Identification of a Critical Doping for Charge Order Phenomena in Bi-2212 Cuprates via RIXS

TL;DR

This study uses RIXS to explore how charge order phenomena evolve with doping in Bi-2212 cuprates, revealing a critical doping point near optimal doping where charge order fluctuations peak and may influence superconductivity.

Contribution

It identifies a critical doping level in Bi-2212 cuprates where charge order fluctuations are maximized, providing new insights into the interplay between charge order and superconductivity.

Findings

Charge order wavevector decreases with doping and saturates at 0.25 r.l.u.

Charge order excitations are strongest near the critical doping pc.

Critical doping pc is close to optimal doping where Tc is maximal.

Abstract

Identifying quantum critical points (QCPs) and their associated fluctuations may hold the key to unraveling the unusual electronic phenomena observed in cuprate superconductors. Recently, signatures of quantum fluctuations associated with charge order (CO) have been inferred from the anomalous enhancement of CO excitations that accompany the reduction of the CO order parameter in the superconducting state. To gain more insight about the interplay between CO and superconductivity, here we investigate the doping dependence of this phenomenon throughout the Bi-2212 cuprate phase diagram using resonant inelastic x-ray scattering (RIXS) at the Cu L3- edge. As doping increases, the CO wavevector decreases, saturating at a commensurate value of 0.25 r.l.u. beyond a characteristic doping pc, where the correlation length becomes shorter than the apparent periodicity (4a0). Such behavior is indicative of the fluctuating nature of the CO; and the proliferation of CO excitations in the superconducting state also appears strongest at pc, consistent with expected behavior at a CO QCP. Intriguingly, pc appears to be near optimal doping, where the superconducting transition temperature Tc is maximal.