Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates

TL;DR

This study uncovers the role of high-energy electronic excitations in cuprates that are linked to the onset of high-temperature superconductivity, using a novel optical technique to observe their dynamics.

Contribution

It introduces a new optical supercontinuum-probe method to study high-energy excitations and their connection to superconductivity in cuprates.

Findings

High-energy CuO2 excitations are linked to superconductivity onset.

The optical technique reveals dynamics of dielectric function over extended energy range.

Unconventional mechanisms are involved in high-temperature superconductivity.

Abstract

In strongly-correlated systems the electronic properties at the Fermi energy (EF) are intertwined with those at high energy scales. One of the pivotal challenges in the field of high-temperature superconductivity (HTSC) is to understand whether and how the high energy scale physics associated with Mott-like excitations (|E-E$_{F}$|>1 eV) is involved in the condensate formation. Here we show the interplay between the many-body high-energy CuO2 excitations at 1.5 and 2 eV and the onset of HTSC. This is revealed by a novel optical pump supercontinuum-probe technique, which provides access to the dynamics of the dielectric function in Bi$_2$Sr$_2$Ca$_{0.92}$Y$_{0.08}$Cu$_2$O$_{8+{\delta}}$ over an extended energy range, after the photoinduced suppression of the superconducting pairing. These results unveil an unconventional mechanism at the base of HTSC both below and above the optimal hole concentration required to attain the maximum critical temperature (T$_c$).