We present a complete investigation of the collective excitations in quantum wells subject to in-plane magnetic fields B, based on the random phase approximation and self-consistently calculated ground states in the Hartree approximation. We find that, for a symmetric quantum well of width w, high in-plane B fields (lB≪w) can, besides the usual optical intrasubband plasmons (OP's), give rise to an additional branch of undamped acoustic plasmons (AP's), which does not exist in a single well without B. In low B fields (lB≪w), the magnetic-field broken symmetry of electron wave functions causes an anticrossing feature of the plasmon dispersions even in the symmetric well. In intermediate B fields (lB≪w), an unusual anisotropy effect occurs: the number of the plasmon branches depends on the angle between the magnetic field and the in-plane plasmon wave vector q. For B∥q, there exist two branches of plasmons (OP's and AP's), whereas only one (OP) exists for B⊥q.
|Number of pages||10|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 15 Feb 2002|