Anomalous electron-phonon coupling probed on the surface of superconductor ZrB12

Article

关键词: MAGNETIC PENETRATION DEPTH;    LATTICE-VIBRATIONS;    TEMPERATURE;   

DOI  :  10.1103/PhysRevB.72.224509

来源: SCIE

【 摘 要 】

Magnetization measurements under hydrostatic pressure up to 10.5 kbar in zirconium dodecaboride ZrB12 superconductor (T-c similar or equal to 6.0 K at p=0) were carried out. A negative pressure effect on T-c with dT(c)/dp=-0.0225(3) K/kbar was observed. The electron-phonon coupling constant lambda(el-ph) decreases with increasing pressure with d ln lambda(el-ph)/dp similar or equal to-0.20%/kbar. The magnetic field penetration depth lambda was studied in the Meissner state and, therefore, probes mainly the surface of the sample. The absolute values of lambda and the superconducting energy gap at ambient pressure and zero temperature were found to be lambda(0)=140(30) nm and Delta(0)=1.251(9) meV, respectively. Delta(0) scales linearly with T-c as 2 Delta(0)/k(B)T(c)=4.79(1). The studies of the pressure effect on lambda reveal that lambda(-2) increases with pressure with d ln lambda(-2)(0)/dp=0.60(23)%/kbar. This effect cannot be explained within the framework of conventional adiabatic electron-phonon pairing, suggesting the possibility that close to the surface an unconventional nonadiabatic character of the electron-phonon coupling takes place.

【 授权许可】

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