TY - JOUR
T1 - Nodal superconducting gap in LiFeP revealed by NMR
T2 - Contrast with LiFeAs
AU - Fang, A. F.
AU - Zhou, R.
AU - Tukada, H.
AU - Yang, J.
AU - Deng, Z.
AU - Wang, X. C.
AU - Jin, C. Q.
AU - Zheng, Guo Qing
N1 - Publisher Copyright:
© 2021 Chinese Physical Society and IOP Publishing Ltd.
PY - 2021/4
Y1 - 2021/4
N2 - Identifying the uniqueness of FeP-based superconductors may shed new lights on the mechanism of superconductivity in iron-pnictides. Here, we report nuclear magnetic resonance (NMR) studies on LiFeP and LiFeAs which have the same crystal structure but different pnictogen atoms. The NMR spectrum is sensitive to inhomogeneous magnetic fields in the vortex state and can provide the information on the superconducting pairing symmetry through the temperature dependence of London penetration depth λ L. We find that λ L saturates below T ∼ 0.2 T c in LiFeAs, where T c is the superconducting transition temperature, indicating nodeless superconducting gaps. Furthermore, by using a two-gaps model, we simulate the temperature dependence of λ L and obtain the superconducting gaps of LiFeAs, as Δ 1 = 1.2 k B T c and Δ2 = 2.8 k B T c, in agreement with previous result from spin-lattice relaxation. For LiFeP, in contrast, λ L does not show any saturation down to T ∼ 0.03 T c, indicating nodes in the superconducting gap function. Finally, we demonstrate that strong spin fluctuations with diffusive characteristics exist in LiFeP, as in some cuprate high temperature superconductors.
AB - Identifying the uniqueness of FeP-based superconductors may shed new lights on the mechanism of superconductivity in iron-pnictides. Here, we report nuclear magnetic resonance (NMR) studies on LiFeP and LiFeAs which have the same crystal structure but different pnictogen atoms. The NMR spectrum is sensitive to inhomogeneous magnetic fields in the vortex state and can provide the information on the superconducting pairing symmetry through the temperature dependence of London penetration depth λ L. We find that λ L saturates below T ∼ 0.2 T c in LiFeAs, where T c is the superconducting transition temperature, indicating nodeless superconducting gaps. Furthermore, by using a two-gaps model, we simulate the temperature dependence of λ L and obtain the superconducting gaps of LiFeAs, as Δ 1 = 1.2 k B T c and Δ2 = 2.8 k B T c, in agreement with previous result from spin-lattice relaxation. For LiFeP, in contrast, λ L does not show any saturation down to T ∼ 0.03 T c, indicating nodes in the superconducting gap function. Finally, we demonstrate that strong spin fluctuations with diffusive characteristics exist in LiFeP, as in some cuprate high temperature superconductors.
KW - iron-based superconductor
KW - nuclear magnetic resonance
KW - spin fluctuations
KW - superconducting pairing symmetry
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U2 - 10.1088/1674-1056/abec37
DO - 10.1088/1674-1056/abec37
M3 - Article
AN - SCOPUS:85105726067
VL - 30
JO - Chinese Physics B
JF - Chinese Physics B
SN - 1674-1056
IS - 4
M1 - 047403
ER -