Coexisting electronic smectic liquid crystal and superconductivity in a Si square-net semimetal

TL;DR

This paper reports the discovery of coexisting smectic charge order and superconductivity in NaAlSi, revealing intertwined electronic phases and providing insights into their possible unconventional origin through microscopy and theoretical analysis.

Contribution

It presents the first observation of smectic charge order coexisting with superconductivity in a Si square-net semimetal, supported by microscopy and numerical calculations.

Findings

Observation of short-range charge stripe order in NaAlSi

Detection of spatial modulation of the superconducting gap

Numerical insights into the suppression of kinetic energy as a driving mechanism

Abstract

Electronic nematic and smectic liquid crystals are spontaneous symmetry-breaking phases that are seen to precede or coexist with enigmatic unconventional superconducting states in multiple classes of materials. In this Letter we describe scanning tunneling microscopy observations of a short ranged charge stripe (smectic) order in NaAlSi, whose superconductivity is speculated to have an unconventional origin. As well as this we resolve a clear spatial modulation of the superconducting gap amplitude, which arises due to the intertwined superconducting and smectic orders. Numerical calculations help to understand the possible driving mechanism as a suppression of kinetic energy on the Fermi surface formed in part by two large, flat-topped hole pockets of p-orbital character.