Doping dependence of the critical fluctuation regime in the Fe-based superconductor Ba1−xKxFe2As2

Jianqiang Hou; Philipp Burger; Huen Kit Mak; Frédéric Hardy; Thomas Wolf; Christoph Meingast; Rolf Lortz

doi:10.1103/PhysRevB.92.064502

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Doping dependence of the critical fluctuation regime in the Fe-based superconductor Ba1−xKxFe2As2

Jianqiang Hou, Philipp Burger, Huen Kit Mak, Frédéric Hardy, Thomas Wolf, Christoph Meingast, Rolf Lortz

DOI 10.1103/PhysRevB.92.064502 · Physical Review B

T1

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Abstract

We investigate the importance of superconducting order parameter fluctuations in the 122 family of Fe-based superconductors, using high-resolution specific heat and thermal expansion data of various Ba1−xKxFe2As2 single crystals covering a large range of the phase diagram from the strongly underdoped to the overdoped regime. By applying scaling relations of the 3d−XY and the 3d−lowest-Landau-level(3d−LLL) fluctuation models to data measured in different magnetic fields, we demonstrate that a strong increase of the critical fluctuation regime is responsible for the transition broadening in magnetic fields, which is a direct consequence of a magnetic-field-induced finite-size effect due to a reduction of the effective dimensionality by a decreasing magnetic length scale related to the mean vortex separation and the confinement of quasiparticles in LLL. The fluctuations are stronger in the underdoped and overdoped regimes and appear to be weakest at optimal doping.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Ba1-xKxFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ba1-xKxFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ba0.5K0.5Fe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	34.3	Pressure not reported	onset
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Nb3Sn Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
V3Si Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown