Pinning, flux flow resistivity and anisotropy of Fe(Se,Te) thin films from microwave measurements through a bitonal dielectric resonator

TL;DR

This study investigates the anisotropic vortex motion and flux flow resistivity in Fe(Se,Te) thin films using microwave measurements, confirming theoretical scaling laws and identifying dominant pinning mechanisms.

Contribution

It provides the first detailed microwave-based analysis of flux flow resistivity and anisotropy in Fe(Se,Te) thin films, validating BGL scaling theory in this context.

Findings

Flux flow resistivity $ ho_{ff}$ matches BGL scaling law.

Low-field mass anisotropy estimated at ~1.8.

Pinning dominated by isotropic point pins.

Abstract

We report on the anisotropy of the vortex motion surface impedance of a \fst thin film grown on a CaF$_2$ substrate. The dependence on the magnetic field intensity up to 1.2 T and direction, both parallel and perpendicular to the sample $c$-axis, was explored at fixed temperature at two distinct frequencies, $\sim16\;$GHz and $\sim27\;$GHz, by means of bitonal dielectric resonator. The free flux flow resistivity $\rho_{ff}$ was obtained by exploiting standard models for the high frequency dynamics, whereas the angle dependence was studied in the framework of the well known and widely used Blatter-Geshkenbein-Larkin (BGL) scaling theory for anistropic superconductors. Excellent agreement with the scaling law prescription by the fluxon flux flow resistivity was obtained. From the scaling analysis, a low-field mass anisotropy $\sim1.8$ was obtained, well within the value ranges reported in literature. The angular dependence of the pinning constant suggests that pinning is dominated by random, isotropic point pins, consistently with critical current density measurements.