We use the dynamical structure factors of the quantum Hall states at ν=1/3 and 1/2 in the lowest Landau level to study their excitation spectrum. Using the density matrix renormalization group in combination with the time-dependent variational principle on an infinite cylinder geometry, we extract the low-energy properties. At ν=1/3, a sharp magnetoroton mode and the two-roton continuum are present and the finite-size effects can be understood using the fractional charge of the quasiparticle. At ν=1/2, we find low-energy modes with linear dispersion and the static structure factor s¯(q)∼(qℓ)3 in the limit qℓ→0. The properties of these modes agree quantitatively with the predictions of the composite-fermion theory placed on the infinite cylinder.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics