Epitaxial growth of hexagonal tungsten bronze CsxWO3 films in superconducting phase region exceeding bulk limit

TL;DR

This paper demonstrates the epitaxial growth of superconducting CsxWO3 films with compositions exceeding bulk limits, revealing a hidden superconducting phase accessible through epitaxial synthesis.

Contribution

It introduces a method to synthesize superconducting CsxWO3 films beyond bulk compositional limits, expanding understanding of its phase diagram.

Findings

Superconductivity observed in films with x=0.11, below bulk stability.

Strong correlation between Tc and c-axis length.

Epitaxial synthesis enables access to hidden superconducting phases.

Abstract

We report epitaxial synthesis of superconducting CsxWO3 (x = 0.11, 0.20, 0.31) films on Y-stabilized ZrO2 (111) substrates. The hexagonal crystal structure was verified not only for composition within the stable region of bulk (x = 0.20, 0.31), but also for the out-of-range composition (x = 0.11). The onset of superconducting transition temperature (TC) was recorded 5.8 K for x = 0.11. We found strong correlation between TC and c-axis length, irrespective of the Cs content. The results indicate that hidden superconducting phase region of hexagonal tungsten bronze is accessible by using epitaxial synthesis of lightly doped films.