STM Maps Granular Structure of Superconductivity at Nanoscale Level
- PDF / 843,457 Bytes
- 2 Pages / 612 x 792 pts (letter) Page_size
- 58 Downloads / 171 Views
magnetic resonant mode below Tc . Constant-energy scans show the mode at an energy of 47 meV, somewhat larger than the previously reported 40-meV mode energies in the bilayer compounds. JENNIFER BURRIS
STM Maps Granular Structure of Superconductivity at Nanoscale Level Researchers at Lawrence Berkeley National Laboratory and the University of California, Berkeley, have used scanning tunneling microscopy (STM) to make nanometer-scale maps of “granular” superconductivity in the high-temperature superconductor Bi-2212 (Bi2Sr2CaCu2O8+δ). They verified their discovery with a second use of STM, employing individual nickel atoms as dopant probes to distinguish superconducting from nonsuperconducting regions in Ni-doped Bi-2212. J.C. Séamus Davis, a researcher with LBNL’s
MRS BULLETIN/APRIL 2002
Materials Sciences Division and a professor of physics at UC—Berkeley, and his colleagues have shown that a high-Tc superconductor with what is believed to be an essentially perfect crystal structure can exhibit granular superconductivity, (regions of superconductivity spatially separated from one another). As reported in the January 24 issue of Nature, Davis’s group cleaved perfect single crystals of B-2212, which split cleanly along the bismuth-oxygen plane lying immediately over the copper-oxygen plane. Using STM, the researchers were able to image individual atoms in the plane. In ultrahigh vacuum at very low temperature, the electronic states of the underlying copper-oxygen plane could also be sensed. As the probe tip scanned over the plane, it measured differences in the current reaching the tip. Two kinds of regions of different conductance were
revealed: α regions exhibiting relatively small energy gaps, typical of superconductivity; and β regions with larger gaps. From these spectral scans, “gapmaps” were constructed, showing that in the underdoped crystal, the α regions were roughly circular areas
Data Loading...
