Observation of pseudogap in SnSe2 atomic layers grown on graphite

TL;DR

This study reports the observation of a pseudogap in atomically thin SnSe2 layers grown on graphite, providing insights into the possible mechanisms of 2D superconductivity in layered materials.

Contribution

It presents the first direct evidence of a pseudogap in 2D SnSe2 layers, advancing understanding of superconductivity in layered transition metal dichalcogenides.

Findings

Pseudogap observed near Fermi level in SnSe2 layers

Pseudogap evolves into a shallow dip at higher temperatures

Provides evidence of pseudogap state in electron-doped 2D SnSe2

Abstract

Superconducting metal dichalcogenides (MDCs) present several similarities to the other layered superconductors like cuprates. The superconductivity in atomically thin MDCs has been demonstrated by recent experiments, however, the investigation of the superconductivity intertwined with other orders are scarce. Investigating the pseudogap in atomic layers of MDCs may help to understand the superconducting mechanism for these true two-dimensional (2D) superconducting systems. Herein we report a pseudogap opening in the tunneling spectra of thin layers of SnSe2 epitaxially grown on highly oriented pyrolytic graphite (HOPG) with scanning tunneling microscopy/spectroscopy (STM/STS). A significant V-shaped pseudogap was observed to open near the Fermi level (EF) in the STS. And at elevated temperatures, the gap gradually evolves to a shallow dip. Our experimental observations provide direct evidence of a pseudogap state in the electron-doped SnSe2 atomic layers on the HOPG surface, which may stimulate further exploration of the mechanism of superconductivity at 2D limit in MDCs.