Four-fold structure of vortex core states in Bi₂Sr₂CaCu₂O₈ (Bi2212)

Giorgio Levy, Martin Kugler, Alfred A. Manuel, and Øystein Fischer
DPMC, Université de Genève, 24 Quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland

Ming Li
Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9506, 2300 RA Leiden, The Netherlands

We present a detailed study of vortex core spectroscopy in slightly overdoped Bi2Sr2CaCu2O8 (Bi2212) using a low temperature scanning tunneling microscope. Inside the vortex core we observe a four- fold symmetric modulation of the local density of states with an energy-independent period of(4.3 ±0.3)a0. Furthermore we demonstrate that this square modulation is related to the vortex core states which are located at ~6 meV. Since the core-state energy is proportional to the supercon-ducting gap magnitude Δp, our results strongly suggest the existence of a direct relation between the superconducting state and the local electronic modulations in the vortex core.