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We have developed a number of new techniques based on variable temperature scanning tunneling microscopy/spectroscopy to visualize pair formation in BiSrCaCuO [1] and probe its origin [2] on the nanometer scale in this compound. These experiments show that pairing occurs in small "puddles" that originate above the transition temperature Tc over a range of temperatures and that the local strength of pairing is controlled by unusual asymmetric electron-hole excitation of the normal state. In addition, these experiments address the relevance of so-called electron boson coupling (seen in number of different spectroscopic experiments over the years) to determine its connection with the local strength of pairing.
[1] Gomes et al. Nature V447, 569 (2007). [2] Pasupathy et al. Science V320, 196 (2008). |
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