Photo-enhanced antinodal conductivity in the pseudogap state of high Tc cuprates

TL;DR

This study uses ultrashort light pulses to reveal that photo-excitation enhances antinodal conductivity in the pseudogap state of high-Tc cuprates, indicating a transition from localized to delocalized electronic states.

Contribution

It demonstrates a novel photo-induced transition in the pseudogap phase, linking ultrafast spectroscopy with the Hubbard model to explain antinodal quasiparticle dynamics.

Findings

Decrease in charge carrier scattering rate in pseudogap region

Photo-excitation induces antinodal excitations to become delocalized

Supports k-space differentiation between nodal and antinodal states

Abstract

A major challenge in understanding the cuprate superconductors is to clarify the nature of the fundamental electronic correlations that lead to the pseudogap phenomenon. Here we use ultrashort light pulses to prepare a non-thermal distribution of excitations and capture novel properties that are hidden at equilibrium. Using a broadband (0.5-2 eV) probe we are able to track the dynamics of the dielectric function, unveiling an anomalous decrease of the scattering rate of the charge carriers in a pseudogap-like region of the temperature ($T$) and hole-doping ($p$) phase diagram. In this region, delimited by a well-defined $T^*_{neq}(p)$ line, the photo-excitation process triggers the evolution of antinodal excitations from gapped (localized) to delocalized quasi-particles characterized by a longer lifetime. The novel concept of photo-enhanced antinodal conductivity is naturally explained within the single-band Hubbard model, in which the short-range Coulomb repulsion leads to a k-space differentiation between "nodal" quasiparticles and antinodal excitations.