Superconductors are of type I or II depending on whether they form an Abrikosov vortex lattice. Although bulk lead (Pb) is classified as a prototypical type-I superconductor, we show that its two-band superconductivity allows for single-flux-quantum and multiple-flux-quanta vortices in the intermediate state at millikelvin temperature. Using scanning tunneling microscopy, the winding number of individual vortices is determined from the real space wave function of its Caroli-de Gennes-Matricon bound states. This generalizes the topological index theorem put forward by Volovik for isotropic electronic states to realistic electronic structures. In addition, the bound states due to the two superconducting bands of Pb can be separately detected and the two gaps close independently inside vortices. This yields strong evidence for a low interband coupling.
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http://dx.doi.org/10.1126/sciadv.adh9163 | DOI Listing |
Nano Lett
October 2024
Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, PR China.
The noble metal alloy AuSn has recently been identified as an intrinsic surface topological superconductor, promisingly hosting the Majorana zero mode (MZM) for topological quantum computing. However, the atomic visualization of its nontrivial surface states and MZM remains elusive. Here, we report the direct observation of unconventional surface states and vortex zero mode in AuSn by scanning tunneling microscopy/spectroscopy.
View Article and Find Full Text PDFJ Phys Condens Matter
October 2024
Laboratorio de Bajas Temperaturas y Altos Campos Magnéticos, Departamento de Física de la Materia Condensada. Instituto Nicolás Cabrera and Unidad Asociada UAM-CSIC, Universidad Autónoma de Madrid, E28049 Madrid, Spain.
We provide the superconducting density of states of the pnictide superconductor LaRuP(= 4.1 K), measured using millikelvin scanning tunneling microscopy. From the tunneling conductance, we extract a density of states which shows the opening of a s-wave single superconducting gap.
View Article and Find Full Text PDFSci Bull (Beijing)
April 2024
Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China; Hefei National Laboratory, Hefei 230088, China. Electronic address:
Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors. Recently, surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsVSb. Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states, its origin remains elusive.
View Article and Find Full Text PDFSci Adv
September 2023
Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str.1, 76131 Karlsruhe, Germany.
Superconductors are of type I or II depending on whether they form an Abrikosov vortex lattice. Although bulk lead (Pb) is classified as a prototypical type-I superconductor, we show that its two-band superconductivity allows for single-flux-quantum and multiple-flux-quanta vortices in the intermediate state at millikelvin temperature. Using scanning tunneling microscopy, the winding number of individual vortices is determined from the real space wave function of its Caroli-de Gennes-Matricon bound states.
View Article and Find Full Text PDFJ Phys Condens Matter
January 2023
Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
By solving the Bogoliubov-de Gennes equations for a-wave superconductor, we explore how the interplay between disorder and the orbital depairing of an external magnetic field influences the superconductor-metal transition of the hole-overdoped cuprates. For highly disordered systems, we find granular Cooper paring to persist above the critical field where the superfluid stiffness goes to zero. We also show that because the vortices are attracted to regions where the superconducting pairing is already weak, the Caroli-de Gennes-Matricon zero-bias peak in the local density of states at the vortex cores disappears already at moderate disorder.
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