responses of elliptic quantum dots in magnetic fields

The magnetic dipole (M1) and electric quadupole (E2) responses of two-dimensional quantum dots with an elliptic shape are theoretically investigated as a function of the dot deformation and applied static magnetic field. Neglecting the electron-electron interaction we obtain analytical results which indicate the existence of four characteristic modes, with different $B$-dispersion of their energies and associated strengths. Interaction effects are numerically studied within the time-dependent local-spin-density theory, assessing the validity of the non-interacting picture.

cond-mat.mes-hall↗

arXiv2001

Ground state and far-infrared absorption of two-electron rings in a magnetic field

Motivated by recent experiments [A. Lorke {\em et al.}, Phys. Rev. Lett.\ {\bf 84}, 2223 (2000)] an analysis of the ground state and far-infrared absorption of two electrons confined in a quantum ring is presented. The height of the repulsive central barrier in the confining potential is shown to influence in an important way the ring properties. The experiments are best explained assuming the presence of both high- and low-barrier quantum rings in the sample. The formation of a two-electron Wigner molecule in certain cases is discussed.

cond-mat.mes-hall↗

arXiv2000

Magnetic Thomas-Fermi-Weizsäcker model for quantum dots: a comparison with Kohn-Sham ground states

The magnetic extension of the Thomas-Fermi-Weizsäcker kinetic energy is used within density-functional-theory to numerically obtain the ground state densities and energies of two-dimensional quantum dots. The results are thoroughly compared with the microscopic Kohn-Sham ones in order to assess the validity of the semiclassical method. Circular as well as deformed systems are considered.

cond-mat.mes-hall↗