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Abstract:
The temperature dependence of the electronic states and energy gaps of
semiconductors is an old but still important experimental and
theoretical topic. Remarkably, extant results do not clarify the
asymptotic T --> 0 behavior. Recent breakthroughs in the spectroscopy
of enriched Si-28 allow us to measure changes in the band gap over the
liquid He-4 temperature range with an astounding precision of one part
in 10(8), revealing a T4.0+/-0.2 decrease with increasing T. This is in
excellent agreement with a theoretical argument predicting an exponent
of 4. This power law should apply, in the low temperature limit, to the
temperature dependence of the energies of all electronic states in
semiconductors and insulators.
