Cooper Pair Density of Bi₂Sr₂CaCu₂O_8+x in Atomic scale at 4.2 K

Journal Article · 30 January 2019 · Nano Letters

DOI: https://doi.org/10.1021/acs.nanolett.8b04415 · OSTI ID:1504372

Joo, S. H.  ^[1]; Kim, J. -J. ^[1]; Yoo, J. H. ^[1]; Park, M. S. ^[1]; Lee, K. S. ^[1]; Gu, G. ^[2]; Lee, Jinho ^[1]

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1. Seoul National Univ. (SNU), Seoul (Republic of Korea); Center for Correlated Electron Systems, Seoul (Republic of Korea). Inst. for Basic Science (IBS)
2. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.

In pursuit of the elusive mechanism of high-T_C superconductors (HTSC), spectroscopic imaging scanning tunneling microscopy (SI-STM) is an indispensable tool for surveying local properties of HTSC. Since a conventional STM utilizes metal tips, which allow the examination of only quasiparticles and not superconducting (SC) pairs, Josephson tunneling using STM has been demonstrated by many authors in the past. An atomically resolved scanning Josephson tunneling microscopy (SJTM), however, was realized only recently on Bi₂Sr₂CaCu₂O_8+x (Bi-2212) below 50 mK and on the Pb(110) surface at 20 mK. Here we report the atomically resolved SJTM on Bi₂Sr₂CaCu₂O_8+x at 4.2 K using Bi-2212 tips created in situ. The I-V characteristics show clear zero bias conductance peaks following Ambegaokar-Baratoff (AB) theory. A gap map was produced for the first time using an atomically resolved Josephson critical current map I_C(r) and AB theory. Surprisingly, we found that this new gap map is anticorrelated to the gap map produced by a conventional method relying on the coherence peaks. Quasiparticle resonance due to a single isolated zinc atom impurity was also observed by SJTM, indicating that atomically resolved SJTM was achieved at 4.2 K. Lastly, our result provides a starting point for realizing SJTM at even higher temperatures, rendering possible investigation of the existence of SC pairs in HTSC above the T_C.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012704
• OSTI ID: 1504372
• Report Number(s): BNL-211487-2019-JAAM
• Journal Information: Nano Letters, Vol. 19, Issue 2; ISSN 1530-6984
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English