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Thermodynamic evidence for the formation of a Fulde-Ferrell-Larkin-Ovchinnikov phase in the organic superconductor λ−(BETS)2GaCl4

Authors :
Takuya Kobayashi
Yasuhiro Nakazawa
K. Kindo
Atsushi Kawamoto
Shusaku Imajo
Source :
Physical Review B. 103
Publication Year :
2021
Publisher :
American Physical Society (APS), 2021.

Abstract

In this work, the thermodynamic properties of the organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ 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 ${H}_{\mathrm{FFLO}}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}10$ 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 $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$. The thermodynamic anomaly at ${H}_{\mathrm{FFLO}}$ is smeared out. and the low-temperature upper critical field ${H}_{\mathrm{c}2}$ changes significantly if fields are not parallel to the conducting plane, even for a deviation of $\ensuremath{\sim}0.{5}^{\ensuremath{\circ}}$. 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 $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ from a thermodynamic point of view.

Details

ISSN :
24699969 and 24699950
Volume :
103
Database :
OpenAIRE
Journal :
Physical Review B
Accession number :
edsair.doi...........27bb834daaa30e2345ef458a07a88f92
Full Text :
https://doi.org/10.1103/physrevb.103.l220501