Evidence of breakdown of the spin symmetry in diluted 2D electron gasesP. Giudici1, A. R. Goñi2, P. G. Bolcatto3, C. R. Proetto4, C. Thomsen1, K. Eberl5 and M. Hauser5
1 Institut für Festkörperphysik, Technische Universität Berlin - Hardenbergstr. 36, 10623 Berlin, Germany
2 ICREA Research Professor, Institut de Ciència de Materials de Barcelona, Campus de la UAB - 08193 Bellaterra, Spain
3 Facultad de Ingeniería Química and Facultad de Humanidades y Ciencias, Universidad Nacional del Litoral - 3000 Santa Fe, Argentina
4 Centro Atómico Bariloche and Instituto Balseiro - 8400 S. C. de Bariloche, Río Negro, Argentina
5 MPI für Festkörperforschung - Heisenbergstr. 1, 70569 Stuttgart, Germany
received 20 July 2006; accepted in final form 30 November 2006; published February 2007
published online 1 February 2007
Direct evidence of spin polarisation in dilute two-dimensional electron gases formed in modulation-doped single quantum wells has been obtained from resonant inelastic light scattering. The abrupt enhancement of the exchange-correlation energy of collective intersubband spin and charge excitations observed at very low occupations of the second subband is the signature of the breakdown of the spin symmetry. Calculations of the elementary excitations within the time-dependent local spin-density approximation provide an explanation for the striking behaviour of the different terms of the Coulomb interaction and predict the existence of a ferromagnetic ground state in the very diluted regime.
73.20.Mf - Collective excitations (including excitons, polarons, plasmons and other charge-density excitations).
71.15.Mb - Density functional theory, local density approximation, gradient and other corrections.
78.30.Fs - III-V and II-VI semiconductors.
© Europhysics Letters Association 2007