Abstract
Low-magnetic-field scanning tunneling spectroscopy of individual Abrikosov vortices in heavily overdoped unveils a clear -wave electronic structure of the vortex core, with a zero-bias conductance peak at the vortex center that splits with increasing distance from the core. We show that previously reported unconventional electronic structures, including the low-energy checkerboard charge order in the vortex halo and the absence of a zero-bias conductance peak at the vortex center, are direct consequences of short intervortex distance and consequent vortex-vortex interactions prevailing in earlier experiments.
- Received 16 February 2021
- Revised 29 April 2021
- Accepted 17 June 2021
DOI:https://doi.org/10.1103/PhysRevX.11.031040
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Magnetic vortices in superconductors are singular objects at the center of which the superconducting Cooper pairs of electrons are locally destroyed. As a consequence, the electronic excitations in their cores are expected to be fundamentally different from the ones occurring in the electronic superfluid surrounding the vortices. Scanning tunneling microscopy is the ideal tool to study these singular states, whose spectroscopic signatures are predicted to carry essential information about the intrinsic nature of the superconducting state. While vortex cores of “conventional” low-temperature superconductors are understood in great detail, past experiments revealed very unusual electronic vortex core structures in high-temperature superconductors not compatible with theory. Now, exploring vortices in a high-temperature superconductor using scanning tunneling microscopy at unprecedentedly low magnetic fields, we reveal their genuine electronic structure, which turns out to be consistent with a 25-year-old theoretical model.
Previous experiments showed that in the vicinity of a vortex, the electronic states were spatially modulated over a four-unit-cell distance, forming a checkerboard pattern. At the low magnetic field we use, this checkerboard is no longer observed. Moreover, precisely in the vortex center, we measure a single conductance peak that splits into two peaks with increasing distance from the vortex core. This behavior, which was never reported at high magnetic fields, is precisely the one predicted by Wang and MacDonald for a superconductor whose Cooper pairs’ wave functions are anisotropic in momentum space (known as -wave symmetry).
The proper identification of these vortex core states is of prime interest to elucidate the mechanism driving high-temperature superconductivity, which still remains unclear.