标题： 钽硫化物中超导性和电荷密度波的共存：实验与理论 显示英文标题

标题： Coexistence of Superconductivity and Charge Density Wave in Tantalum Disulfide: Experiment and Theory

摘要： 在常压下，二硫化钽（2H-TaS$_2$）中电荷密度波（CDW）和超导性的共存，在施加高达30GPa的静水压力下被增强，从而诱导出典型的穹顶形超导相。 常压下的CDW基态开始于TCDW = 76 K，具有临界小的费米面，发现在Pc = 8.7GPa时被完全抑制。 在Pc附近，我们观察到一个超导穹顶，其最大超导转变温度Tc = 9.1 K。电子结构的第一性原理计算预测，在常压条件下，未畸变的结构在接近实验CDW波矢的有限动量处表现出声子不稳定性。 在压缩过程中，发现这种不稳定性消失，表明CDW序被抑制。 计算揭示了一个电子拓扑转变（ETT），该转变发生在声子不稳定性被抑制之前，这表明ETT本身并不直接导致系统的结构变化。 通过两种独立的方法获得了第一涡旋穿透场的温度依赖性，并推导出了相应的下临界场H$_{c1}$。 虽然d波和单能隙BCS预测无法描述我们的H$_{c1}$实验，但H$_{c1}$的温度依赖性可以通过单能隙各向异性s波序参量很好地描述。 显示英文摘要

摘要： The coexistence of charge density wave (CDW) and superconductivity in tantalum disulfide (2H-TaS$_2$) at ambient pressure, is boosted by applying hydrostatic pressures up to 30GPa, thereby inducing a typical dome-shaped superconducting phase. The ambient pressure CDW ground state which begins at TCDW = 76 K, with critically small Fermi surfaces, was found to be fully suppressed at Pc = 8.7GPa. Around Pc, we observe a superconducting dome with a maximum superconducting transition temperature Tc = 9.1 K. First-principles calculations of the electronic structure predict that, under ambient conditions, the undistorted structure is characterized by a phonon instability at finite momentum close to the experimental CDW wave vector. Upon compression, this instability is found to disappear, indicating the suppression of CDW order. The calculations reveal an electronic topological transition (ETT), which occurs before the suppression of the phonon instability, suggesting that the ETT alone is not directly causing the structural change in the system. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods and the corresponding lower critical field H$_{c1}$ was deduced. While a d wave and single-gap BCS prediction cannot describe our H$_{c1}$ experiments, the temperature dependence of the H$_{c1}$ can be well described by a single-gap anisotropic s-wave order parameter.