Visualizing the interplay of dual electronic nematicities in kagome superconductors

TL;DR

This study uses scanning tunneling microscopy to explore how two distinct nematic orders interact in kagome superconductor CsV$_3$Sb$_5$, revealing their temperature and doping dependence and their orbital origins.

Contribution

It uncovers the coexistence and interplay of two nematic orders in CsV$_3$Sb$_5$, linked to different kagome lattice orbitals, and clarifies their relationship with charge density waves.

Findings

One nematic order persists without breaking transition symmetry at high doping and temperature.

The nematic directors of the two orders are oriented differently at intermediate doping.

The two nematic orders eventually align in the pristine compound, influencing quasiparticle coherence.

Abstract

Kagome superconductor AV$_3$Sb$_5$ (A stands for K, Rb, and Cs) hosts a wealth of intertwined electronic orders driven by geometric frustration and electron correlations. Among them, the breaking of rotational and/or time-reversal symmetry, observed within the triple-$Q$ charge density wave (CDW) phase yet exhibiting a more complex temperature dependence, remains a central puzzle. Here, by using scanning tunneling microscopy to study the electronic structures of CsV$_3$Sb$_5$ as a function of temperature and Ti doping, we disentangle the interrelation between two distinct nematic order parameters, one associated with the CDW and the other manifested as $C_2$ distortion of the V-$d_{x^{2}-y^{2}}$ Fermi pockets without breaking transition symmetry. The latter persists to high doping levels and high temperatures where the long-range CDW is fully suppressed. Moreover, its nematic director is oriented in a lattice direction distinct from that of the CDW-induced nematicity at intermediate doping, and eventually aligns with the strong nematic CDW order in the pristine compound where the quasiparticles of vanadium orbitals become coherent below a lower characteristic temperature. These observations, combined with Ginzburg-Landau analysis, reveal a rich interplay between two nematic orders that can be assigned to distinct kagome-lattice orbitals. Our results shed new light on the enigmatic intertwined orders in this family and establish a rare material platform in which dual nematic orders coexist and couple to give rise to unusual correlated phenomena.