Tunable van Hove singularity without structural instability in Kagome metal CsTi$_3$Bi$_5$

TL;DR

This study demonstrates that in the Kagome metal CsTi$_3$Bi$_5$, the van Hove singularity can be tuned over a large energy range without inducing structural instability, offering new insights into electronic instabilities in Kagome metals.

Contribution

The paper reports the first experimental and theoretical investigation showing tunable van Hove singularity in CsTi$_3$Bi$_5$ without structural instability, unlike similar compounds.

Findings

Van Hove singularity can be tuned over a large energy range.

No structural instability accompanies the tuning of the van Hove singularity.

Provides a platform to study electronic instability in Kagome metals.

Abstract

In Kagome metal CsV$_3$Sb$_5$, multiple intertwined orders are accompanied by both electronic and structural instabilities. These exotic orders have attracted much recent attention, but their origins remain elusive. The newly discovered CsTi$_3$Bi$_5$ is a Ti-based Kagome metal to parallel CsV$_3$Sb$_5$. Here, we report angle-resolved photoemission experiments and first-principles calculations on pristine and Cs-doped CsTi$_3$Bi$_5$ samples. Our results reveal that the van Hove singularity (vHS) in CsTi$_3$Bi$_5$ can be tuned in a large energy range without structural instability, different from that in CsV$_3$Sb$_5$. As such, CsTi$_3$Bi$_5$ provides a complementary platform to disentangle and investigate the electronic instability with a tunable vHS in Kagome metals.