论文标题
$^{181} $ ta核四极杆共振研究非中心超导体PBTase $ _2 $
$^{181}$Ta Nuclear quadrupole resonance study of non-centrosymmetric superconductor PbTaSe$_2$
论文作者
论文摘要
我们在零磁场上报告了PBTase $ _2 $的纯$^{181} $ ta-核四极共振（NQR）测量，该测量的优势是直接探测Tase $ _2 $ lays的固有超导阶段和电子状态。我们观察到了$^{181} $ ta-nqr频谱，其内在结构具有$ p6 $ - $ m2 $，这与密度功能理论（DFT）计算非常吻合。核自旋松弛率（$ 1/t_1 $）显示指数下降远低于$ t _ {\ rm_c} $，表明超导状态完全掩盖在Bardeen-Cooper-Schrieffer（BCS）理论的框架中。 $^{181} $ TA-NQR获得的间隙大小小于先前报告中的值，这可能意味着由TA-5 $ D $轨道组成的费米表面，预计平均配对相互作用将比BCS模型中的平均配对相互作用较弱。 $ 1/t_1 $以下的温度依赖性低于$ t _ {\ rm_c} $，可以通过四极杆和磁性松弛机制的叠加来很好地复制，以及在理论上提出了多个FERMI均值固有的差距大小固有的间隙大小的分布。
We report on a pure $^{181}$Ta-nuclear quadrupole resonance (NQR) measurement of PbTaSe$_2$ at zero magnetic field, which has the advantage of directly probing the intrinsic superconducting phase and electronic states of the TaSe$_2$ layer. We observed the $^{181}$Ta-NQR spectrum of the intrinsic structure with space group $P6$-$m2$, which agrees well with density functional theory (DFT) calculations. The nuclear spin relaxation rate ($1/T_1$) shows an exponential decrease well below $T_{\rm_c}$, indicating that the superconducting state is fully gapped in the framework of Bardeen-Cooper-Schrieffer (BCS) theory. The gap size obtained by $^{181}$Ta-NQR was smaller than the value in previous reports, which may imply that the Fermi surfaces composed of Ta-5$d$ orbitals, where the average pairing interactions are expected to be weaker than in BCS model, are primarily probed. The temperature dependence of $1/T_1$ below $T_{\rm_c}$ can be reproduced well by the superposition of quadrupole and magnetic relaxation mechanisms, together with the distribution of superconducting gap size inherent to multiple Fermi surfaces theoretically proposed in PbTaSe$_2$.
