Exotic Pressure-Driven Band Gap Widening in Carbon Chain-Filled KFI Zeolite and Its Pathway to High-Pressure Semiconducting Electronics and High-Temperature Superconductivity

TL;DR

This study reveals unusual pressure effects on carbon chains in KFI zeolite, including band gap widening and high-temperature superconductivity, opening new avenues for high-pressure electronics and superconducting materials.

Contribution

It uncovers the re-entrant band gap behavior under pressure and demonstrates synthesis of long cumulene chains with high superconducting transition temperatures within zeolite frameworks.

Findings

Band gap widens with pressure in high-pressure regime.

Cumulene chains exceeding 5,000 atoms synthesized in KFI zeolite.

Superconducting transition temperature reaches ~62 K.

Abstract

Semiconducting devices face persistent challenges in operating at high pressure, as the band theory predicts that materials transition to a more metallic state under compression. However, our findings with carbon chains in KFI substrates reveal a conditional deviation from this norm. We not only witness the transition from polyyne (semiconductor) to cumulene (metal) at medium pressure, but we also observe an unexpected re-entrance of the polyyne at high pressures, where the band gap in the polyyne increases with pressure. In addition, the synthesis of long cumulene chains has posed a longstanding challenge in the quest for high-temperature organic superconductivity. We have identified critical conditions for synthesizing extended cumulene chains within zeolite frameworks, highlighting the interplay between unconventional charge density waves and significant torsions. The KFI zeolite facilitates the formation of carbon chains exceeding 5,000 atoms, in stark contrast to around 100 other zeolites that are limited to ~10 atoms. The cumulene@KFI system demonstrates a superconducting transition temperature reaching ~62 K, surpassing the highest reported values for bulk iron-based superconductors. This interplay between carbon structures and superconductivity not only advances our understanding of charge density waves but also heralds a new era in the study of novel applications