| 1. |
- Smylie, M. P., et al.
(författare)
-
Anisotropic superconductivity and magnetism in single-crystal RbEuFe4As4
- 2018
-
Ingår i: Physical Review B. - College Park : American Physical Society. - 2469-9950 .- 2469-9969. ; 98:10
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the anisotropic superconducting and magnetic properties of single-crystal RbEuFe4As4 using magnetotransport and magnetization measurements. We determine a magnetic ordering temperature of the Eu moments of Tm=15K and a superconducting transition temperature of Tc=36.8K. The superconducting phase diagram is characterized by high upper critical field slopes of -70 and -42 kG/K for in-plane and out-of-plane fields, respectively, and a surprisingly low superconducting anisotropy of Γ=1.7. Ginzburg-Landau parameters of κc∌67 and κab∌108 indicate extreme type-II behavior. These superconducting properties are in line with those commonly seen in optimally doped Fe-based superconductors. In contrast, Eu magnetism is quasi-two dimensional (2D), as evidenced by highly anisotropic in-plane and out-of-plane exchange constants of 0.6 K and <0.04 K. A consequence of the quasi-2D nature of the Eu magnetism are strong magnetic fluctuation effects, a large suppression of the magnetic ordering temperature as compared to the Curie-Weiss temperature, and a kinklike anomaly in the specific heat devoid of any singularity. Magnetization curves reveal a clear magnetic easy-plane anisotropy with in-plane and out-of-plane saturation fields of 2 and 4 kG. © 2018 American Physical Society.
|
|
| 2. |
- Chapai, R., et al.
(författare)
-
Superconducting properties of the spin Hall candidate Ta3Sb with eightfold degeneracy
- 2022
-
Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 105:18
-
Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis and characterization of phase pure Ta3Sb, a material predicted to be topological with eightfold degenerate fermionic states [Bradlyn et al., Science 353, aaf5037 (2016)] and to exhibit a large spin Hall effect [Derunova et al., Sci. Adv. 5, eaav8575 (2019)]. We observe superconductivity in Ta3Sb with Tc∼0.67 K in both electrical resistivity ρ(T) and specific heat c(T) measurements. Field-dependent measurements yield the superconducting phase diagram with an upper critical field of Hc2(0)∼ 0.95 T, corresponding to a superconducting coherence length of ξ≈18.6nm. The gap ratio deduced from specific heat anomaly 2Δ0/kBTc is 3.46, a value close to the Bardeen-Cooper-Schrieffer value of 3.53. From a detailed analysis of both the transport and thermodynamic data within the Ginsburg-Landau (GL) framework, a GL parameter of κ≈90 is obtained, identifying Ta3Sb as an extreme type-II superconductor. The observation of superconductivity in an eightfold degenerate fermionic compound with topological surface states and predicted large spin Hall conductance positions Ta3Sb as an appealing platform to further explore exotic quantum states in multifold degenerate systems.
|
|
