Momentum-resolved electronic structures and strong electronic correlations in graphene-like nitride superconductors

TL;DR

This study presents the first momentum-resolved electronic band structures of high-quality TiN films, revealing strong electronic correlations that could influence their quantum properties and applications.

Contribution

It provides the first high-resolution electronic band structures of TiN films and quantifies their strong Coulomb interactions using advanced spectroscopic techniques.

Findings

Coulomb interaction strength in TiN can be as high as 8.5 eV

TiN exhibits strong electronic correlations

High-quality TiN films confirmed by structural and transport measurements

Abstract

Although transition-metal nitrides have been widely applied for several decades, experimental investigations of their high-resolution electronic band structures are rare due to the lack of high-quality single-crystalline samples. Here, we report on the first momentum-resolved electronic band structures of titanium nitride (TiN) films, a remarkable nitride superconductor. The measurements of crystal structures and electrical transport properties confirmed the high quality of these films. More importantly, with a combination of high-resolution angle-resolved photoelectron spectroscopy and the first-principles calculations, the extracted Coulomb interaction strength of TiN films can be as large as 8.5 eV, whereas resonant photoemission spectroscopy yields a value of 6.26 eV. These large values of Coulomb interaction strength indicate that superconducting TiN is a strongly correlated system. Our results uncover the unexpected electronic correlations in transition-metal nitrides, potentially providing a perspective not only to understand their emergent quantum states but also to develop their applications in quantum devices.