A. S. Zhuravlev

Antiphased Cyclotron-Magnetoplasma Mode in a Quantum Hall System

Max-Planck-Institut fu¨r Festko¨rperforschung,Heisenbergstr. 1, 70569 Stuttgart, Germany(Dated: December 8, 2008)An antiphased magnetoplasma (MP) mode in a two-dimensional electron gas(2DEG) has been studied by means of inelastic light scattering (ILS) spectroscopy.Unlike the cophased MP mode it is purely quantum excitation which has no classicplasma analogue. It is found that zero momentum degeneracy for the antiphasedand cophased modes predicted by the first-order perturbation approach in terms ofthe e-e interaction is lifted. The zero momentum energy gap is determined by anegative correlation shift of the antiphased mode. This shift, observed experimen-tally and calculated theoretically within the second-order perturbation approach, isproportional to the effective Rydberg constant in a semiconductor material.PACS: 71.35.Cc, 71.30.+h, 73.20.Dx

Super-long life time for 2D cyclotron spin-flip excitons

An experimental technique for the indirect manipulation and detection of electron spins entangled in two-dimensional magnetoexcitons has been developed. The kinetics of the spin relaxation has been investigated. Photoexcited spin-magnetoexcitons were found to exhibit extremely slow relaxation in specific quantum Hall systems, fabricated in high mobility GaAs/AlGaAs structures; namely, the relaxation time reaches values over one hundred microseconds. A qualitative explanation of this spin-relaxation kinetics is presented. Its temperature and magnetic field dependencies are discussed within the available theoretical framework.

Slow spin relaxation in a quantum Hall ferromagnet state

(Received 18 October 2013; revised manuscript received 27 March 2014; published 10 April 2014)Electron spin relaxation in a spin-polarized quantum Hall state is studied. Long spin-relaxation times that areat least an order of magnitude longer than those measured in previous experiments were observed and explainedwithin the spin-exciton relaxation formalism. The absence of any dependence of the spin-relaxation time on theelectron temperature and on the spin-exciton density, and a specific dependence on the magnetic field indicate adefiniterelaxationmechanism—spin-exciton annihilationmediatedbyspin-orbitcouplingandasmoothrandompotential.DOI: 10.1103/PhysRevB.89.161301 PACS number(s): 73

Coherent spin dynamics of different density high mobility two-dimensional electron gas in a GaAs quantum well

We have addressed the dependence of quasi-two-dimensional electron spin dephasing time on the electron gas density in a 17-nm GaAs quantum well using the time-resolved magneto-optical Kerr effect. A superlinear increase in the electron dephasing time with decreasing electron density has been found. The degree of electron spin relaxation anisotropy has been measured and the dependence of spin-orbit splitting on electron gas density has been determined.

Interface D− complexes in a two-dimensional electron system

The excitation spectrum of a two-dimensional electron system in high-quality AlGaAs/GaAs quantum wells has been studied by Raman scattering. New Raman lines due to the excitation of interface D− complexes in which two electrons localized in a quantum well are coupled to a charged impurity at the quantum well interface have been identified. The ground state of the interface D− complexes has been found to change in the transverse magnetic field from spin-singlet to spin-triplet, similar to a change in the ground state of the system of two electrons localized in a harmonic potential.

Barrier D− complexes in a high-mobility two-dimensional electron system

The cyclotron excitation spectrum of selectively doped AlGaAs/GaAs quantum wells with a high (up to 2 × 107 cm2/(V s)) mobility of electrons has been studied by means of the Raman scattering. The lines of the Raman scattering by the excitations of D− complexes, the objects in which two electrons localized in a quantum well are coupled to a charged impurity in a barrier, have been detected and identified. Spin-singlet D− complexes have been shown to exist in the entire range of the electron filling factor, from v → 0 to v = 2, owing to the specificity of the Coulomb interaction in two-dimensional systems. The excitation energies of the singlet D− complexes have been studied as functions of the electron density, quantum well width, and magnetic field.

Rayleigh scattering of light by two-dimensional electrons in a high magnetic field

Resonance Rayleigh scattering of light by a two-dimensional electron system in the ultraquantum limit is investigated. The scattering process under study involves electronic states belonging to the two spin sublevels of the zero Landau level. It is shown that the main contribution to resonance Rayleigh scattering originates from the fluctuations of the random potential in the quantum well hosting the two-dimensional system.

Cyclotron spin-flip mode in the extreme quantum limit

In a two-dimensional electron system, the combined excitation (the cyclotron spin-flip mode) associated with changes in both orbital and spin quantum numbers is investigated. The energy of the cyclotron spin-flip mode is studied as a function of the electron filling factor. Comparative dependences of the decay times of the cyclotron spin-flip mode and the magnetoplasmon are measured. It is shown that, as the filling factor increases from v = 0 or decreases from v = 1, the damping of the cyclotron spin-flip mode increases significantly, while the magnetoplasma mode remains undamped.

Long-Lived Magnetoexcitons and Two-Dimensional Magnetofermionic Condensate in GaAs/AlGaAs Heterostructure

Excitation of long-lived triplet magnetoexcitons in a Hall insulator (filling factor ν = 2) with a high mobility of electrons, at low temperatures, Т < 1 K, enabled to discover a new collective state − magnetofermionic condensate, that interacts coherently with an external electromagnetic field, exhibits superradiant properties and, owing to its low viscosity, spreads over the surface of the two-dimensional structure for macroscopically large distances.

Author Correction: Long-range non-diffusive spin transfer in a Hall insulator

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.