BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-2972
DTSTART:20130226T160000Z
DURATION:PT1H0M0S
DTSTAMP:20240328T183259Z
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.
\n
\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.
\n
\nReferences:
\n
\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).
\n
\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).
\
n
\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)
.
\n
\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).
\n
URL:https://www.physics.wisc.edu/events/?id=2972
END:VEVENT
END:VCALENDAR