Session P23: Superconductivity Theory II: p-wave, chiral, and topological

8:00 AM–11:00 AM, Wednesday, February 29, 2012
Room: 255

Sponsoring Unit: DCMP
Chair: Herbert Fotso, Georgetown University

Abstract ID: BAPS.2012.MAR.P23.7

Abstract: P23.00007 : Thermodynamic signatures of half-quantum vortices in $p+ip$ Josephson junction arrays

9:12 AM–9:24 AM

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  Graham Krahn
    (UC Riverside)

  Kirill Shtengel
    (Associate Professor of Physics, UC Riverside)

A very interesting type of excitation in a chiral p-wave superconductor is a half-quantum vortex. As the name suggests, they carry half of a superconducting flux quantum, and are only possible in superconductors with spin-triplet pairing. An astonishing feature of these excitations is the presence of topologically protected Majorana zero modes. Single half-quantum vortices were recently discovered (J. Jang et al, Science \textbf{331}(6014): 186-188) in superconducting mesoscopic rings made of Sr$_2$RuO$_4$, yet to this date they have not been observed in macroscopic samples. We propose a method for detecting half-quantum vortices in Josephson junction arrays, which could host a large number of these vortices. Contrary to a 3D setting, we argue that half-quantum vortices can be energetically preferable in quasi-2D chiral spin-triplet superconductors. As a result, half-quantum vortices rather than full vortices could drive a Berezinskii-Kosterlitz-Thouless transition (which manifests itself as a resistive transition). We propose to look for their signatures by comparing transition temperatures in $p+ip$ Josephson junction arrays in a transverse magnetic field in both unfrustrated and frustrated cases.

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