APS March Meeting 2012
Volume 57, Number 1
Monday–Friday, February 27–March 2 2012;
Boston, Massachusetts
Session Z19: Invited Session: Non-Abelian States in the 1st Excited Landau Level: Experimental Status and Theoretical Outlook
11:15 AM–2:15 PM,
Friday, March 2, 2012
Room: 253AB
Sponsoring
Unit:
DCMP
Chair: Aron Pinczuk, Columbia University
Abstract ID: BAPS.2012.MAR.Z19.1
Abstract: Z19.00001 : Interferometric evidence for non-Abelian quasiparticles at filling factor 5/2
11:15 AM–11:51 AM
Preview Abstract
Abstract
Author:
Robert Willett
(Bell Laboratories, Alcatel-Lucent)
The 5/2 fractional quantum Hall state charge e/4 excitations are proposed to
follow non-Abelian statistics [1]. In edge state interference these purported
non-Abelian quasiparticles should display period e/4 Aharonov-Bohm
oscillations if the interfering quasiparticle encircles an even number of
localized e/4 charges, but suppression of oscillations if an odd number is
encircled [2-3]. To test this, we have performed swept area interference
measurements at 5/2 [4-5]. We observe an alternating pattern of e/4 and e/2
period oscillations in resistance for a large change in the interferometer
area, with the area sweep changing the enclosed localized e/4 quasiparticle
number. This observed aperiodic alternation is consistent with proposed
non-Abelian e/4 properties: the e/4 oscillations occur for encircling an
even number of localized quasiparticles over their aperiodic spatial
distribution, and the lower amplitude e/2 oscillations are observed when
encircling an odd number as the e/4 oscillations are suppressed, allowing
observation of the persistent smaller Abelian e/2 oscillations. Importantly,
adding localized quasiparticles to the encircled area by changing magnetic
field can change the parity of the enclosed quasiparticle number and should
induce interchange of the expressed e/4 and e/2 periods: such interchange is
observed in these measurements.
In further experiments with the goal of understanding specific e/4 edge
propagation properties, a series of interferometers of different sizes have
been tested. The range of device dimensions has allowed measurement of the
e/4 quasiparticle propagation attenuation length, demonstrating that small
interferometric pathlengths are necessary to observe the interference
oscillations. The stability in phase and amplitude of the e/4 oscillations
has been tested with respect to sample dimensions, time, and temperature
using this set of interferometers, and these results will be discussed.
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[1] Moore, G. and Read, N., Nucl. Phys. B360, 362 (1991).
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[2] Stern, A. and Halperin, B. I., Phys. Rev. Lett. 96, 016802-016805
(2006).
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[3] Bonderson, P., Kitaev, A. and Shtengel, K., Phys. Rev. Lett. 96,
016803-016806 (2006).
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[4] Willett, R.L., Pfeiffer, L.N., West, K.W., PNAS 106: 8853-8858 (2009).
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[5] Willett, R.L., Pfeiffer, L.N., West, K.W., PRB 82: 205301 (2010).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.Z19.1