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SUMMARY:Quantised charge pumping in a perpendicular magnetic field - Mr Sa
 m Wright (Semiconductor Physics Group\, Cambridge)
DTSTART:20100524T131500Z
DTEND:20100524T141500Z
UID:TALK24776@talks.cam.ac.uk
CONTACT:afw24
DESCRIPTION:Quantised charge transport devices have been studied over the 
 last two decades\, mainly for their promising application as standards for
  electrical current in the field of quantum metrology. The ability to tran
 sport a precise number of electrons (holes) from a source to a drain at a 
 well-known frequency allows for the redefinition of the SI base unit for c
 urrent\, the ampere\, in terms of a clock cycle and the elementary charge\
 ; a fundamental invariant of nature (or so we have good reason to believe)
 .\n\nFor a practical standard based on quantised charge transport\, it is 
 necessary for the magnitude of generated current to be greater than a nano
 ampere with an accuracy of one part in ten billion. These goals have not y
 et been reached simultaneously.\n\nI will\, in a roughly chronological ord
 er\, list the different types of quantised charge transport devices that h
 ave been developed since the early '90s. In each case\, I will highlight t
 heir specific strengths and weaknesses in the race to redefine the ampere.
  I will then discuss in detail the high-frequency fixed-barrier GaAs/AlGaA
 s electron pump\, first developed within our group several years ago. I wi
 ll present results from our recent measurements using a perpendicular magn
 etic field where we demonstrate the most accurate source of quantised curr
 ent above 50pA. I will show that our pumps are parallelisable\, increasing
  the output current without significant loss of quantisation. I will also 
 present experimental data and results from simulations by Dr Adam Thorn wi
 th the aim to argue the case that our electron pump devices may prove to b
 e extremely useful tools for probing fundamental charge interactions in dy
 namic quantum dot potentials.
LOCATION:Mott Seminar Room
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