Campus Units

Physics and Astronomy, Ames Laboratory

Document Type

Article

Publication Version

Published Version

Publication Date

8-1-2016

Journal or Book Title

Physical Review B

Volume

94

Issue

6

First Page

064501

DOI

10.1103/PhysRevB.94.064501

Abstract

Single-crystalline, single-phase CaKFe 4 As 4 has been grown out of a high-temperature, quaternary melt. Temperature-dependent measurements of x-ray diffraction, anisotropic electrical resistivity, elastoresistivity, thermoelectric power, Hall effect, magnetization, and specific heat, combined with field-dependent measurements of electrical resistivity and field and pressure-dependent measurements of magnetization indicate that CaKFe 4 As 4 is an ordered, stoichiometric, Fe-based superconductor with a superconducting critical temperature, T c = 35.0 ± 0.2 K. Other than superconductivity, there is no indication of any other phase transition for 1.8 K ≤ T ≤ 300 K. All of these thermodynamic and transport data reveal striking similarities to those found for optimally or slightly overdoped ( Ba 1 − x K x ) Fe 2 As 2 , suggesting that stoichiometric CaKFe 4 As 4 is intrinsically close to what is referred to as “optimal-doped” on a generalized, Fe-based superconductor, phase diagram. The anisotropic superconducting upper critical field, H c 2 ( T ) , of CaKFe 4 As 4 was determined up to 630 kOe. The anisotropy parameter γ ( T ) = H ⊥ c 2 / H ∥ c 2 , for H applied perpendicular and parallel to the c axis, decreases from ≃ 2.5 at T c to ≃ 1.5 at 25 K, which can be explained by interplay of paramagnetic pair breaking and orbital effects. The slopes of d H ∥ c 2 / d T ≃ − 44 kOe/K and d H ⊥ c 2 / d T ≃ − 109 kOe/K at T c yield an electron mass anisotropy of m ⊥ / m ∥ ≃ 1 / 6 and short Ginzburg-Landau coherence lengths ξ ∥ ( 0 ) ≃ 5.8 Å and ξ ⊥ ( 0 ) ≃ 14.3 Å . The value of H ⊥ c 2 ( 0 ) can be extrapolated to ≃ 920 kOe, well above the BCS paramagnetic limit.

Comments

This article is published as Meier, W. R., T. Kong, U. S. Kaluarachchi, V. Taufour, N. H. Jo, G. Drachuck, A. E. Böhmer et al. "Anisotropic thermodynamic and transport properties of single-crystalline CaKFe 4 As 4." Physical Review B 94, no. 6 (2016): 064501. DOI: 10.1103/PhysRevB.94.064501. Posted with permission.

Copyright Owner

American Physical Society

Language

en

File Format

application/pdf

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