摘要
Here we report a TiHfNbTa bulk medium-entropy alloy(MEA)superconductor crystallized in the body-centered cubic structure with the unit cell parameter a=3.35925?,which is synthesized by an arc melting method.Superconducting properties of the TiHfNbTa are studied by employing magnetic susceptibility,resistivity,and specific heat measurements.Experimental results show a bulk superconducting transition temperature(Tc)of around 6.75 K.The lower and upper critical fields for TiHfNbTa are45.8 m T and 10.46 T,respectively.First-principles calculations show that the d electrons of Ti,Hf,Nb,and Ta are the main contribution to the total density of states near the Fermi level.Our results indicate that the superconductivity is a conventional swave type with extremely strong coupling(△C_(el)/γ_(n)T_(c)=2.88,2△_(0)/k_(B)T_(c)=5.02,and λ_(ep)=2.77).The extremely strong coupling behavior in the s-wave type Ti Hf Nb Ta MEA superconductor is unusual because it generally happens in cuprates,pnictides,and other unconventional superconductors.
基金
supported by the National Natural Science Foundation of China(Grant Nos.12274471,and 11922415)
the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022A1515011168,and 2019A1515011718)
the Key Research and Development Program of Guangdong Province,China(Grant No.2019B110209003)
supported by the Foreign Young Talents Program of China(Grant No.22KW041C211)
supported by the Key-Area Research and Development Program of Guangdong Province(Grant No.2020B0101340002)
supported by the NKRDPC(Grant Nos.2022YFA1402802,and 2018YFA0306001)
the National Natural Science Foundation of China(Grant Nos.11974432,and 92165204)
the Leading Talent Program of Guangdong Special Projects(Grant No.201626003)
the Shenzhen International Quantum Academy(Grant No.SIQA202102)。
