Thermodynamic evidence for the formation of a Fulde-Ferrell-Larkin-Ovchinnikov phase in the organic superconductor $\lambda$-(BETS)${}_2$GaCl${}_4$

Abstract

In this work, the thermodynamic properties of the organic superconductor $\lambda$-(BETS)${}_2$GaCl${}_4$ are investigated to study a high-field superconducting state known as the putative Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We observed a small thermodynamic anomaly in the field $H_{\mathrm{FFLO}}$ $\sim$ 10~T, which corresponds to the Pauli limiting field $H_{\mathrm{P}}$. This anomaly probably originates from a transition from a uniform superconducting state to the FFLO state. $H_{\mathrm{FFLO}}$ does not show a strong field-angular dependence due to a quasi-isotropic paramagnetic effect in $\lambda$-(BETS)${}_2$GaCl${}_4$. The thermodynamic anomaly at $H_{\mathrm{FFLO}}$ is smeared out and low-temperature upper critical field $H_{c2}$ changes significantly if fields are not parallel to the conducting plane even for a deviation of $\sim$0.5${}^{\circ }$. This behavior indicates that the high-field state is very unstable, as it is influenced by the strongly anisotropic orbital effect. Our results are consistent with the theoretical predictions on the FFLO state, and show that the high-field superconductivity is probably an FFLO state in $\lambda$-(BETS)${}_2$GaCl${}_4$ from a thermodynamic point of view.

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Cited by in corpus (6)

• Fulde-Ferrell-Larkin-Ovchinnikov state induced by antiferromagnetic order in $\kappa$-type organic conductors
• Modulation vector of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn5 revealed by high-resolution magnetostriction measurements
• Dimensional crossover on multileg attractive-$U$ Hubbard ladders
• Fulde-Ferrell-Larkin-Ovchinnikov state in a superconducting thin film attached to a ferromagnetic cluster
• Kink in Stoner Factor as a Signature of Changing Magnetic Fluctuations in the Organic Conductor $\lambda$-(BETS)${}_2$GaCl${}_4$
• Microscopic evidence for Fulde-Ferrel-Larkin-Ovchinnikov state and multiband effects in KFe${}_2$As${}_2$