Volume 94, Number 5, June 2011
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||27 May 2011|
Small anisotropy of the lower critical field and the s±-wave two-gap feature in single-crystal LiFeAs
Department of Physics, Sungkyunkwan University - Suwon 440-746, Republic of Korea
2 Initiative Center for Superconductivity, Department of Physics, Sogang University Seoul 121-741, Republic of Korea
3 Department of Chemistry, Pohang University of Science and Technology - Pohang 790-784, Republic of Korea
4 Department of Physics, Chonnam National University - Kwangju 500-757, Republic of Korea
Accepted: 27 April 2011
The in- and out-of-plane lower critical fields and magnetic penetration depths of LiFeAs were examined. The anisotropy ratio ΓHc1(0) was smaller than the expected theoretical value, and increased slightly with increasing temperature from 0.6Tc to Tc. The small degree of anisotropy was numerically confirmed by considering the electron correlation effect. The temperature dependence of the penetration depths followed a power law (∼Tn) below 0.3Tc, with n>3.5 for both λab and λc. Based on theoretical studies of iron-based superconductors, these results suggest that the superconductivity of LiFeAs can be represented by an extended s±-wave due to the weak impurity scattering effect. And the magnitudes of the two gaps were also evaluated by fitting the superfluid density for both the in- and out-of-plane directions to the two-gap model. The estimated values for the two gaps are consistent with the results from angle-resolved photoemission spectroscopy and specific-heat experiments.
PACS: 74.70.Xa – Pnictides and chalcogenides / 74.20.Rp – Pairing symmetries (other than s-wave) / 74.25.Op – Mixed states, critical fields, and surface sheaths
© EPLA, 2011
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