arXiv subjects

A. Pinczuk

Publications and source records attributed to A. Pinczuk.

25 records · Page 2Linked to original sources

arXiv2003

Light Scattering by Low Lying Quasiparticle Excitations in the Fractional Quantum Hall Regime

Low lying excitations of electron liquids in the fractional quantum Hall (FQH) regime are studied by resonant inelastic light scattering methods. We present here results from charge and spin excitations of FQH states in the lowest spin-split Landau levels that are of current interest. In the range of filling factors $2/5 \geq ν\geq 1/3$, we find evidence that low energy quasiparticle excitations can be interpreted with spin-split composite fermion quasi-Landau levels. At FQH states around $ν=3/2$, we find well-defined excitations at 4/3 and 8/5 that are consistent with a spin-unpolarized population of quasi-Landau levels.

cond-mat.mes-hall↗

arXiv2003

Resonant Enhancement of Inelastic Light Scattering in the Fractional Quantum Hall Regime at $ν=1/3$

Strong resonant enhancements of inelastic light scattering from the long wavelength inter-Landau level magnetoplasmon and the intra-Landau level spin wave excitations are seen for the fractional quantum Hall state at $ν= 1/3$. The energies of the sharp peaks (FWHM $\lesssim 0.2meV$) in the profiles of resonant enhancement of inelastic light scattering intensities coincide with the energies of photoluminescence bands assigned to negatively charged exciton recombination. To interpret the observed enhancement profiles, we propose three-step light scattering mechanisms in which the intermediate resonant transitions are to states with charged excitonic excitations.

cond-mat.mes-hall↗

arXiv2003

Light scattering observations of spin reversal excitations in the fractional quantum Hall regime

Resonant inelastic light scattering experiments access the low lying excitations of electron liquids in the fractional quantum Hall regime in the range $2/5 \geq ν\geq 1/3$. Modes associated with changes in the charge and spin degrees of freedom are measured. Spectra of spin reversed excitations at filling factor $ν\gtrsim 1/3$ and at $ν\lesssim 2/5$ identify a structure of lowest spin-split Landau levels of composite fermions that is similar to that of electrons. Observations of spin wave excitations enable determinations of energies required to reverse spin. The spin reversal energies obtained from the spectra illustrate the significant residual interactions of composite fermions. At $ν= 1/3$ energies of spin reversal modes are larger but relatively close to spin conserving excitations that are linked to activated transport. Predictions of composite fermion theory are in good quantitative agreement with experimental results.

cond-mat.mes-hall↗

arXiv2003

Crossover and Coexistence of Quasiparticle Excitations in the Fractional Quantum Hall Regime at $ν\leq 1/3$

New low-lying excitations are observed by inelastic light scattering at filling factors $ν=p/(ϕp \pm 1)$ of the fractional quantum Hall regime with $ϕ=4$. Coexisting with these modes throughout the range $ν\leq 1/3$ are $ϕ=2$ excitations seen at 1/3. Both $ϕ=2$ and $ϕ=4$ excitations have distinct behaviors with temperature and filling factor. The abrupt first appearance of the new modes in the low energy excitation spectrum at $ν\lesssim 1/3$ suggests a marked change in the quantum ground state on crossing the $ϕ=2 \to ϕ=4$ boundary at $ν= 1/3$.

cond-mat.mes-hall↗

arXiv2002

Evidence of Landau levels and interactions in low-lying excitations of composite fermions at 1/3 <= ν<= 2/5

Excitation modes in the range $2/5 \geq ν\geq 1/3$ of the fractional quantum Hall regime are observed by resonant inelastic light scattering. Spectra of spin reversed excitations suggest a structure of lowest spin-split Landau levels of composite fermions that is similar to that of electrons. Spin-flip energies determined from spectra reveal significant composite fermion interactions. The filling factor dependence of mode energies display an abrupt change in the middle of the range when there is partial population of a composite fermion level.

cond-mat.mes-hall↗

arXiv1999

Inelastic Light Scattering by Gap Excitations of Fractional Quantum Hall States at 1/3 <= ν<= 2/3

We report observations of collective gap excitations of the fractional quantum Hall (FQH) states at filling factors ν=p/(2p+1) (p=integer), for 1/3 <= ν<= 2/3, by inelastic light scattering. The collective gap energies at ν= 1/3, 2/5 and 3/7 show a drastic decrease as the value ν=1/2 is approached. These energies and the one at ν=3/5 display the linear scaling with (e^2/εl_o)/|2p+1| that is characteristic of composite fermions in Chern-Simons gauge fields. In a narrow range of νcentered at 1/2, where the FQH gaps collapse, we observe a new excitation mode which exists only at temperatures below 150 mK.

cond-mat.mes-hall↗

arXiv1998

Observation of Collective Excitations of the Dilute 2D Electron System

We report inelastic light scattering measurements of dispersive spin and charge density excitations in dilute 2D electron systems reaching densities less than 10^{10} cm^{-2}. In the quantum Hall state at nu=2, roton critical points in the spin inter--Landau level mode show a pronounced softening as r_s is increased. Instead of a soft mode instability predicted by Hartree--Fock calculations for r_s ~ 3.3, we find evidence of multiple rotons in the dispersion of the softening spin excitations. Extrapolation of the data indicates the possibility of an instability for r_s >~ 11.

cond-mat.mes-hall↗