Nodeless superconductivity in the type-II Dirac semimetal PdTe2 : London penetration depth and pairing-symmetry analysis
Nodeless superconductivity in the type-II Dirac semimetal PdTe2 : London penetration depth and pairing-symmetry analysis
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DOI：
10.1103/physrevb.98.024508
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发表时间：
2018-04
影响因子：
3.7
通讯作者：
S. Teknowijoyo;N. Jo;M. Scheurer;M. Tanatar;K. Cho;S. Bud’ko;P. P. Orth-P.;P. Canfield;R. Prozorov-R.
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文献类型：
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作者：
S. Teknowijoyo;N. Jo;M. Scheurer;M. Tanatar;K. Cho;S. Bud’ko;P. P. Orth-P.;P. Canfield;R. Prozorov-R.
通过使用隧道二极管谐振器技术测量伦敦穿透深度来探测II型狄拉克半金属PdTe$_2$中的超导间隙结构。在低温下，两个样品的超流数据都可以用弱耦合指数拟合来描述，在固定的$\Delta（0）/Tc\约为1.76$时，$\lambda（T=0）=230$~nm是唯一的拟合参数，计算的超流密度与具有单能隙尺度的完全能隙超导态相一致.面内和面间电流方向的电阻率测量发现非常低且几乎与温度无关的正常状态各向异性。电阻率的温度依赖性对于金属中的常规声子散射是典型的。我们比较这些实验结果与期望从一个详细的理论对称性分析和减少可能的超导配对状态的PdTe$_2$只有三个无节点的候选人：一个经常的，拓扑平凡的，$s$波配对，和两个不同的奇宇称三重态，都可以是拓扑非平凡的微观相互作用驱动的超导不稳定性。
Superconducting gap structure was probed in type-II Dirac semimetal PdTe$_2$ by measuring the London penetration depth using tunnel diode resonator technique. At low temperatures, the data for two samples are well described by weak coupling exponential fit yielding $\lambda(T=0)=230$~nm as the only fit parameter at a fixed $\Delta(0)/T_c\approx 1.76$, and the calculated superfluid density is consistent with a fully gapped superconducting state characterized by a single gap scale. Electrical resistivity measurements for in-plane and inter-plane current directions find very low and nearly temperature-independent normal- state anisotropy. The temperature dependence of resistivity is typical for conventional phonon scattering in metals. We compare these experimental results with expectations from a detailed theoretical symmetry analysis and reduce the number of possible superconducting pairing states in PdTe$_2$ to only three nodeless candidates: a regular, topologically trivial, $s$-wave pairing, and two distinct odd-parity triplet states that both can be topologically non-trivial depending on the microscopic interactions driving the superconducting instability.