arXiv subjects

L. V. Kulik

Publications and source records attributed to L. V. Kulik.

13 recordsLinked to original sources

arXiv2025

Resonant Photoluminescence of Quantum Incompressible Liquids

We investigate resonant photoluminescence arising from incompressible quantum liquids formed in two-dimensional electron systems. We demonstrate that, for excitons composed of a photoexcited electron occupying the upper spin sublevel of the zeroth Landau level and a valence-band hole, the influence of disorder potential fluctuations on optical recombination is strongly suppressed, indicating complete screening of the disorder. We identify an optical invariant quantity that is insensitive to excitation energy yet strongly dependent on the electron temperature, serving as a probe of exciton recombination in quantum liquids. Analysis of this quantity reveals that quantum-liquid formation initiates at (n = 1/3) as the electron temperature decreases, consistent with the Laughlin state. Upon further cooling, the range of filling factors exhibiting quantum-liquid behavior expands continuously from (n = 1/3) toward (n = 1/2). Transitions between distinct incompressible quantum-liquid states occur smoothly, without well-defined phase boundaries separating insulating and conducting regimes. Locally, the system retains quantum-liquid characteristics even as bulk transport measurements indicate finite conductivity. Finally, we present a phase diagram delineating the stability region of incompressible quantum liquids relative to conductive phases.

cond-mat.mes-hall↗

arXiv2023

Non-linear optical response of the excited Laughlin liquid

An ensemble of neutral excitations is constructed experimentally in the Laughlin liquid at the electron filling factor 1/3. The excitations are found to induce a nonlinear optical response, manifested as a quadratic dependence of the reflection signal on the excitation power. The reported experimental results indicate that the observed effect is due to the contribution of the coherent anti-Stokes-Stokes scattering of light from the excited Laughlin liquid.

cond-mat.str-el↗

arXiv2019

The Local Incompressibility of Fractional Quantum Hall States at a Filling Factor of 3/2

We studied neutral excitations in a two-dimensional electron system with an orbital momentum $ΔM = 1$ and spin projection over magnetic field axis $ΔS_z = 1$ in the vicinity of a filling factor of 3/2. It is shown that the 3/2 state is a singular point in the filling factor dependence of the spin ordering of the two-dimensional electron system. In the vicinity of $ν=3/2$, a significant increase in the relaxation time ($τ= 13$ $μ\text{s}$) for the excitations to the ground state is exhibited even though the number of vacancies in the lowest energy level is macroscopically large. The decrease of the relaxation rate is related to the spin texture transformation in the ground state induced by spin flips and electron density rearrangement. We claim the 3/2 state is a locally incompressible fractional quantum Hall state.

cond-mat.str-el↗

arXiv2018

Three-particle electron-hole complexes in two-dimensional electron systems

Three-particle complexes consisting of two holes in the completely filled zero electron Landau level and an excited electron in the unoccupied first Landau level are investigated in a quantum Hall insulator. The distinctive features of these three-particle complexes are an electron-hole mass symmetry and the small energy gap of the quantum Hall insulator itself. Theoretical calculations of the trion energy spectrum in a quantizing magnetic field predict that, besides the ground state, trions feature a hierarchy of excited bound states. In agreement with the theoretical simulations, we observe new photoluminescence lines related to the excited trion states. A relatively small energy gap allows the binding of three-particle complexes with magnetoplasma oscillations and formation of plasmarons. The plasmaron properties are investigated experimentally.

cond-mat.str-el↗

arXiv2016

Artificially constructed plasmaron and plasmon-exciton molecule in 2D-metals

Resonant optical excitation was used to create a macroscopic non-equilibrium ensemble of dark excitons with unprecedentedly long lifetime in a two-dimensional (2D) electron system placed in a quantizing magnetic field. Exotic three-particle and four-particle states, plasmarons and plasmon-exciton molecules, coupled with the surrounding electrons through the collective plasma oscillations are engineered. Plasmarons and plasmon-exciton molecules are manifested as new features in the recombination spectra of non-equilibrium systems. Magnetoplasmarons and magnetotrions in a two-dimensional Hall insulator.

cond-mat.mes-hall↗

arXiv2015

Goldstone mode stochastization in 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 $δS\!=\!δS_z \!=\!-1$, the quantum Hall ferromagnet supports a Goldstone spin exciton that changes the spin quantum numbers to $δS\!=\!0$ and $δS_z\!=\!-1$, which corresponds to a coherent spin rotation of the entire electron system to a certain angle. The Goldstone spin exciton decays through a specific relaxation mechanism that is unlike any other collective spin state.

cond-mat.str-el↗

arXiv2015

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.

cond-mat.str-el↗

arXiv2014

Slow spin relaxation in a quantum Hall ferromagnet state

Electron spin relaxation in a spin-polarized quantum Hall state is studied. Long spin relaxation times that are at least an order of magnitude longer than those measured in previous experiments were observed and explained within the spin-exciton relaxation formalism. Absence of any dependence of the spin relaxation time on the electron temperature and on the spin-exciton density, and specific dependence on the magnetic field indicate the definite relaxation mechanism -- spin-exciton annihilation mediated by spin-orbit coupling and smooth random potential.

cond-mat.mes-hall↗

arXiv2013

Spin relaxation in inhomogeneous quantum dot arrays studied by electron spin resonance

Electron states in a inhomogeneous Ge/Si quantum dot array with groups of closely spaced quantum dots were studied by conventional continuous wave ($cw$) ESR and spin-echo methods. We find that the existence of quantum dot groups allows to increase the spin relaxation time in the system. Created structures allow us to change an effective localization radius of electrons by external magnetic field. With the localization radius close to the size of a quantum dot group, we obtain fourfold increasing spin relaxation time $T_1$, as compared to conventional homogeneous quantum dot arrays. This effect is attributed to averaging of local magnetic fields related to nuclear spins $^{29}$Si and stabilization of $S_z$-polarization during electron back-and-forth motion within a quantum dot group.

cond-mat.mes-hall↗

arXiv2010

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.

cond-mat.mes-hall↗

arXiv2008

Cyclotron spin-flip excitations in a ν=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.

cond-mat.mes-hall↗

arXiv2008

Antiphased Cyclotron-Magnetoplasma Mode in a Quantum Hall System

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 classic plasma analogue. It is found that zero momentum degeneracy for the antiphased and cophased modes predicted by the first-order perturbation approach in terms of the {\it e-e} interaction is lifted. The zero momentum energy gap is determined by a negative correlation shift of the antiphased mode. This shift, observed experimentally and calculated theoretically within the second-order perturbation approach, is proportional to the effective Rydberg constant in a semiconductor material.

cond-mat.mes-hall↗

arXiv2008

The 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 ($ν=2,4$) 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.

cond-mat.mes-hall↗