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CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-3433
DTSTART:20141106T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260312T225923Z
LAST-MODIFIED:20141027T151807Z
LOCATION:5310 Chamberlin Hall
SUMMARY:Accurate and efficient simulation of donors in silicon\, R. G.
  Herb Condensed Matter Seminar\, John King Gamble\, Sandia National La
 boratories
DESCRIPTION:For the past sixty years\, researchers have studied the el
 ectronic structure of donors in silicon using the effective mass appro
 ximation\, where electronic states are restricted to the vicinity of s
 ilicon's six conduction band minima. Despite including central cell co
 rrections and valley-orbit coupling\, effective mass theories to date 
 are typically regarded as phenomenological tools\, while more computat
 ionally-intensive atomistic simulations are more trustworthy.<br>
\n<b
 r>
\nHere\, we present a fully internally consistent effective mass th
 eory that includes<br>
\nvalley-orbit coupling and relies upon only a 
 few approximations. Inspired by recent density functional theory calcu
 lations\, we include a tetrahedral central cell correction\, variation
 ally matching experimentally measured energy levels of phosphorous don
 ors in silicon. When imposing internal consistency\, we find both the 
 form of the central cell and the Bloch functions are critically import
 ant to obtaining agreement with experiment.<br>
\n<br>
\nWithin this n
 ew effective mass framework\, we obtain quantitative agreement with th
 e NEMO 3D tight-binding code when calculating the tunnel coupling ener
 gy between two phosphorous donors in silicon\, a critical quantity for
  donor-based quantum information processing. We then use our framework
 \, which is several orders of magnitude faster than comparable atomist
 ic simulations\, to exhaustively enumerate tunnel coupling over a ~30 
 nm cube of donor placements\, about 1.3 million distinct placements. T
 his high-throughput approach enables the identifications of regions wh
 ere the tunnel coupling shows little variation among nearby donor posi
 tions with high probability\, suggesting the feasibility of realistic 
 devices with regular\, controllable properties.<br>
\n<br>
\nThis work
  was supported by the Laboratory Directed Research and Development pro
 gram at Sandia National Laboratories. Sandia National Laboratories is 
 a multi-program laboratory managed and operated by Sandia Corporation\
 , a wholly owned subsidiary of Lockheed Martin Corporation\, for the U
 .S. Department of Energy's National Nuclear Security Administration un
 der contract DE-AC04-94AL85000.<br>
\n
URL:https://www.physics.wisc.edu/events/?id=3433
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