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Imaging the energy gap modulations of the cuprate pair-density-wave state

Cornell Affiliated Author(s)

Author

Z. Du
H. Li
S.H. Joo
E.P. Donoway
J. Lee
J.C.S. Davis
G. Gu
P.D. Johnson
K. Fujita

Abstract

The defining characteristic1,2 of Cooper pairs with finite centre-of-mass momentum is a spatially modulating superconducting energy gap Δ(r), where r is a position. Recently, this concept has been generalized to the pair-density-wave (PDW) state predicted to exist in copper oxides (cuprates)3,4. Although the signature of a cuprate PDW has been detected in Cooper-pair tunnelling5, the distinctive signature in single-electron tunnelling of a periodic Δ(r) modulation has not been observed. Here, using a spectroscopic technique based on scanning tunnelling microscopy, we find strong Δ(r) modulations in the canonical cuprate Bi2Sr2CaCu2O8+δ that have eight-unit-cell periodicity or wavevectors Q ≈ (2π/a0)(1/8, 0) and Q ≈ (2π/a0)(0, 1/8) (where a0 is the distance between neighbouring Cu atoms). Simultaneous imaging of the local density of states N(r, E) (where E is the energy) reveals electronic modulations with wavevectors Q and 2Q, as anticipated when the PDW coexists with superconductivity. Finally, by visualizing the topological defects in these N(r, E) density waves at 2Q, we find them to be concentrated in areas where the PDW spatial phase changes by π, as predicted by the theory of half-vortices in a PDW state6,7. Overall, this is a compelling demonstration, from multiple single-electron signatures, of a PDW state coexisting with superconductivity in Bi2Sr2CaCu2O8+δ. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.

Date Published

Journal

Nature

Volume

580

Issue

7801

Number of Pages

65-70,

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083067516&doi=10.1038%2fs41586-020-2143-x&partnerID=40&md5=12b195ffee0eccaee5a1eaf63a6e6819

DOI

10.1038/s41586-020-2143-x

Group (Lab)

J.C. Seamus Davis Group

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