Magnetic and superconducting properties of the heavy-fermion CeCoIn5 epitaxial film probed by nuclear quadrupole resonance

TL;DR

This study reports the first nuclear quadrupole resonance measurements on an epitaxial CeCoIn5 film, revealing that its magnetic and superconducting properties are similar to bulk crystals despite some local electric field variations.

Contribution

It demonstrates the microscopic magnetic and electronic properties of CeCoIn5 thin films using NQR, showing minimal impact on superconductivity from local electric field inhomogeneities.

Findings

NQR spectra show shifts and broadening indicating electric field changes.

Magnetic fluctuations and superconducting pairing remain unaffected.

Nuclear spin-lattice relaxation rate matches bulk crystal values.

Abstract

Since the progress in the fabrication techniques of thin-films of exotic materials such as strongly correlated heavy-fermion compounds, microscopic studies of the magnetic and electronic properties inside the films have been needed. Herein, we report the first observation of 115In nuclear quadrupole resonance (NQR) in an epitaxial film of the heavy-fermion superconductor CeCoIn5, for which the microscopic field gradient within the unit cell as well as magnetic and superconducting properties at zero field are evaluated. We find that the nuclear spin-lattice relaxation rate in the film is in excellent agreement with that of bulk crystals, whereas the NQR spectra show noticeable shifts and significant broadening indicating a change in the electric-field distribution inside the film. The analysis implies a displacement of In layers in the film, which however does not affect the magnetic fluctuations and superconducting pairing. This implies that inhomogeneity of the electronic field gradient in the film sample causes no pair breaking effect.