Reference : UMR8502-CHAQUA-001
Workplace : ORSAY
Date of publication : Wednesday, July 27, 2022
Scientific Responsible name : Charis Quay, Marco Aprili
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
While the ground state of conventional (Bardeen Cooper Schrieffer) superconductors is a spin singlet state of paired electrons (Cooper pairs), triplet superconductivity is expected to arise in systems with superconducting correlations in which non-colinear magnetic fields exist, perhaps most notoriously in magnetic textures. Triplet pairs have recently been predicted to exist in superconductors with Ising (or valley Zeeman) spin-orbit coupling (ISOC), such as the transition metal dichalcogenide NbSe2, due to the non-colinearity between the Ising field, which pins Cooper pair spins out-of-plane, and an applied in-plane magnetic field.
Despite significant efforts and some preliminary evidence, the existence of equal-spin triplet superconductivity remains an unsettled question. We propose a novel approach: coupling directly to the triplet pairs' spin degree of freedom in resonance measurements.
The PhD student will begin with a straightforward continuation of previous work, i.e. the search for predicted spectral signatures of triplet pairs in tunnel measurements such as have been performed in the past. In parallel, we shall perform simulations, fabrication and characterisation of resonators (either superconducting or dielectric) for spin resonance measurements. After tests on better-known systems such as ferromagnetic metals or insulators, the technology thus developed will be used for spin resonance of triplet pairs in superconducting NbSe2. Resonance detection will be either in the microwave regime, or through quantum transport (critical current, kinetic inductance, tunnel conductance…). The PhD student would also be welcome to participate in related projects in the group, notably around superconductivity and the spin-orbit interaction.
M Kuzmanović, T Dvir, D Möckli, S Ilić, JSM Meyer, M Houzet, M Aprili, M Khodas, H Steinberg, CHL Quay, 'Tunneling spectroscopy of few-monolayer NbSe2 in high magnetic field : Ising protection and triplet superconductivity', arXiv:2104.00328.
CHL Quay, Y Chiffaudel, C Strunk and M Aprili, 'Quasiparticle spin resonance and coherence in superconducting aluminium,' Nature Communications 6, 8660 (2015).
The Nanostructures at the Nanosecond timescale (NS2) group has extensive experience in mesoscopic superconductivity, spin-orbit and 2D systems, as well as low-temperature transport and microwave measurements. The LPS is equipped with a transfer station in a glove box, necessary for the fabrication of these 2D devices.
This project is part of an ANR-funded collaboration (TRIPRES) between the LPS, C2N in Palaiseau and PHELIQS in Grenoble, which is coordinated by Charis Quay, Hervé Aubin and Julia Meyer.
Further information is available upon requestion.
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