Dispersive charge density wave excitations and temperature dependent commensuration in Bi2Sr2CaCu2O8+{\delta}

TL;DR

This study uses resonant inelastic x-ray scattering to explore charge density wave excitations in underdoped Bi2Sr2CaCu2O8+{eta}, revealing dispersive excitations, phonon anomalies, and temperature-dependent changes in CDW periodicity related to the pseudogap.

Contribution

It provides new insights into the dispersive nature of CDW excitations and their temperature-dependent commensuration in high-Tc cuprates, advancing understanding of their relation to the pseudogap.

Findings

Dispersive CDW excitations observed at low temperature.

CDW persists near pseudogap temperature but weakens and shifts wavevector.

CDW becomes nearly commensurate with four lattice constants at T*.

Abstract

Experimental evidence on high-Tc cuprates reveals ubiquitous charge density wave (CDW) modulations, which coexist with superconductivity. Although the CDW had been predicted by theory, important questions remain about the extent to which the CDW influences lattice and charge degrees of freedom and its characteristics as functions of doping and temperature. These questions are intimately connected to the origin of the CDW and its relation to the mysterious cuprate pseudogap. Here, we use ultrahigh resolution resonant inelastic x-ray scattering (RIXS) to reveal new CDW character in underdoped Bi2Sr2CaCu2O8+{\delta} (Bi2212). At low temperature, we observe dispersive excitations from an incommensurate CDW that induces anomalously enhanced phonon intensity, unseen using other techniques. Near the pseudogap temperature T*, the CDW persists, but the associated excitations significantly weaken and the CDW wavevector shifts, becoming nearly commensurate with a periodicity of four lattice constants. The dispersive CDW excitations, phonon anomaly, and temperature dependent commensuration provide a comprehensive momentum space picture of complex CDW behavior and point to a closer relationship with the pseudogap state.