中心对称碲掺杂PtBi₂单晶中的体超导性探测
Probing bulk superconductivity in centrosymmetric Te-doped PtBi$_2$ single crystals
AI总结：
本研究合成碲掺杂PtBi₂单晶，证实其为中心对称结构，观测到临界温度约2.4K的体超导性，点接触测量显示临界温度略升至约3K，为拓扑超导研究提供了中心对称体系的实验依据。
AI中文摘要：
外尔半金属γ-PtBi₂被证实是最具前景的新型材料之一，近期被提出作为拓扑i波超导体。观测该物理现象的关键要求是其三角晶系P31m晶体结构不存在反演对称性。已有研究表明，通过电子掺杂（仅用2%的Te部分替代Bi）可轻易将结构恢复为中心对称的P$\bar{3}$m1结构。本研究合成了碲掺杂PtBi$_{2-x}$Te$_x$样品，并对标称成分为PtBi$_{1.96}$Te$_{0.04}$的选定单晶的体超导性进行了全面研究，该样品展现出约100%的最高超导体积分数。单晶XRD测量证实样品为中心对称的P$\bar{3}$m1结构，而磁化率和比热测量观测到临界温度$T_\text{c} \u2248 2.4$K的体超导性。两个不同取向的上临界场测定为：面内磁场$H^{\u2228}_{\text{c2}}(0)\u2248 6.3$kOe，面外磁场$H^{\u22a5}_{\text{c2}}(0)\u2248 4.7$kOe。电阻和点接触测量中也发现了稳定的超导性，其中点接触测量显示临界温度略有提升至$T_\text{c} \u223c 3$K。最后，ARPES测量证实了样品的中心对称结构，呈现单一表面终止且无费米弧。
英文摘要：
The Weyl semimetal $γ$-PtBi$_2$ has been shown to be one of the most promising novel materials, recently proposed as a topological i-wave superconductor. A crucial requirement for observing this physics is the absence of inversion symmetry in its trigonal $P31m$ crystal structure. Centrosymmetry has been reported to be readily restored in the $P\overline{3}m1$ structure upon electron doping, partially substituting Bi with as little as 2% Te. In this work, we synthesized Te-doped PtBi$_{2-x}$Te$_{x}$ samples and thoroughly investigated the bulk superconductivity of selected single crystals with nominal composition PtBi$_{1.96}$Te$_{0.04}$, exhibiting the highest superconducting volume fraction of $\sim100$%. Single crystal XRD measurements confirm the centrosymmetric $P\overline{3}m1$ structure in our samples, whereas bulk superconductivity with a critical temperature of $T_\mathrm{c} \approx 2.4\,$K was observed in magnetization and specific heat measurements. The upper critical fields for two different orientations were determined as $H^{\parallel}_{\mathrm{c2}}(0)\approx 6.3\,$kOe for in-plane and $H^{\perp}_{\mathrm{c2}}(0)\approx 4.7\,$kOe for out-of-plane magnetic fields. Robust superconductivity was also found in resistance and point contact measurements, where the latter showed a slight enhancement of the critical temperature up to $T_\mathrm{c} \sim 3\,$K. Finally, ARPES measurements corroborate the centrosymmetric structure of our samples, showing a single surface termination and the absence of Fermi arcs.
