RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan.
Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
Phys Rev Lett. 2019 Feb 22;122(7):077001. doi: 10.1103/PhysRevLett.122.077001.
FeSe is argued as a superconductor in the Bardeen-Cooper-Schrieffer Bose-Einstein condensation crossover regime where the superconducting gap size and the superconducting transition temperature T_{c} are comparable to the Fermi energy. In this regime, vortex bound states should be well quantized and the preformed pairs above T_{c} may yield a pseudogap in the quasiparticle-excitation spectrum. We performed spectroscopic-imaging scanning tunneling microscopy to search for these features. We found Friedel-like oscillations near the vortex, which manifest the quantized levels, whereas the pseudogap was not detected. These apparently conflicting observations may be related to the multiband nature of FeSe.
FeSe 在 Bardeen-Cooper-Schrieffer Bose-Einstein 凝聚交叉区被认为是超导体，其中超导能隙大小和超导转变温度 Tc 与费米能相当。在这个区域，涡旋束缚态应该被很好地量子化，而在 Tc 以上的预形成对可能会在准粒子激发谱中产生赝能隙。我们进行了光谱成像扫描隧道显微镜来寻找这些特征。我们在涡旋附近发现了类似于 Friedel 的振荡，这表明了量子化的能级，而赝能隙则没有被检测到。这些明显相互矛盾的观察结果可能与 FeSe 的多带性质有关。
