Superconducting order parameter domains in Sr2RuO4 probed by Josephson interferometry

There is evidence for degenerate chiral order parameters of px±ipy symmetry in the superconducting ruthenate Sr2RuO4 which can lead to the presence of chiral order parameter domains in the material. We study bi-metallic Josephson junctions made of Sr2RuO4 and a conventional superconductor. Their critical current modulations in an applied magnetic field carry information about the phase of the order parameter of the ruthenate. In these junctions, we observe multiple phase interference in a single tunneling direction which indicates the presence of order parameter domains. The domain structure creates in some samples a striking qualitative difference between the magnetic field modulations of the critical current of junctions fabricated on orthogonal faces of a Sr2RuO4 single crystal. Transitions between the chiral states of a domain or motion of domain walls separating them generates telegraph noise in the critical current as a function of either magnetic field or time, and is responsible for hysteresis observed in field sweeps of the critical current. Cooling the junctions in a magnetic field lifts the degeneracy between the two types of domains. The increased probability of one chirality over the other translates into an enhanced critical current for the junctions. The presence of such domains confirms the suspected p-wave spin triplet and complex nature of the superconducting pairing state in Sr2RuO4, making it the superconducting analog of the A-phase of superfluid 3He.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2012

Author dc:creator

• Kidwingira, Francoise

Contributors dc:contributor

• Van Harlingen, Dale J.

• chiral domains
• strontium ruthenate
• Superconductivity

Statement dc:rights

• ©2007 Francoise Kidwingira

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/31446

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/31446