Evidence for unconventional superconductivity in half-Heusler YPdBi and TbPdBi compounds revealed by London penetration depth measurements
Evidence for unconventional superconductivity in half-Heusler YPdBi and TbPdBi compounds revealed by London penetration depth measurements
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DOI：
10.1103/physrevb.98.241111
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发表时间：
2018-11
影响因子：
3.7
通讯作者：
S. Radmanesh;C. Martin;Yanglin Zhu;X. Yin;H. Xiao;Z. Mao;L. Spinu
中科院分区：
文献类型：
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作者：
S. Radmanesh;C. Martin;Yanglin Zhu;X. Yin;H. Xiao;Z. Mao;L. Spinu
半heusler化合物YPdBi和TbPdBi虽然具有相似的能带结构，但具有不同的磁性能。YPdBi为抗磁体，TbPdBi在5.5 K以下呈反铁磁序。两者都是超导体，YPdBi的T为${_c}\approx$ 1k， TbPdBi的T为${_c}\approx$ 1.75 K。这两种化合物在性质上的这种差异引出了一个关于能带结构或磁相关性对超导性的影响的问题。利用隧道二极管振荡器（TDO）和商用稀释冰箱的组合，我们测量了温度依赖于YPdBi和TbPdBi单晶的磁穿透深度$\Delta\lambda(T)$，温度低至0.1K。我们发现这两种化合物的穿透深度在低温下不表现出指数温度依赖和饱和，正如传统BCS超导体所期望的那样。相反，在这两种化合物中，穿透深度可以用幂律$\Delta\lambda(T) = A\times T^{n}$来描述。TbPdBi的A系数约小50 $\%$，但指数非常相似，YPdBi为$n = 2.76\pm 0.04$， TbPdBi为$n = 2.6\pm 0.3$。我们的研究结果表明YPdBi和TbPdBi都具有非常规的超导性。
The half-Heusler compounds YPdBi and TbPdBi, while having similar band structure, exhibit different magnetic properties. YPdBi is a diamagnet, while TbPdBi shows antiferromagnetic order below 5.5 K. Both are superconductors with T${_c}\approx$1 K for YPdBi and T${_c}\approx$1.75 K for TbPdBi. Such a contrast in properties between these two compounds opens a question about the effects of band structure or magnetic correlations on superconductivity. Using the combination of a tunnel diode oscillator (TDO) and a commercial dilution refrigerator, we measured temperature dependent magnetic penetration depth $\Delta\lambda(T)$ in single crystals of YPdBi and TbPdBi, down to temperatures as low as 0.1K. We found that penetration depths of both compounds do not show exponential temperature dependence and saturation at low temperatures, as expected for conventional BCS superconductors. Instead, in both compounds, the penetration depth can be described by a power law $\Delta\lambda(T) = A\times T^{n}$. The coefficient A was found to be about 50$\%$ smaller in TbPdBi, but the exponents are very similar, $n = 2.76\pm 0.04$ in YPdBi and $n = 2.6\pm 0.3$ in TbPdBi, respectively. Our results suggest unconventional superconductivity in both YPdBi and TbPdBi.