Observation of novel gapped phases in potassium doped single layer p-terphenyl on Au (111)

TL;DR

This study uses STM/STS to investigate potassium-doped single-layer p-terphenyl on Au (111), revealing novel gapped phases that challenge previous superconductivity claims and offering new avenues for 2D hydrocarbon research.

Contribution

It provides direct microscopic evidence of gapped phases in K-doped p-terphenyl and questions the superconductivity interpretation in prior studies.

Findings

Observation of multiple ordered phases with distinct electronic properties.

Detection of a stable 11 meV energy gap below 50 K.

The gap does not respond to magnetic fields up to 11 Tesla.

Abstract

Recently, superconductivity in potassium (K) doped p-terphenyl (C18H14) has been suggested by the possible observation of the Meissner effect and subsequent photoemission spectroscopy measurements, but the detailed lattice structure and more-direct evidence are still lacking. Here we report a low temperature scanning tunneling microscopy/spectroscopy (STM/STS) study on K-doped single layer p-terphenyl films grown on Au (111). We observe several ordered phases with different morphologies and electronic behaviors, in two of which a sharp and symmetric low-energy gap of about 11 meV opens below 50 K. In particular, the gap shows no obvious response to a magnetic field up to 11 Tesla, which would caution against superconductivity as an interpretation in previous reports of K-doped p-terphenyl materials. Such gapped phases are rarely (if ever) observed in single layer hydrocarbon molecular crystals. Our work also paves the way for fabricating doped two-dimensional (2D) hydrocarbon materials, which will provide a platform to search for novel emergent phenomena.