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Events on Monday, October 1st, 2012

Special Seminar
Tunneling spectroscopy of many-body effects in a two-dimensional electron gas of near-surface delta-doped layer
Time: 11:30 am
Place: 5310 Chamberlin
Speaker: Sergey Dizhur, Institute of Radioengineering & Electronics, Russian Academy of Science
Abstract: The Al/delta-GaAs tunnel junctions with different subbands spectra in the 2D electron system (2DES) of delta-layer were studied. In each of the junctions subband energies Ei in 2DES can be changed by the diamagnetic shift or by the persistent tunnelling photoconductivity (PTPC) effect. The change of tunnelling conductance at the LO-phonon emission threshold was investigated. The negative change of conductance (electron reflection) was observed for tunnelling in two subband (empty E1 and occupied E0), when intersubband LO-phonon emission into 2DES was possible. The crossover of the zero point in conductance change was found when the energy difference E1F between E1 and the Fermi level EF in 2DES becomes more then LO-phonon energy. In the case the usual inelastic LO-phonon-assisted processes dominate and the new (inelastic) channel is added to the elastic one (positive change).

The obtained results show that the reflection of electrons is related to a new subband being involved in the tunneling process and to the emission of LO-phonons under electron transitions from this subband to the ground state in the 2DES region.
Host: McDermott
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Plasma Physics (Physics/ECE/NE 922) Seminar
Neutronics of ARIES and ITER: Progress and Challenges
Time: 12:00 pm
Place: 1310 Sterling Hall
Speaker: Laila El-Guebaly, University of Wisconsin-Madison
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