Search for Soft-Mode Instabilities in the Quantum Hall Effect at ν = 2
Abstract
Recently there has been much interest in quantum phase transitions in the quantum hall state of filling factor ν = 2. In single 2D layers, according to Hartree-Fock (HF) calculations, the lowest energy spin-density excitation develops a roton minimum at finite wave vector that softens down to zero energy with increasing interaction strength rs [1]. At higher rs and small Zeeman splitting, which is the case in GaAs heterostructures, the system is predicted to change from unpolarized and translationally invariant to a density-wave state [2]. We report inelastic light scattering measurements of both dispersive and density of states critical point modes from the ν = 2 state with rs > 1. Our results indicate that the roton minimum softens more slowly that predicted by HF. Also, we find that additional nondispersive excitations, with dramatic magnetic field and temperature dependences, appear for rs > 2. [1] M.A. Eriksson et al., Phys. Rev. Let. 82, 2163 (1999) [2] G. Murthy, Phys. Rev. Let. 85, 1954 (2000)
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2001
- Bibcode:
- 2001APS..MARS30013H