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Atomic manipulation of the gap in Bi2Sr2CaCu2O8+x


A major challenge in the study of high temperature superconductivity in copper oxide materials is to understand their macroscopic quantum behavior in terms of microscopic mechanisms. Using the electric field of a scanning tunneling microscope, researchers at the LPS have discovered a new approach to this problem. By moving individual atoms in the material they directly link the local atomic structure to the spectral gap.

A microscopic understanding of high temperature superconductors is one of the key open problems in condensed matter physics. Local probes, such as scanning tunneling microscopy, are ideally suited to tackle this problem due to their high spatial and energy sensitivity. However, the considerable disorder in copper oxide superconductors makes it challenging to extract to what extent the atomic structure is responsible for the remarkable electronic properties.

Using the electric field of the scanning tunneling microscope itself, researchers from the LPS discovered it is possible to selectively move individual atoms at the surface of one of the most studied high temperature superconductors, Bi2Sr2CaCu2O8+x. Since these single atom manipulations are non-invasive and reversible, they enable detailed studies of the electronic properties to be performed before and after manipulation. This technique therefore effectively removes the inhomogeneous environment and gives direct insight into the effect of single atoms on the electronic properties. They find that by moving bismuth atoms at the surface of Bi2Sr2CaCu2O8+x, the spectral gap that is associated with the local strength of superconductivity can be directly manipulated. This suggests that the single atoms locally enhance pairing, providing new insight into the pairing mechanism of these systems and the tunneling process into them.

Using the electric field of the tip of a scanning tunneling microscope, bismuth atoms at the surface of the high temperature superconductor Bi2Sr2CaCu2O8+x can be moved sideways. As a result of this single atom manipulation, the spectral gap is enhanced in the direction of the atomic shift.

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Freek Massee

Reference

Atomic manipulation of the gap in Bi2Sr2CaCu2O8+x
F. Massee, Y. K. Huang and M. Aprili
Science 367, 68-71 (2020)
https://doi.org/10.1126/science.aaw7964