COLLECTIVE MODES IN A SYMMETRY-BROKEN PHASE - ANTIFERROMAGNETICALLY CORRELATED QUANTUM-WELLS

We investigate the intersubband spin-density-excitation spectrum of a double quantum well in a low-density symmetry-broken phase with interw ell antiferromagnetic, correlations. This spectrum is related to the i ntensity measured in depolarized inelastic light scattering (ILS) expe riments and therefore provides a means of empirically identifying the antiferromagnetic phase. Our computations reveal the existence of two collective modes, a damped Nambu-Goldstone (NG) mode arising from the broken spin symmetry and an undamped optical mode. Since the NG mode c ontains most of the spectral weight, ILS experiments will need to exam ine the low-frequency response for signatures of the antiferromagnetic phase. Copyright (C) 1996 Published by Elsevier Science Ltd.