arXiv subjects

Pawel Hawrylak

Publications and source records attributed to Pawel Hawrylak.

61 records · Page 4Linked to original sources

arXiv2002

Theory of the spin singlet filling factor $ν=2$ quantum Hall droplet

A theory of electronic properties of a spin-singlet quantum Hall droplet at filling factor $ν=2$ in a parabolic quantum dot is developed. The excitation spectrum and the stability of the droplet due to the transfer of electrons into the second Landau level at low magnetic fields and due to spin flip at the edge at higher magnetic fields is determined using Hartree-Fock, exact diagonalisation, and spin-density functional methods. We show that above a critical number of electrons $N_c$ the unpolarised $ν=2$ quantum Hall droplet ceases to be a ground state in favor of spin-polarised phases. We determine the characteristic pattern in the addition and current-amplitude Coulomb blockade spectra associated with the stable $ν=2$ droplet. We show that the spin transition of the droplet at a critical number of electrons is accompanied by the reversal of the current amplitude modulation at the $ν=2$ line, as observed in recent experiments.

cond-mat.mes-hall↗

arXiv2000

Energy spectra and photoluminescence of charged magneto-excitons

Charged magneto-excitons X- in a dilute 2D electron gas in narrow and symmetric quantum wells are studied using exact diagonalization techniques. An excited triplet X- state with a binding energy of about 1 meV is found. This state and the singlet are the two optically active states observed in photoluminescence (PL). The interaction of X-'s with electrons is shown to have short range, which effectively isolates bound X- states from a dilute e-h plasma. This results in the insensitivity of PL to the filling factor nu. For the "dark" triplet X- ground state, the oscillator strength decreases exponentially as a function of 1/nu which explains why it is not seen in PL.

cond-mat.mes-hall↗

arXiv2000

Charged Excitons in a Dilute 2D Electron Gas in a High Magnetic Field

A theory of charged excitons X- in a dilute 2D electron gas in a high magnetic field is presented. In contrast to previous calculations, three bound X- states (one singlet and two triplets) are found in a narrow and symmetric GaAs quantum well. The singlet and a "bright" triplet are the two optically active states observed in experiments. The bright triplet has the binding energy of about 1 meV, smaller than the singlet and a "dark" triplet. The interaction of bound X-'s with a dilute 2D electron gas is investigated using exact diagonalization techniques. It is found that the short-range character of the e:X- interactions effectively isolates bound X- states from a dilute e-h plasma. This results in the insensitivity of the photoluminescence spectrum to the filling factor nu, and an exponential decrease of the oscillator strength of the dark triplet X- as a function of 1/nu$.

cond-mat.mes-hall↗

arXiv1999

Composite Fermion Picture for Multi-Component Plasmas in 2D Electron-Hole Systems in a Strong Magnetic Field

Low lying states of a 2D electron-hole system contain electrons and one or more types of charged excitonic complexes. Binding energies and angular momenta of these excitonic ions, and the pseudopotentials describing their interactions with electrons and with one another are obtained from numerical studies of small systems. Incompressible fluid ground states of such multi-component plasmas are found in exact numerical diagonalizations. A generalized composite Fermion (CF) picture involving Chern--Simons charges and fluxes of different types is proposed and shown to predict the low lying states at any value of the magnetic field.

cond-mat.mes-hall↗

arXiv1998

Incompressible states of negatively charged magneto-excitons

We study the system of up to four negatively charged magneto-excitons (X-'s) in the spherical geometry, using the exact-diagonalization techniques. At low energies, X-'s are bound and behave like charged particles without internal dynamics. The pseudopotential describing X-:X- scattering is almost identical to that of electrons and the low-lying few X- states correspond to the few-electron states. The total angular momentum of the ground state depends on the effective filling factor nu and vanishes at its special values. The analogs to the Laughlin nu=1/3 state and the Jain nu=2/5 state of electrons are found. The X- system is predicted to exhibit the fractional quantum Hall effect.

cond-mat.mes-hall↗

arXiv1998

Excitonic Ions and Pseudopotentials in 2D Systems: Evidence for Quantum Hall States of an X- Gas

Systems of up to twelve electrons and six holes on the Haldane sphere are studied by exact numerical diagonalization. The low lying states of the system involve bound excitonic complexes such as (X^n)-. The angular momenta of these complexes and the pseudopotentials describing their interaction are determined. The similarity to the electron pseudopotential suggests the possibility of incompressible ground states of a gas of X- ions for nu<=1/3. The nu=1/3 state of three X-'s is found.

cond-mat.mes-hall↗

arXiv1994

Correlated few-electron states in vertical double-quantum-dot systems

The electronic properties of semiconductor, vertical, double quantum dot systems with few electrons are investigated by means of analytic, configuration-interaction, and mean-field methods. The combined effect of a high magnetic field, electrostatic confinement, and inter-dot coupling, induces a new class of few-electron ground states absent in single quantum dots. In particular, the role played by the isospin (or quantum dot index) in determining the appearance of new ground states is analyzed and compared with the role played by the standard spin.

cond-mat↗