Visualizing the Energy-gap Modulations of the Cuprate Pair Density Wave State
| Autor: | Du, Zengyi, Li, Hui, Joo, Sanghyun, Donoway, Elizabeth P., Lee, Jinho, Davis, J. C., Gu, Genda, Johnson, Peter D., Fujita, Kazuhiro |
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| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Nature 580, 65 (2020) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1038/s41586-020-2143-x |
| Popis: | When Cooper pairs are formed with finite center-of-mass momentum, the defining characteristic is a spatially modulating superconducting energy gap $\Delta(r)$. Recently, this concept has been generalized to the pair density wave (PDW) state predicted to exist in a variety of strongly correlated electronic materials such as the cuprates. Although the signature of a cuprate PDW has been detected in Cooper-pair tunnelling, the distinctive signature in single-electron tunneling of a periodic $\Delta(r)$ modulation has never been observed. Here, using a new approach, we discover strong $\Delta(r)$ modulations in Bi$_2$Sr$_2$CaCu$_2$O$_8$+$\delta$ that have eight-unit-cell periodicity or wavevectors $Q=2{\pi}/a_0(1/8,0)$; $2{\pi}/a_0(0,1/8)$. This constitutes the first energy-resolved spectroscopic evidence for the cuprate PDW state. An analysis of spatial arrangements of $\Delta(r)$ modulations then reveals that this PDW is predominantly unidirectional, but with an arrangement of nanoscale domains indicative of a vestigial PDW. Simultaneous imaging of the local-density-of-states $N(r,E)$ 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 discover them to be concentrated in areas where the PDW spatial phase changes by $\pi$, as predicted by the theory of half-vortices in a PDW state. Overall, this is a compelling demonstration, from multiple single-electron signatures, of a PDW state coexisting with superconductivity at zero magnetic field, in the canonical cuprate Bi$_2$Sr$_2$CaCu$_2$O$_8$+$\delta$. Comment: Final submitted version. arXiv admin note: text overlap with arXiv:2109.14031 |
| Databáze: | arXiv |
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