Dawson R D, Rabinovich K S, Putzky D, Christiani G, Logvenov G, Keimer B, Boris A V
Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Phys Rev Lett. 2020 Dec 4;125(23):237001. doi: 10.1103/PhysRevLett.125.237001.
The temperature dependence of the superfluid density ρ_{s}(T) has been measured for a series of ultrathin MBE-grown DyBa_{2}Cu_{3}O_{7-δ} superconducting (SC) films by submillimeter wave interferometry combined with time-domain terahertz spectroscopy and IR ellipsometry. We find that all films 10 u.c. and thicker show the same universal temperature dependence of ρ_{s}(T), which follows the critical behavior characteristic of single crystal YBa_{2}Cu_{3}O_{7-δ} as T approaches T_{c}. In 7 u.c. thick films, ρ_{s}(T) declines steeply upon approaching T_{c}, as expected for the Berezinskii-Kosterlitz-Thouless vortex unbinding transition. Our analysis provides evidence for a sharply defined 4 u.c. non-SC interfacial layer, leaving a quasi-2D SC layer on top. We propose that the SC state in this interfacial layer is suppressed by competing (possibly charge) order.
通过亚毫米波干涉测量法结合时域太赫兹光谱和红外椭偏测量法，对一系列通过分子束外延（MBE）生长的超薄DyBa₂Cu₃O₇₋δ超导（SC）薄膜的超流密度ρₛ(T)的温度依赖性进行了测量。我们发现，所有厚度为10个晶胞及以上的薄膜都表现出相同的ρₛ(T)的通用温度依赖性，当温度接近Tc时，其遵循单晶YBa₂Cu₃O₇₋δ的临界行为特征。在厚度为7个晶胞的薄膜中，随着接近Tc，ρₛ(T)急剧下降，这正如Berezinskii-Kosterlitz-Thouless涡旋解束缚转变所预期的那样。我们的分析为一个明确界定的4个晶胞厚的非超导界面层提供了证据，在其顶部留下了一个准二维超导层。我们提出，该界面层中的超导态被竞争性（可能是电荷）有序所抑制。
