Controlled vaporization of the superconducting condensate in cuprate superconductors sheds light on the pairing boson

TL;DR

This study uses ultrafast laser pulses to investigate the vaporization dynamics of the superconducting state in cuprates, revealing that phonons, not spins, mediate pairing, challenging previous spin-mediated theories.

Contribution

It provides direct femtosecond-scale evidence that phonons, rather than spins, are responsible for pairing in cuprate superconductors, based on energy relaxation analysis.

Findings

Superconducting vaporization energy exceeds condensation energy.

Energy sharing with boson bath suggests phonon mediation.

Spin-mediated pairing is effectively ruled out.

Abstract

We use ultrashort intense laser pulses to study superconducting state vaporization dynamics in La(2-x)Sr(x)CuO4 (x=0.1 and 0.15) on the femtosecond timescale. We find that the energy density required to vaporize the superconducting state is 2+- 0.8 K/Cu and 2.6 +- 1 K/Cu for x=0.1 and 0.15 respectively. This is significantly greater than the condensation energy density, indicating that the quasiparticles share a large amount of energy with the boson glue bath on this timescale. Considering in detail both spin and lattice energy relaxation pathways which take place on the relevant timescale of picoseconds, we rule out purely spin-mediated pair-breaking in favor of phonon-mediated mechanisms, effectively ruling out spin-mediated pairing in cuprates as a consequence.