Crystallographic dependent transport properties and oxygen issue in superconducting LiTi2O4 thin films

TL;DR

This study investigates how the crystallographic orientation affects transport properties in LiTi2O4 thin films and finds oxygen vacancies exist but have minimal impact on superconductivity.

Contribution

It provides a systematic analysis of orientation-dependent transport and reveals oxygen vacancies' limited effect on superconductivity in LiTi2O4 films.

Findings

Transport properties depend on crystallographic orientation.

Oxygen vacancies are present but do not significantly alter Tc.

AMR shows twofold symmetry indicating anisotropic scattering.

Abstract

A systematic study is performed on the spinel oxide, i.e. LiTi2O4 thin films oriented along [111]-, [110]-, and [001]-directions, to reveal the crystallographic dependence of transport properties. With decreasing temperature, the LiTi2O4 displays roughly identical onset temperatures of twofold symmetry of in-plane angular dependent magnetoresistivity (AMR) (at ~ 100 K), crossover from negative- to positive- magnetoresistance (at ~ 50 K), and coherence length in the superconducting state. While, the twofold symmetry in AMR itself suggests anisotropic electron scattering. The superconducting transition temperature (Tc) seems insensitive to the lattice parameter. Moreover, the spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) discloses that oxygen vacancies exist in the LiTi2O4 films. These oxygen vacancies cause the change of lattice but show little influence on superconductivity, differing from high-Tc cuprates where subtle variation of oxygen way lead to a significant change in superconductivity.