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ID 33925
file
creator
Shohara, Kazuhiro
Zheng, Zhanfeng
NDC
Physics
abstract
Scanning tunneling microscopy and spectroscopy (STM-STS) measurements have been carried out on the α (FeOCl)–type KxTiNCl (x∼0.5, Tc=16 K) and β (SmSI)–type HfNCly (y∼0.7, Tc=24 K) layered nitride superconductors. The STM images at 5 K showed clear atomic arrangements for both the compounds, namely, the rectangular lattice on α-KxTiNCl and the triangular lattice on β-HfNCly. The tunneling spectra in the superconducting states at low temperatures demonstrate qualitatively different features between these superconductors. For α-KxTiNCl, the spatial distributions of the density of states and the superconducting gap structures are very inhomogeneous, while those on β-HfNCly are found to be almost homogeneous. The nanoscale electronic features between these compounds correlate with the different lattice structures of the M (=Ti or Hf) N conducting layers, which are caused by the lattice symmetry difference itself or induced by the difference in the local doping distributions in these chemically reactive compounds. The averaged gap magnitudes in the superconducting states, Δ̅ ≃10.2 meV and 7.5 meV for α-KxTiNCl and β-HfNCly, corresponding to the gap ratios 2Δ̅ /kBTc≃ 15 and 7.2, respectively, indicate the unusually strong coupling effects of the superconductivity.
journal title
Physical Review B
volume
Volume 85
issue
Issue 14
start page
144517
date of issued
2012
publisher
American Physical Society
issn
1098-0121
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
(c) 2012 American Physical Society
relation url
department
Graduate School of Integrated Arts and Sciences
Graduate School of Engineering