Ultrafast Carrier Dynamics in an Organic Superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br by Spectrally Resolved Pump-Probe Spectroscopy

Abstract

In this work, spectrally-resolved optical pump probe measurements were carried out on strongly correlated organic superconductor κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br. We find two different types of carrier relaxation dynamics, one of which appears at 1.82 eV and 1.94 eV, and another at 2.17 eV. The former is characterized by short decay time ∼ 1 -2 ps and appears below ∼ 60 K. From the comparison with the previous studies, the dynamics arises from the photoinduced pseudogap (PG) formation of the partially-appeared Mott phase. The latter has long relaxation time ∼ 9 ps at 5 K and developed as temperature decreases below 30 K. The slow dynamics is consistent with appearance of superconducting (SC) gap. Such separate observation of PG and SC dynamics enables us to proceed further investigation of a relationship between them.

Superconductivity in Quantum Complex Matter: the Superstripes Landscape

“…Organic superconductors form another class of superconductors showing the realization of a superconducting dome of multigap superconductivity in superlattices of quantum wires described by Mazziotti [86]. At Superstripes 2019 Tsuchiya et al [87] and Nakagawa et al, [88] have reported the most recent results on the investigation of carrier dynamics and phase separation by spectrally resolved pump-probe spectroscopy and polarized time-resolved spectroscopy of electronic phase separation. Arrested nanoscale phase separation was predicted for multiband correlated metals near a topological Lifshitz transition [89] which is reached by tuning strain and charge [90] with a complex landscape of polaronic short range charge density waves [91].…”

Enhancement of polarization anisotropy in ultrafast carrier dynamics by intramolecular excitation in the organic conductor κ-(BEDT- TTF)2Cu(NCS)2

“…An optical pump broadband-probe spectroscopy is a powerful technique to reveal a wide range of photo-induced changes in the electronic spectrum. So far, this technique has uncovered the high-energy spectral change due to the SC transition and pseudogap (PG) formation in cuprates [17,18] and κ-Br [19], as well as carrier relaxation associated with the spin-density-wave state in pnictides [20]. Therefore, by applying this technique to κ-NCS, we can obtain critical insights into the origin of the AP dynamics.…”