L. V. Kulik

Cyclotron spin-flip mode as the lowest-energy excitation of unpolarized integer quantum Hall states

The cyclotron spin-flip modes of spin unpolarized integer quantum Hall states (ν=2,4,6) have been studied with inelastic light scattering. The energy of these modes is significantly smaller compared to the bare cyclotron gap. Second-order exchange corrections are held responsible for a negative energy contribution and render these modes the lowest-energy excitations of unpolarized integer quantum Hall states.

Dielectric enhancement of magnetoexcitons in surface quantum wells

Magnetoexcitons in InGaAs/GaAs surface quantum wells in a quantizing magnetic field are investigated theoretically and experimentally. Dielectric enhancement of an exciton with decreasing thickness of the barrier layer is demonstrated, and the dependence of the effect on the strength of the magnetic field is analyzed for the 1s and 2s states.

Extra Spin-Wave Mode in Quantum Hall Systems: Beyond the Skyrmion Limit

We report on the observation of a new spin mode in a quantum Hall system in the vicinity of odd electron filling factors under experimental conditions excluding the possibility of Skyrmion excitations. The new mode having presumably zero energy at odd filling factors emerges at small deviations from odd filling factors and couples to the spin exciton. The existence of an extra spin mode assumes a nontrivial magnetic order at partial fillings of Landau levels surrounding quantum Hall ferromagnets other then the Skyrmion crystal.

Cyclotron spin-flip excitations in a nu = 1/3 quantum Hall ferromagnet.

Inelastic light scattering spectroscopy around the ν =1/3 filling discloses a novel type of cyclotron spin-flip excitation in a quantum Hall system in addition to the excitations previously studied. The excitation energy of the observed mode follows qualitatively the degree of electron spin polarization, reaching a maximum value at ν =1/3 and thus characterizing it as a ν =1/3 ferromagnet eigenmode. Its absolute energy substantially exceeds the theoretical prediction obtained within the renowned single-mode approximation. Double-exciton corrections neglected utilizing the single-mode approach are evaluated within the framework of the excitonic representation and are inferred to be responsible for the observed effect.

Effect of interparticle interactions on radiative lifetime of photoexcited electron-hole system in GaAs quantum wells

The paper reports on an investigation of changes in the photoluminescence linewidth and lifetime of excitons and electron-hole plasma over a wide range of densities between 3×107 and 3×1012 cm−2 at a temperature of 77 K in GaAs/AlGaAs quantum wells. The roles played by thermal ionization of excitons at low densities of nonequilibrium carriers, exciton-exciton and exciton-electron collisions, and ionization of excitons at high pumping power densities have been studied.

Goldstone mode stochastization in a quantum Hall ferromagnet

Experimental and theoretical studies of the coherent spin dynamics of two-dimensional GaAs/AlGaAs electron gas were performed. The system in the quantum Hall ferromagnet state exhibits a spin relaxation mechanism that is determined by many-particle Coulomb interactions. In addition to the spin exciton with changes in the spin quantum numbers of

Cyclotron spin-wave in the 2D electron system

\ensuremath{\delta}S=\ensuremath{\delta}{S}_{z}=\ensuremath{-}1

Long-range non-diffusive spin transfer in a Hall insulator

, the quantum Hall ferromagnet supports a Goldstone spin exciton that changes the spin quantum numbers to

Cyclotron spin-flip excitations in the 2D-electron system

\ensuremath{\delta}S=0

Intersubband collective excitations in a quasi-two-dimensional electron system in external magnetic field

and