• A
  • A
  • A
  • ABC
  • ABC
  • ABC
  • А
  • А
  • А
  • А
  • А
Regular version of the site

Article

Superconducting properties of sulfur-doped iron selenide

Physical Review B: Condensed Matter and Materials Physics. 2015. Vol. 91. No. 16. P. 165109-1-165109-12.
V. M. Pudalov, Abdel-Hafiez M., Zhang Y., Cao Z., Duan C., Karapetrov G., Vlasenko V., Sadakov A., Knyazev D., Romanova T., Chareev D., Volkova O., Vasiliev A., Chen X.

The recent discovery of high-temperature superconductivity in single-layer iron selenide has generated
significant experimental interest for optimizing the superconducting properties of iron-based superconductors
through the lattice modification. For simulating the similar effect by changing the chemical composition due to S
doping, we investigate the superconducting properties of high-quality single crystals of FeSe1−xSx (x = 0, 0.04,
0.09, and 0.11) using magnetization, resistivity, the London penetration depth, and low temperature specific heat
measurements. We show that the introduction of S to FeSe enhances the superconducting transition temperature
Tc, anisotropy, upper critical field Hc2, and critical current density Jc. The upper critical field Hc2(T ) and its
anisotropy are strongly temperature dependent, indicating a multiband superconductivity in this system. Through
the measurements and analysis of the London penetration depth λab(T ) and specific heat, we show clear evidence
for strong coupling two-gap s-wave superconductivity. The temperature dependence of λab(T ) calculated from
the lower critical field and electronic specific heat can be well described by using a two-band model with
s-wave-like gaps. We find that a d wave and single-gap BCS theory under the weak-coupling approach cannot
describe our experiments. The change of specific heat induced by the magnetic field can be understood only in
terms of multiband superconductivity.