CsV$_3$Sb$_5$中准粒子干涉揭示的超导动量结构与亚晶格效应
Momentum Structure of Superconductivity and Sublattice Effects from Quasiparticle Interference in CsV$_3$Sb$_5$
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中文总结 AI 辅助
本研究通过亚开尔文扫描隧道显微镜结合准粒子干涉分析，明确了CsV$_3$Sb$_5$中钒$M_z^+$轨道费米面的各向同性超导能隙，限定了能隙各向异性的来源，且未发现配对密度波调制，为笼目超导电性的低能电子结构提供了关键实验依据。
中文摘要 AI 辅助
笼目布洛赫波函数的亚晶格结构编码的量子干涉被广泛认为是关联态（包括手性电荷序、非常规超导电性及可能的配对密度波（PDW）态）的产生途径。我们采用亚开尔文扫描隧道显微镜，对笼目材料CsV$_3$Sb$_5$在超导能隙范围内进行了高能量分辨率、密集能量采样的光谱测绘。结合从头算与对称性计算的准粒子干涉（QPI）分析显示，源于钒$M_z$偶（$M_z^+$）$d$轨道的费米面存在各向同性超导能隙，这对可能的能隙对称性形成了约束，仅允许剩余的钒$M_z$奇（$M_z^-$）和锑$p_z$带存在能隙各向异性。同时，电荷密度波（CDW）峰选定的微分电导谱（d$I$/d$V$）与空间平均态密度密切匹配，未出现仅局限于能隙内的显著增强，在我们的探测灵敏度范围内不支持额外的PDW调制。最后，特定QPI散射矢量的选择性缺失表明光谱对费米面上的亚晶格特征具有敏感性。综上，这些结果为CsV$_3$Sb$_5$中与笼目超导电性相关的低能电子结构提供了更清晰的实验图景。
英文摘要
Quantum interference encoded in the sublattice texture of kagome Bloch wavefunctions has been widely invoked as a route to correlated states, including chiral charge order, unconventional superconductivity, and their possible intertwining in pair-density-wave (PDW) states. Using sub-Kelvin scanning tunneling microscopy, we conducted spectroscopic mapping of the kagome material CsV$_3$Sb$_5$ with high energy resolution and dense energy sampling through the superconducting gap. Quasiparticle interference (QPI) analysis, aided by ab initio and symmetry calculations, reveals an isotropic superconducting gap on the Fermi surfaces derived from V $M_z$-even ($M_z^+$) $d$ orbitals, thereby constraining possible gap symmetries and limiting any gap anisotropy to the remaining V $M_z$-odd ($M_z^-$) and Sb $p_z$ bands. Meanwhile, the CDW-peak-selected d$I$/d$V$ spectra closely track the spatially averaged density of states and show no distinct enhancement restricted to subgap energies, which do not support an additional PDW modulation within our sensitivity. Finally, the selective absence of specific QPI scattering vectors points to a spectroscopic sensitivity to sublattice character on the Fermi surface. Together, these results provide a clearer experimental picture of the low-energy electronic structure relevant to kagome superconductivity in CsV$_3$Sb$_5$.
