Coexisting Electronic Smectic Liquid Crystal and Superconductivity in a Si Square-Net Semimetal.

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Electronic nematic and smectic liquid crystals often precede or coexist with unconventional superconductivity.
• Understanding the interplay between these phases is crucial for discovering new superconducting materials.

Purpose of the Study:

• To investigate the presence of charge stripe order in NaAlSi, a material with speculated unconventional superconductivity.
• To resolve the spatial modulation of the superconducting gap amplitude in relation to the observed order.

Main Methods:

• Scanning tunneling microscopy (STM) was employed to observe short-range charge stripe (smectic) order.
• Numerical calculations were performed to elucidate the underlying driving mechanisms.

Main Results:

• Short-range charge stripe order was identified in NaAlSi.
• A clear spatial modulation of the superconducting gap amplitude was resolved, linked to intertwined superconducting and smectic orders.
• Numerical calculations suggest kinetic energy suppression on the Fermi surface as a possible driving mechanism.

Conclusions:

• The study reveals intertwined superconducting and smectic orders in NaAlSi.
• This interplay is driven by specific electronic structures, particularly hole pockets of p-orbital character.
• Findings contribute to understanding unconventional superconductivity mechanisms.