Non-linear charge oscillation driven by a single-cycle light-field in an organic superconductor

TL;DR

This study observes a non-linear, ultrafast charge oscillation in an organic superconductor driven by a single-cycle light field, revealing the role of Coulomb repulsion in superconductivity.

Contribution

It reports the first observation of a non-linear charge oscillation in a superconductor induced by intense light fields, highlighting the importance of Coulomb interactions.

Findings

Non-linear charge oscillation with a 6 fs period observed.

Oscillation enhanced near superconducting transition temperature.

Ultrafast dynamics clarify Coulomb repulsion's role in superconductivity.

Abstract

Intense light-field application to solids produces enormous/ultrafast non-linear phenomena such as high-harmonic generations 1, 2 and attosecond charge dynamics 3, 4. They are distinct from conventional photonics. However, main targets have been limited to insulators and semiconductors, although theoretical approaches have been made also for correlated metals and superconductors 5. Here, in a layered organic superconductor, a non-linear charge oscillation driven by a nearly single-cycle strong electric field of >10 megavolts /cm is observed as a stimulated emission. The charge oscillation is different from a linear response and ascribed to a polar charge oscillation with a period of 6 fs. This non-linear polar charge oscillation is enhanced by critical fluctuations near a superconducting transition temperature and a critical end point of first order Mott transitions. Its observation on an ultrafast timescale of 10 fs clarifies that the Coulomb repulsion plays an essential role in superconductivity of organic superconductors.