TY - JOUR
T1 - Quantum vortex melting and phase diagram in the layered organic superconductor κ -(BEDT-TTF) 2Cu(NCS)2
AU - Uji, S.
AU - Fujii, Y.
AU - Sugiura, S.
AU - Terashima, T.
AU - Isono, T.
AU - Yamada, J.
N1 - Funding Information:
This work was supported by a Grant-in-Aid for Scientific Research from MEXT (Grant No. 17H01144).
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/1/8
Y1 - 2018/1/8
N2 - Resistance and magnetic torque measurements have been performed to investigate vortex phases for a layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene], which is modeled as stacks of Josephson junctions. At 25 mK, the out-of-plane resistivity increases at 0.6 T, has a step feature up to 4 T, and then increases again, whereas the in-plane resistivity monotonically increases above 4 T. The results show that both pancake vortices (PVs) and Josephson vortices (JVs) are in solid phases for μ0H<0.6 T, but only JVs are in a liquid phase for 0.6<μ0H<4 T. For μ0H>4 T, both PVs and JVs are in liquid phases. These melting transitions are predominantly induced by quantum fluctuations (not by thermal fluctuations). In the magnetic torque curves, the irreversibility transition is clearly observed, roughly corresponding to the melting transition of the PVs but no anomaly is found at the JV melting transition. The detailed vortex phase diagram is determined in a wide temperature region.
AB - Resistance and magnetic torque measurements have been performed to investigate vortex phases for a layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene], which is modeled as stacks of Josephson junctions. At 25 mK, the out-of-plane resistivity increases at 0.6 T, has a step feature up to 4 T, and then increases again, whereas the in-plane resistivity monotonically increases above 4 T. The results show that both pancake vortices (PVs) and Josephson vortices (JVs) are in solid phases for μ0H<0.6 T, but only JVs are in a liquid phase for 0.6<μ0H<4 T. For μ0H>4 T, both PVs and JVs are in liquid phases. These melting transitions are predominantly induced by quantum fluctuations (not by thermal fluctuations). In the magnetic torque curves, the irreversibility transition is clearly observed, roughly corresponding to the melting transition of the PVs but no anomaly is found at the JV melting transition. The detailed vortex phase diagram is determined in a wide temperature region.
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U2 - 10.1103/PhysRevB.97.024505
DO - 10.1103/PhysRevB.97.024505
M3 - Article
AN - SCOPUS:85040608342
VL - 97
JO - Physical Review B
JF - Physical Review B
SN - 2469-9950
IS - 2
M1 - 024505
ER -