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UID:UW-Physics-Event-2972
DTSTART:20130226T160000Z
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DTSTAMP:20260420T020602Z
LAST-MODIFIED:20130218T205804Z
LOCATION:5280 Chamberlin Hall
SUMMARY:Gate control of single electron spin in III-V semiconductor qu
 antum dots: Anisotropy effects \, R. G. Herb Condensed Matter Seminar\
 , Sanjay Prabhakar\, Wilfrid Laurier University
DESCRIPTION:Among recent proposals for next-generation non-charge-base
 d logic is the notion that a single electron can be trapped and its sp
 in can be manipulated through the application of gate potentials.  In 
 the first part of my talk\, I present numerical simulations of such sp
 ins in single-electron devices for realistic asymmetric confining pote
 ntials in two-dimensional electrostatically confined quantum dots. Usi
 ng both analytical and numerical techniques\, I show that breaking the
  in-plane rotational symmetry of the confining potential leads to a si
 gnificant effect on the tunability of the g- factor and on the spin-fl
 ip rate mediated by phonon with applied gate potentials. In particular
 \, anisotropy either extends the range of the tunability of the g-fact
 or and spin-hot spot to larger quantum dots or viceversa. For example\
 , anisotropy reduces the tunability of the g-factor and spin hot spot 
 to smaller quantum dots radius as well as to smaller magnetic fields i
 f we keep the area of the symmetric and asymmetric quantum dots same. 
 It is well known that the cusp-like structure due to accidental degene
 racy in the phonon mediated spin-flip rate can be seen only for the ca
 se of pure Rashba spin-orbit coupling in symmetric quantum dots. I pre
 sent new analytical and numerical results which show that the cusp-lik
 e structure can be seen for pure Dresselhaus spin-orbit coupling case 
 in asymmetric quantum dots.  <br>
\n<br>
\nIn the second part of my ta
 lk\, I investigate the geometric phase induced on the spin states duri
 ng the adiabatic movement of the III-V semiconductor quantum dots in t
 he plane of two-dimensional electron gas under the influence of applie
 d gate potential along the lateral direction. Here\, I present the spi
 n-flip probabilities during the adiabatic evolution in the presence of
  the Rashba and the Dresselhaus linear spin-orbit interactions. I use 
 the Feynman disentanglement technique to determine the non-Abelian Ber
 ry phase and find exact analytical expressions for three special cases
 : (a) the pure Rashba spin-orbit coupling\, (b) the pure Dresselhause 
 linear spin-orbit coupling\, and (c) the mixture of the Rashba and Dre
 sselhaus spin-orbit couplings with equal strength. For a mixture of th
 e Rashba and the Dresselhaus spin-orbit couplings with unequal strengt
 hs\, I obtain numerical results by solving the Riccati equation origin
 ating from the disentangling procedure. I find that the spin-flip prob
 ability in the presence of the mixed spin-orbit couplings is generally
  larger than those for the pure Rashba case and for the pure Dresselha
 us case\, and that the complete spin-flip takes place only when the Ra
 shba and the Dresselhaus spin-orbit couplings are mixed symmetrically.
 <br>
\n<br>
\nReferences:  <br>
\n<br>
\nGate control of a quantum dot
  single-electron spin in realistic confining potentials: Anisotropy ef
 fects\; Sanjay Prabhakar and James Raynolds\, phys. Rev. B 79\, 195307
  (2009).  <br>
\n<br>
\nManipulation of single electron spin in a GaAs
  quantum dot through the application of geometric phases: The Feynman 
 disentangling technique\; Sanjay Prabhakar\, James E Raynolds\, Akira 
 Inomata and Roderick Melnik\, Phys. Rev. B 82\, 195306 (2010).  <br>
\
 n<br>
\nManipulation of the Lande g-factor in InAs quantum dots throug
 h the application of anisotropic gate potentials\; Sanjay Prabhakar\, 
 James E Raynolds and Roderick Melnik\, Phys. Rev. B 84\, 155208 (2011)
 .  <br>
\n<br>
\nThe influence of anisotropic gate potentials on the p
 honon induced spin-flip rate in GaAs quantum dots\; Sanjay Prabhakar\,
  Roderick Melnik and Luis L Bonilla\, Applied Physics Letters 100\, 02
 3108 (2012). <br>
\n
URL:https://www.physics.wisc.edu/events/?id=2972
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