Pauli-Limited Multiband Superconductivity in KFe2As2

D. A. Zocco; K. Grube; F. Eilers; T. Wolf; H. v. Löhneysen

doi:10.1103/PhysRevLett.111.057007

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Pauli-Limited Multiband Superconductivity in KFe2As2

D. A. Zocco, K. Grube, F. Eilers, T. Wolf, H. v. Löhneysen

DOI 10.1103/PhysRevLett.111.057007 · Physical Review Letters

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Abstract

The upper critical field Hc2(T) of the multiband superconductor KFe2As2 has been studied via low-temperature thermal expansion and magnetostriction measurements. We present compelling evidence for Pauli-limiting effects dominating Hc2(T) for H∥a, as revealed by a crossover from second- to first-order phase transitions to the superconducting state in the magnetostriction measurements down to 50 mK. Corresponding features were absent for H∥c. To our knowledge, this crossover constitutes the first confirmation of Pauli limiting of the Hc2(T) of a multiband superconductor. The results are supported by modeling Pauli limits for single-band and multiband cases.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
KFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.4	Pressure not reported	onset
Ba1-xKxFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	38	Pressure not reported	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown