Magnetic field-dependent surface impedance measurement in UTe₂

Microwave spectroscopy offers a sensitive probe of electrodynamics in unconventional superconductors. Recent studies on UTe₂ have revealed an anomalous residual normal-fluid response at low temperature, suggesting the presence of gapless surface states associated with chiral spin-triplet pairing [1]. To further investigate this phenomenon, we develop a seamless high-quality factor copper “flute” cavity, inspired by the cylindrical design of Chakram et al. [2], optimized for low-loss operation under magnetic fields. This platform enables sensitive measurements of the microwave surface impedance of UTe₂ across a broad parameter space encompassing frequency, temperature, and magnetic field. These measurements may shed new light on the normal-fluid dynamics, superfluid stiffness, and the microscopic nature of superconductivity in UTe₂.

[1] Bae, Seokjin, et al. "Anomalous normal fluid response in a chiral superconductor UTe2." Nature communications 12.1 (2021): 2644.

[2] Chakram, Srivatsan, et al. "Seamless high-Q microwave cavities for multimode circuit quantum electrodynamics." Physical review letters 127.10 (2021): 107701.