Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
1998-05-26
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
16 pages, 18 figures. Submitted to Phys. Rev. B
Scientific paper
10.1103/PhysRevB.58.13036
The critical filling factor v_c where Shubnikov-de Haas oscillations become spin split is investigated for a set of GaAs-GaAlAs heterojunctions. Finite temperature magnetoresistance measurements are used to extract the value of v_c at zero temperature. The critically point is where the disorder potential has the same magnitude as the exchange energy, leading to the empirical relationship v_c = g* n t h / 2 m_0. This is valid for all the samples studied, where the density n and single particle lifetime t both vary by more than an order of magnitude and g* the exchange enhanced g-factor has a weak dependence on density. For each sample the spin gap energy shows a linear increase with magnetic field. Experiments in tilted magnetic field show the spin gap is the sum of the bare Zeeman energy and an exchange term. This explains why measurements of the enhanced g-factor from activation energy studies in perpendicular field and the coincidence method in tilted fields have previously disagreed.
Foxon C. T.
Harris Jason
Leadley D. R.
Nicholas Jack R.
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