Ultrafast Orbital-Selective Photodoping Melts Charge Order in Overdoped Bi-based Cuprates

TL;DR

This study demonstrates that ultrafast laser pulses at specific wavelengths can selectively melt charge order in overdoped cuprates, revealing orbital-specific electronic dynamics and universal recovery times, advancing control over quantum phases.

Contribution

It introduces orbital-selective photodoping using ultrafast laser pulses to control charge order in overdoped cuprates, a novel approach in correlated electron systems.

Findings

400 nm photons effectively melt charge order, 800 nm do not

Charge order recovery time is approximately 3 ps

Higher fluence is needed to melt charge order in overdoped samples

Abstract

High-temperature superconductivity in cuprates remains one of the enduring puzzles of condensed matter physics, with charge order (CO) playing a central yet elusive role, particularly in the overdoped regime. Here, we employ time-resolved X-ray absorption spectroscopy and resonant X-ray scattering at a free-electron laser to probe the transient electronic density of states and ultrafast CO dynamics in overdoped (Bi,Pb)$_{2.12}$Sr$_{1.88}$CuO$_{6+\delta}$. We reveal a striking pump laser wavelength dependence - the 800 nm light fails to suppress CO, whereas the 400 nm light effectively melts it. This behavior originates from the fact that 400 nm photons can promote electrons from the Zhang-Rice singlet band to the upper Hubbard band or apical oxygen states, while 800 nm photons lack the energy to excite electrons across the charge-transfer gap. The CO recovery time ($\sim$3 ps) matches that of the underdoped cuprates, indicating universal electronic instability in the phase diagram. Additionally, melting overdoped CO requires an order-of-magnitude higher fluence highlighting the role of lattice interactions. Our findings demonstrate orbital-selective photodoping and provide a route to ultrafast control of emergent quantum phases in correlated materials.