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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-1875
DTSTART:20100805T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260422T092250Z
LAST-MODIFIED:20100803T125039Z
LOCATION:5310 Chamberlin
SUMMARY:Electrical transport techniques to probe the ground state of c
 losely spaced electron-hole bilayer\, R. G. Herb Condensed Matter Semi
 nar\, Mike Lilly\, Sandia National Laboratory
DESCRIPTION:Electron-hole bilayers are expected to make a transition f
 rom a pair of weakly coupled two-dimensional systems to a strongly cou
 pled exciton system as the barrier between the layers is reduced.    S
 everal clear predictions exist for the transport signature of a transi
 tion to an exciton condensate\, but recent experiments find a more com
 plicated situation.  We report both transport and Coulomb drag measure
 ments electron-hole bilayers fabricated using undoped GaAs/AlGaAs doub
 le quantum well heterostructures with gates on the top and bottom of t
 he structure to independently control the electron and hole density.  
 In the drag measurement\, current is driven in the electron layer whil
 e voltage is measured in the hole layer.   Coulomb drag measurements o
 n devices with a 30 nm barrier are consistent with two weakly coupled 
 2D Fermi systems where the drag decreases with temperature.  For a 20 
 nm barrier\, however\, we observe an increase in the drag resistance a
 s the temperature is reduced.  While these results clearly deviate fro
 m Fermi liquid ground states\, there are a number of possibilities for
  the stronger coupling between the layers.  This work has been support
 ed by the Division of Materials Sciences and Engineering\, Office of B
 asic Energy Sciences\, U.S. Department of Energy. Sandia is a multipro
 gram laboratory operated by Sandia Corporation\, a Lockheed Martin Com
 pany\, for the United States Department of Energy under Contract No. D
 E-AC04-94AL85000.
URL:https://www.physics.wisc.edu/events/?id=1875
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