A phase diagram for light-induced superconductivity in $\kappa$-(ET)$_2$-X

TL;DR

This study maps the phase diagram of light-induced superconductivity in $$-(BEDT-TTF)$_2$X compounds, showing it occurs only near the Mott insulator phase, suggesting proximity to insulating states is crucial.

Contribution

It provides the first comprehensive phase diagram for light-induced superconductivity across different $$-(BEDT-TTF)$_2$X materials, highlighting the importance of proximity to the Mott insulating phase.

Findings

Photoinduced superconductivity observed only in $$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br

Proximity to Mott insulating phase is necessary for the effect

Preexisting superconducting fluctuations may facilitate light-induced superconductivity

Abstract

Resonant optical excitation of certain molecular vibrations in $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br has been shown to induce transient superconducting-like optical properties at temperatures far above equilibrium $T_c$. Here, we report experiments across the bandwidth-tuned phase diagram of this class of materials, and study the Mott insulator $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Cl and the metallic compound $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$. We find non-equilibrium photoinduced superconductivity only in $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br, indicating that the proximity to the Mott insulating phase and possibly the presence of preexisting superconducting fluctuations are pre-requisites for this effect.