Superconducting order parameter domains in Sr2RuO4 probed by Josephson interferometry
Kidwingira, Francoise
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https://hdl.handle.net/2142/31446
Description
Title
Superconducting order parameter domains in Sr2RuO4 probed by Josephson interferometry
Author(s)
Kidwingira, Francoise
Issue Date
2007
Doctoral Committee Chair(s)
Van Harlingen, Dale J.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
chiral domains
strontium ruthenate
Superconductivity
Language
en
Abstract
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.
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