Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

Specific temperature dependence of pseudogap in YBa₂Cu₃O_7-δ nanolayers

A. L. Solovjov

B. Verkin Institute for Low Temperature Physics and Engineering, NAS of Ukraine, Kharkov

After just 30 years since the high-T_c superconductors discovery pseudogap (PG) remains their main puzzle. PG is believed to be due to paired fermions formation. But the coupling mechanism, which allows the pairing at very high T above T_c is very likely of the magnetic type. The interplay between superconductivity and magnetism is one of the challenging problem of the high-temperature superconductivity now.

Study of YBa₂Cu₃O_7-δ-PrBa₂Cu₃O_7-δ (YBCO-PrBCO) superlattices (SL's) and double-layer films - “sandwiches” (SD's) is to clarify the issue. It is because Pr has its intrinsic magnetic moment ~4 mu(B) and ~ 2 mu(B) as PrBCO, and magnetic influence in these compounds has to increase along with increase of the number of the Pr layers (N_pr). Besides, very thin but homogeneous YBCO layers, imbedded into the PrBCO matrix, can be investigated.

The study has shown two noticeable features which have not been observed in nonmagnetic superconductors. First is the enhanced Maki-Thompson fluctuation contribution into excess conductivity σ'(T)= σ(T) –σ_N(T)= 1/ρ(T)- 1/ρ_N(T), measured as a difference between longitudinal resistivity ρ(T) and the linear normal-state resistivity ρ_N(T) = ρ₀ + αТ extrapolated towards low T region.

Second is the unusual temperature dependence of the PG with pronounced maximum at high temperatures being typical for magnetic FeAs-based superconductors.

Thus, one may conclude that the basic mechanism of the interplay between the superconductivity and magnetism is to be the same in the all superconductors in which superconductivity can coexist with magnetism.