Neutral collective modes in spin-polarized fractional quantum Hall states at filling factors 1/3, 2/5, 3/7, and 4/9

Article

关键词: FILLED LANDAU-LEVEL;    COMPOSITE FERMIONS;    MONOPOLE HARMONICS;    EXCITATIONS;    TRANSITION;    SPECTRUM;    FLUID;   

DOI  :  10.1103/PhysRevB.90.155310

来源: SCIE

【 摘 要 】

We determine the lowest and higher order collective modes in both spin-conserving and spin-reversed sectors by calculating the energy differences of appropriate linear combinations of different levels of the excitons of the composite fermions and the fully spin-polarized ground states at filling factors nu = 1/3, 2/5, 3/7, and 4/9. Apart from providing a detailed study of previously reported modes that have also been observed in the experiments, we predict additional higher energy modes at different filling factors. The lowest and the next higher spin-conserving modes have equal number of magnetorotons and the number is the same as the number of filled effective Landau-like levels of composite fermions. The higher energy modes at nu = 1/3 merge with the lowest mode at long wavelengths. The spin-conserving modes do not merge at other filling factors. Apart from showing a zero-energy spin-wave mode at zero momentum, thanks to Larmor's theorem, the lowest spin-reversed modes at the ferromagnetic ground states of nu = 2/5, 3/7, and 4/9 display one or more spin rotons at negative energies, signaling unstable fully polarized ground states at sufficiently small Zeeman energies. The high-energy spin-reversed modes also have spin rotons but at positive energies. The energies of these excitations depend on the finite width of the quantum well as the Coulomb interaction gets screened. We perform a finite thickness correction to the Coulomb interaction by the standard method of local density approximation and use it to calculate the critical energies such as rotons and long- and short-wavelength modes, which are detectable in inelastic light scattering experiments.

【 授权许可】

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