Electronic Vortex Core Structure of d-Wave High Temperature Superconductors

High temperature superconductivity (HTS) in copper oxides keeps challenging our understanding. Among the outstanding puzzles is the electronic structure of the Abrikosov vortex cores. The fundamental excitations bound to magnetic vortices in type-II superconductors carry information about essential properties of the superconducting state. Their proper identification is therefore of prime interest to elucidate the mechanism driving HTS. We will review recent vortex core studies and present new scanning tunneling microscopy data [1] at low magnetic field, which unveil the d‑wave electronic structure of the vortex core predicted by Wang and MacDonald in 1995 [2]. We show that previously reported unconventional electronic structures, including the 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 inter-vortex distance and consequent vortex-vortex interactions prevailing in earlier experiments done at significantly higher field. The remarkable change of the spectroscopic footprint of the vortex cores we find between 0.16 Tesla and 3 Tesla is surprising for such a low energy scale and calls for further investigations.

[1] Gazdic, T., et al., arXiv:2103.05994, 2021.

[2] Y. Wang and A. H. MacDonald, Physical Review B 52, R3876 (1995).