English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Nuclear quadrupole resonance (NQR) on copper nuclei has been applied forstudies of the electronic properties of quasi-two-dimensional low-temperaturesuperconductor CuS (covellite) in the temperature region between 1.47 and 290K. Two NQR signals corresponding to two non-equivalent sites of copper in thestructure, Cu(1) and Cu(2), has been found. The temperature dependences ofcopper quadrupole frequencies, line-widths and spin-lattice relaxation rates,which so far had never been investigated so precisely for this material,altogether demonstrate the structural phase transition near 55 K, whichaccompanies transformations of electronic spectrum not typical for simplemetals. The analysis of NQR results and their comparison with literature datashow that the valence of copper ions at both sites is intermediate in characterbetween monovalent and divalent states with the dominant of the former. It hasbeen found that there is a strong hybridization of Cu(1) and Cu(2) conductionbands at low temperatures, indicating that the charge delocalization betweenthese ions takes place even in 2D regime. Based on our data, the occurrence ofenergy gap, charge fluctuations and charge-density waves, as well as the natureof phase transition in CuS are discussed. It is concluded that some physicalproperties of CuS are similar to those of high-temperature superconductors(HTSC) in normal state.

Phase transition and anomalous electronic behavior in layered dichalcogenide CuS (covellite) probed by NQR