Low-temperature heat capacity of nanostructured lead in porous glass

Abstract

We studied low-temperature specific heat capacity of 3D lead nanowires formed in porous glass with characteristic conductive network size d = 7 nm. The absolute value of the specific heat capacity increased in nanostructured lead compared to the bulk material, however its functional dependence on temperature remained virtually unchanged. The Debye temperature of nanostructured lead θ_D = 85 ± 2 K decreased compared to bulk lead value θ_D^bulk ≈ 87 К - 105 K, likely due to the softening of the phonon spectrum in nanostructured lead. The Sommerfeld constant also decreased in nanostructured lead γ = 7 ± 3 μJ g⁻¹ K⁻² compared to bulk lead γ^bulk = 15.1 μJ g⁻¹ K⁻², which is likely due to a change in the density of electronic states on the Fermi surface in the nanostructure. A jump in the temperature dependence of the heat capacity of nanostructured lead corresponding to the transition of lead nanofilaments to the superconducting state was recorded at a temperature T_c close to T_c^bulk for bulk lead. The amplitude of the superconducting transition jumps in the specific heat capacity of nanostructured lead decreased with increasing magnetic field. The temperature dependences of the specific heat capacity of electrons in the superconducting state for nanostructured lead are consistent with the Eliashberg theory for superconductors with strong coupling.