Cascade of correlated electron states in a kagome superconductor CsV3Sb5

TL;DR

This study uncovers a sequence of symmetry-breaking electronic states in the kagome superconductor CsV3Sb5, revealing complex co-existing phases and their evolution with temperature, which may shed light on unconventional superconductivity.

Contribution

First spectroscopic imaging study showing a cascade of symmetry-broken states in CsV3Sb5 across a range of temperatures, highlighting electronic complexity in kagome superconductors.

Findings

Detection of tri-directional charge order above Tc

Observation of symmetry breaking and spectral gap opening near Tc

Identification of orbital-selective band renormalization

Abstract

The kagome lattice of transition metal atoms provides an exciting platform to study electronic correlations in the presence of geometric frustration and nontrivial band topology, which continues to bear surprises. In this work, using spectroscopic imaging scanning tunneling microscopy, we discover a cascade of different symmetry-broken electronic states as a function of temperature in a new kagome superconductor, CsV3Sb5. At a temperature far above the superconducting transition Tc ~ 2.5 K, we reveal a tri-directional charge order with a 2a0 period that breaks the translation symmetry of the lattice. As the system is cooled down towards Tc, we observe a prominent V-shape spectral gap opening at the Fermi level and an additional breaking of the six-fold rotation symmetry, which persists through the superconducting transition. This rotation symmetry breaking is observed as the emergence of an additional 4a0 unidirectional charge order and strongly anisotropic scattering in differential conductance maps. The latter can be directly attributed to the orbital-selective renormalization of the V kagome bands. Our experiments reveal a complex landscape of electronic states that can co-exist on a kagome lattice, and provide intriguing parallels to high-Tc superconductors and twisted bilayer graphene.