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SUMMARY:Observation of fractional ac Josephson effect: the signature of Ma
 jorana particles - Prof. Leonid Rokhinson Purdue University
DTSTART:20130709T100000Z
DTEND:20130709T110000Z
UID:TALK46230@talks.cam.ac.uk
CONTACT:Emily Heavens
DESCRIPTION:\nIn 1928 Dirac reconciled quantum mechanics and special relat
 ivity in a set of coupled equations which became the cornerstone of quantu
 m mechanics. Its main prediction that every elementary particle has a comp
 lex conjugate counterpart - an antiparticle - has been confirmed by numero
 us experiments.\nA decade later Majorana showed that Dirac's equation for 
 spin-1/2 particles can be modified to permit real wavefunctions. The compl
 ex conjugate of a real number is the number itself\, which means that such
  particles are their own antiparticles. The most intriguing feature of Maj
 orana particles is that in low dimensions they obey non-Abelian statistics
  and can be used to realize quantum gates that are topologically protected
  from local sources of decoherence. While the search for Majorana fermions
  among elementary particles is still ongoing\, excitations sharing their p
 roperties may emerge in electronic systems. It has been predicted that Maj
 orana excitations may be formed in some unconventional states of matter. I
  will report the observation of the fractional ac Josephson effect in a hy
 brid semiconductor/superconductor InSb/Nb nanowire junction\, a hallmark o
 f topological matter. When the junction is irradiated with rf frequency f 
 at zero external magnetic field\, quantized voltage steps (Shapiro steps) 
 with a height hf/2e are observed\, as is expected for conventional superco
 nductor junctions where the supercurrent is carried by charge-2e Cooper pa
 irs. At high fields the height of the first Shapiro step is doubled to hf/
 e\, suggesting that the supercurrent is carried by charge-e quasiparticles
 . This is a unique signature of Majorana fermions\, elusive particles pred
 icted ca.\n80 years ago.\n
LOCATION:Microelectronics Research Centre (MRC) Seminar Room\, Cavendish L
 aboratory\, Department of Physics
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