Multiband superconductivity and large anisotropy in FeS crystals

Abstract

By using a hydrothermal method, we have successfully grown crystals of the newly discovered superconductor FeS, which has an isostructure of the iron based superconductor FeSe. The superconductivity appears at about 4.5K, as revealed by both resistive and magnetization measurements. It is found that the upper critical field is relatively low, with however an rather large anisotropy Γ = [(dH ab c2 /dT )/(dH c c2 /dT )]T c ≈ 5.8. A huge magnetoresistivity (290% at 9T and 10K, H c-axis) together with a non-linear behavior of Hall resistivity vs. external field are observed. A two-band model is applied to fit the magnetoresistance and non-linear transverse resistivity, yielding the basic parameters of the electron and hole bands.

Upper critical field and quantum oscillations in tetragonal superconducting FeS

“…The anisotropy ratio at T c is Γ(T c ) = 6.9, which is consistent with [8]. We have observed quantum oscillations in both the magnetoresistance and magnetic torque.…”

“…[8]. For fourcontact in-plane resistance measurements, electrical contacts were first attached to four samples with silver paste.…”

“…A nodal or highly anisotropic superconducting gap has been suggested by studies on the specific heat [6] and with scanning tunneling microscopy [9], while a µSR study has suggested that a full-gap state coexists with low-moment disordered magnetism [7]. Large anisotropy of the upper critical field B c2 has been reported [4,8].…”

Observation of two superconducting domes under pressure in tetragonal FeS

“…62 XRD was carried out at room temperature using Bruker D8 Advance diffractometer (Cu K α radiation, λ = 1.5408 Å). Single crystal XRD of FeS was carried out on a Bruker SMART Apex (II) diffractometer (Mo K α radiation, λ = 0.71073 Å).…”

Critical current density and vortex pinning in tetragonalFeS1−xSex(x=0,0.06)

“…6 The superconducting state is multiband with nodal gap and large upper critical field anisotropy. [8][9][10][11] Local probe µSR measurements indicate two s-wave gaps but also a disordered impurity magnetism with small moment that microscopically coexists with bulk superconductivity below superconducting transition temperature.…”