Properties of the nearly free electron superconductor Ag5Pb2O6 inferred from Fermi surface measurements

Abstract

We measured the Fermi surface of the recently discovered superconductor Ag5Pb2O6 via a de Haas-van Alphen rotation study. Two frequency branches were observed and identified with the neck and belly orbits of a very simple, nearly free electron Fermi surface. We use the observed Fermi surface geometry to quantitatively deduce superconducting properties such as the in-plane and out-of-plane penetration depths, the coherence length in the clean limit, and the critical field; as well as normal state properties such as the specific heat and the resistivity anisotropy.

Transport properties of Ag5Pb2O6: A three-dimensional electron-gas-like system with low carrier density

“…Indeed, in many metals, resistivity is found to saturate to a value close to ρ MIR at sufficiently high temperatures, in clear contrast to the prediction of ρ ∝ T based on the high-temperature Boltzmann theory. For Ag 5 Pb 2 O 6 , the MIR limit is estimated as ρ MIR ∼ 730 µΩcm, based on the values k F = 0.53 Å −1 determined from the quantum oscillation experiment 20,21 and d ∼ a = 5.93 Å. 18 Therefore, ρ c of Ag 5 Pb 2 O 6 is still smaller than the MIR limit in the present temperature range, manifesting the validity of semiclassical treatments of transport phenomena.…”

“…As another estimation of r s , we use the relation r s = (αk F a B ) −1 and quote the value k F = 0.53 Å −1 determined by quantum oscillations. 20,21 Then, we obtain r s = 6.8. Furthermore, if we use a * B ≡ (4πε 0 2 )/(m * e e 2 ) with the effective electron mass m * = 1.2m e (Ref.…”

“…We discovered the ambient-pressure superconductivity of this oxide below T c = 52 mK by the resistivity and AC susceptibility measurements. 23,24 The band structure calculation 19 and the quantum oscillation experiment 20,21 revealed that Ag 5 Pb 2 O 6 has a nearly spherical "free-electron like" Fermi surface as shown in Fig. 1(c), despite its apparent layered structure.…”