Study of superconductivity in quantum materials using controlled disorder
Date
2024-12
Authors
Ghimire, Sunil
Major Professor
Advisor
Prozorov, Ruslan RP
Tanatar, Makariy
Orth, Peter
Wetstein, Matthew
Zaikina, Julia
Committee Member
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Abstract
Understanding superconductivity in quantum materials requires tuning the system with several
tuning parameters like pressure, magnetic field, chemical doping, and innovative probing techniques,
among which controlled disorder, such as electron and proton irradiation, stands out. In
particular, for unconventional superconductors whose superconductivity appears near the different
types of long-range order like magnetism and charge order, the two phases can be tuned using controlled
disorder, allowing for a better understanding of these existing phases. Moreover, controlled
disorder can be used to study the vortex properties of type-II superconductors by tuning the defect
concentration inside the sample.
In this work, we utilized London penetration depth measurement to study the bulk superconductivity
of topological superconductor candidates: 2M-WS2 and LaNiGa2. In addition, we
studied their response to non-magnetic disorder to understand superconducting order parameter
and pairing states. Similarly, we studied the superconducting properties of ferromagnetic superconductor,
EuFe2(As1−xPx)2. By doing electron irradiation, we studied the superconducting state
in both ferromagnetic and paramagnetic backgrounds. Then, we applied the electron irradiation
to intentionally induce point defects in Ca3Rh4Sn13 and measured the Campbell length at high
frequencies. We observed the disorder-induced peak effect, which is static, by frequency-dependent
measurements. Finally, we experimentally verified the theoretically predicted non-monotonic relaxation
of Campbell length due to creep-enhanced vortex creeping by measuring the Campbell
relaxation, which is not detected in conventional magnetic measurement.
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dissertation