Visualizing nematic transition and nanoscale suppression of superconductivity in Fe(Te,Se)

TL;DR

This study uses spectroscopic-imaging STM to explore the electronic nematic transition in Fe(Te,Se), revealing nanoscale nematic regions and their suppression of superconductivity, influenced by local strain and structural inhomogeneity.

Contribution

It provides new insights into nanoscale nematicity and its impact on superconductivity in Fe(Te,Se), highlighting the role of local strain and inhomogeneity.

Findings

Nanoscale regions of electronic nematicity emerge near critical composition.

Superconductivity is strongly suppressed in areas with static nematic order.

Small anisotropic strain can induce localized nematic regions.

Abstract

The interplay of different electronic phases underlies the physics of unconventional superconductors. One of the most intriguing examples is a high-Tc superconductor FeTe1-xSex: it undergoes both a topological transition, linked to the electronic band inversion, and an electronic nematic phase transition, associated with rotation symmetry breaking, around the same critical composition xc where superconducting Tc peaks. At this regime, nematic fluctuations and symmetry-breaking strain could have an enormous impact, but this is yet to be fully explored. Using spectroscopic-imaging scanning tunneling microscopy, we study the electronic nematic transition in FeTe1-xSex as a function of composition. Near xc, we reveal the emergence of electronic nematicity in nanoscale regions. Interestingly, we discover that superconductivity is drastically suppressed in areas where static nematic order is the strongest. By analyzing atomic displacement in STM topographs, we find that small anisotropic strain can give rise to these strongly nematic localized regions. Our experiments reveal a tendency of FeTe1-xSex near x~0.45 to form puddles hosting static nematic order, suggestive of nematic fluctuations pinned by structural inhomogeneity, and demonstrate a pronounced effect of anisotropic strain on superconductivity in this regime.