Screening Breakdown on the Route toward the Metal-Insulator Transition in Modulation Doped Si/ SiGe Quantum Wells
Exploiting the spin resonance of a two-dimensional (2D) electron in SiGe/Si quantum wells, we determine the carrier density dependence of the magnetic susceptibility. Assuming weak interaction, we evaluate the density of states at the Fermi level, D(E{sub F}) , and the screening wave vector, q{sub TF} . Instead of the constant values of an ideal 2D system, we observe a gradual decrease towards the band edge. Calculating the mobility from q{sub TF} yields good agreement with experimental values justifying the approach. The decrease in D(E{sub F}) is explained by potential fluctuations which lead to tail states that make screening less efficient and, in a positive feedback, cause an increase of the potential fluctuations.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40277014
- Journal Information:
- Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 2 Vol. 87; ISSN 0031-9007
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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