Transient Floquet engineering of superconductivity

TL;DR

This paper demonstrates that intense laser fields can transiently enhance superconducting correlations in a driven electronic system, leveraging non-thermal states to achieve this before heating dominates.

Contribution

It introduces a realistic pathway for laser control of electronic orders by transiently boosting superconducting fluctuations using Floquet engineering.

Findings

Significant enhancement of Cooper-pair correlations before high electronic temperature sets in.

Non-thermal driven states maintain lower effective temperature at the Fermi surface.

Short-range fluctuations show detectable signatures in electronic spectra.

Abstract

Intense time-periodic laser fields can transform the electronic structure of a solid into strongly modified Floquet-Bloch bands. While this suggests multiple pathways to induce electronic orders such as superconductivity or charge density waves, the possibility of preparing low-energy phases of Floquet Hamiltonians remains unclear because of the energy absorption at typical experimentally accessible driving frequencies. Here we investigate a realistic pathway towards laser control of electronic orders, which is the transient enhancement of fluctuating orders. Using a conserving Keldysh Green's function formalism, we simulate the build-up of short range Cooper-pair correlations out of a normal metal in the driven attractive Hubbard model. Even for frequencies only slightly above or within the bandwidth, a substantial enhancement of correlations can be achieved before the system reaches a high electronic temperature. This behavior relies on the non-thermal nature of the driven state. The effective temperature of the electrons at the Fermi surface, which more closely determines the superconducting correlations, remains lower than an estimate from the global energy density. Even though short ranged, the fluctuations can have marked signatures in the electronic spectra.