Antiferromagnetic fluctuations in the quasi-two-dimensional organic superconductor detected by Raman spectroscopy

TL;DR

This study uses Raman spectroscopy to detect antiferromagnetic fluctuations in a quasi-two-dimensional organic superconductor and related antiferromagnet, revealing similar magnetic correlations in both compounds.

Contribution

It demonstrates the presence of antiferromagnetic correlations in the superconductor using Raman scattering, a technique not previously applied to these organic conductors.

Findings

Broad Raman band at 500 cm-1 develops below 200 K

Two-magnon excitation identified in both compounds

Similar temperature dependence of magnetic spectral weight

Abstract

Using Raman scattering, the quasi-two dimensional organic superconductor k-(BEDT-TTF)2Cu[N(CN)2]Br (T_c=11.8 K) and the related antiferromagnet k-(BEDT-TTF)2Cu[N(CN)2]Cl are studied. Raman scattering provides unique spectroscopic information about magnetic degrees of freedom that has been otherwise unavailable on such organic conductors. Below T=200 K a broad band at about 500 cm-1 develops in both compounds. We identify this band with two-magnon excitation. The position and the temperature dependence of the spectral weight are similar in the antiferromagnet and in the metallic Fermi-liquid. We conclude that antiferromagnetic correlations are similarly present in the magnetic insulator and the Fermi-liquid state of the superconductor.