Photo-induced new metastable state with modulated Josephson coupling strengths in Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$

TL;DR

This study demonstrates that intense NIR photoexcitation can induce a new metastable superconducting phase with modulated Josephson coupling in Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$, rather than destroying superconductivity as previously expected.

Contribution

It reveals that intense NIR pulses can create a metastable superconducting state with modulated Josephson coupling, challenging the conventional understanding of photoinduced effects in superconductors.

Findings

Intense NIR pump induces a metastable superconducting phase.

The new phase features modulated Josephson coupling strengths.

Superconductivity is preserved, not destroyed, under intense photoexcitation.

Abstract

Photoexcitations on a superconductor using ultrafast nir-infrared (NIR) pulses, whose energy is much higher than the superconducting energy gap, are expected to suppress/destroy superconductivity by breaking Cooper pairs and excite quasiparticles from occupied state to unoccupied state far above the Fermi level. This appears to be true only for small pumping fluence. Here we show that the intense NIR pumping has different effect. We perform an intense NIR pump, c-axis terahertz probe measurement on an electron-doped cuprate superconductor Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$ with T$_c$=22 K. The measurement indicates that, instead of destroying superconductivity or exciting quasiparticles, the intense NIR pump drives the system from an equilibrium superconducting state with uniform Josephson coupling strength to a new metastable superconducting phase with modulated Josephson coupling strengths below T$_c$.