Superconductivity in an organic insulator at very high magnetic fields

Abstract

We investigate by electrical transport the field-induced superconducting state (FISC) in the organic conductor $\hat{I}»$-(BETS)${}_2$FeCl${}_4$. Below 4 K, antiferromagnetic-insulator, metallic, and eventually superconducting (FISC) ground states are observed with increasing in-plane magnetic field. The FISC state survives between 18 and 41 T, and can be interpreted in terms of the Jaccarino-Peter effect, where the external magnetic field {\em compensates} the exchange field of aligned Fe${}^{3+}$ ions. We further argue that the Fe${}^{3+}$ moments are essential to stabilize the resulting singlet, two-dimensional superconducting state

9 pages 3 figures