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

Specific heat can explore low-energy quasiparticle excitations ofsuperconductors, so it is a powerful tool for bulk measurement on thesuperconducting gap structure and pairing symmetry. Here, we report an in-depthinvestigation on the specific heat of the multiband superconductorsKCa$_2$(Fe$_{1-x}$Ni$_x$)$_4$As$_4$F$_2$ ($x$ = 0, 0.05, 0.13) single crystalsand the overdoped non-superconducting one with $x$ = 0.17. Clear specific heatanomalies can be observed at the superconducting transition temperature of 33.6K and 28.8 K for the samples with $x$ = 0 and $x$ = 0.05, respectively. For thetwo samples, the magnetic field induced specific heat coefficient$\Delta\gamma(H)$ in the low-temperature limit increases rapidly below 2 T,then it rises slowly above 2 T. Using the non-superconducting sample with $x$ =0.17 as a reference, the specific heat of phonon background for varioussuperconducting samples can be obtained and subtracted, which allows us toextract the electronic specific heat of the superconducting samples. Throughcomparative analyses, it is found that the energy gap structure including two$s$-wave gaps and an extended $s$-wave gap with large anisotropy can reasonablydescribe the electronic specific heat data. According to these results, wesuggest that at least one anisotropic superconducting gap with a deep gapminimum should exist in this multiband system. With the doping of Ni, thesuperconducting transition temperature of the sample decreases along with thedecrease of the large $s$-wave gap, but the extended $s$-wave gap increases dueto the enlarged electron pockets via adding more electrons. Despite thesechanges, the general properties of the gap structure remain unchanged versusdoping Ni.

Multiband superconductivity and a deep gap minimum from the specific heat in KCa$_2$(Fe$_{1-x}$Ni$_x$)$_4$As$_4$F$_2$ ($x$ = 0, 0.05, 0.13)