Coupling between electrons and charge density wave fluctuation and its possible role in superconductivity

TL;DR

This study provides evidence of electron coupling with charge density wave fluctuations in 2H-PdxTaSe2, suggesting this interaction may mediate superconductivity and influence the competition between different electronic orders.

Contribution

It demonstrates the coupling between electrons and CDW fluctuations through ARPES measurements and links this coupling to superconducting properties, offering new insights into the CDW-superconductivity relationship.

Findings

Kinks in ARPES spectra indicate electron-CDW fluctuation coupling.

Coupling strength increases as long-range CDW order is suppressed.

Estimated Tc from coupling data matches the superconducting dome.

Abstract

In most of charge density wave (CDW) systems of different material classes, ranging from traditional correlated systems in low-dimension to recent topological systems with Kagome lattice, superconductivity emerges when the system is driven toward the quantum critical point (QCP) of CDW via external parameters of doping and pressure. Despite this rather universal trend, the essential hinge between CDW and superconductivity has not been established yet. Here, the evidence of coupling between electron and CDW fluctuation is reported, based on a temperature- and intercalation-dependent kink in the angle-resolved photoemission spectra of 2H-PdxTaSe2. Kinks are observed only when the system is in the CDW phase, regardless of whether a long- or short-range order is established. Notably, the coupling strength is enhanced upon long-range CDW suppression, albeit the coupling energy scale is reduced. Interestingly, estimation of the superconducting critical temperature by incorporating the observed coupling characteristics into McMillan's equation yields result closely resembling the known values of the superconducting dome. Our results thus highlight a compelling possibility that this new coupling mediates Cooper pairs, which provides new insights on the competing relationship not only for CDW, but also for other competing orders.