Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 62: Superconductivity: Properties, Electronic Structure, Order Parameter
TT 62.11: Talk
Thursday, March 14, 2013, 18:00–18:15, H19
Temperature dependence of band gaps in semiconductors: electron-phonon interaction — •Reinhard K. Kremer1, M. Cardona1, R. Lauck1, J. Bhosale2, A. K. Ramdas2, A. Burger3, A. Muñoz4, and A. H. Romero5 — 1MPI for Solid State Research, Stuttgart, Germany — 2Physics Dep., Purdue University, West Lafayette, IN — 3Fisk University, Dep. of Life and Physical Sciences, Nashville, TN, USA — 4MALTA Consolider Team, Dep. de Física Fundamental II, and Instituto de Materiales y Nanotecnología, Universidad de La Laguna, La Laguna, Tenerife, Spain — 5CINVESTAV, Dep. de Materiales, Unidad Querétaro, Querétaro, Mexico and MPI für Mikrostrukturphysik, Weinberg 2, Halle, Germany
We investigate the temperature dependence of the energy gap of several semiconductors with chalcopyrite structure and re-examine literature data and analyze own high-resolution reflectivity spectra in view of our new ab initio calculations of their phonon properties. This analysis leads us to distinguish between materials with d-electrons in the valence band (e.g. CuGaS2, AgGaS2) and those without d-electrons (e.g. ZnSnAs2). The former exhibit a rather peculiar non-monotonic temperature dependence of the energy gap which, so far, has resisted cogent theoretical description. We demonstrate it can well be fitted by including two Bose-Einstein oscillators with weights of opposite sign leading to an increase at low-T and a decrease at higher T’s. We find that the energy of the former correlates well with characteristic peaks in the phonon density of states associated with low-energy vibrations of the d-electron constituents.