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UID:UW-Physics-Event-2769
DTSTART:20121108T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260420T022049Z
LAST-MODIFIED:20121024T140426Z
LOCATION:5310 Chamberlin
SUMMARY:Observation of fractional ac Josephson effect: the signature o
 f Majorana particles\, R. G. Herb Condensed Matter Seminar\, Leonid Ro
 khinson\, Purdue University
DESCRIPTION:In 1928 Dirac reconciled quantum mechanics and special rel
 ativity in a set of coupled equations which became the cornerstone of 
 quantum mechanics. Its main prediction that every elementary particle 
 has a complex conjugate counterpart - an antiparticle - has been confi
 rmed by numerous experiments. A decade later Majorana showed that Dira
 c's equation for spin-1/2 particles can be modified to permit real wav
 efunctions. The complex conjugate of a real number is the number itsel
 f\, which means that such particles are their own antiparticles. The m
 ost intriguing feature of Majorana particles is that in low dimensions
  they obey non-Abelian statistics and can be used to realize quantum g
 ates that are topologically protected from local sources of decoherenc
 e. While the search for Majorana fermions among elementary particles i
 s still ongoing\, excitations sharing their properties may emerge in e
 lectronic systems. It has been predicted that Majorana excitations may
  be formed in some unconventional states of matter. I will report the 
 observation of the fractional ac Josephson effect in a hybrid semicond
 uctor/superconductor InSb/Nb nanowire junction\, a hallmark of topolog
 ical matter. When the junction is irradiated with rf frequency f at ze
 ro external magnetic field\, quantized voltage steps (Shapiro steps) w
 ith a height hf/2e are observed\, as is expected for conventional supe
 rconductor junctions where the supercurrent is carried by charge-2e Co
 oper pairs. At high fields the height of the first Shapiro step is dou
 bled to hf/e\, suggesting that the supercurrent is carried by charge-e
  quasiparticles. This is a unique signature of Majorana fermions\, elu
 sive particles predicted ca. 80 years ago. 
URL:https://www.physics.wisc.edu/events/?id=2769
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