arXiv subjects

Hércules Santana

Publications and source records attributed to Hércules Santana.

2 recordsLinked to original sources

arXiv2024

The role of the pseudogap in cuprate superconductors revealed by the Hall effect

Cuprate high-temperature superconductors are known to have a normal-state pseudogap but, after many years of intense research, its relation to the superconductivity is still a mystery. Similarly, the in-plane Hall coefficient $R_{\rm H}$ has a large temperature variation caused by changes in the carrier density which is also a long-standing puzzle. We approach both problems by a kinetic theory of phase separation that reproduces the charge density wave by a free energy array of potential wells. The charge modulation favors local hole-hole attraction yielding local superconducting pairs and a transition by long-range phase order at $T_{\rm c}$. As the temperature increases the modulations decrease and the charge density increases by thermal activation. This approach reproduces the $R_{\rm H}$ of La$_{2-x}$Sr$_x$CuO$_4$ compounds of $x = 0.0 - 0.25$ and clarifies the role of the pseudogap and the disorder in cuprates.

cond-mat.supr-con↗

arXiv2023

Generalization of interlayer tunneling models to cuprate superconductors with charge density waves

At the beginning of cuprate superconductors, the interlayer tunneling (ILT) and Lawrence-Doniach (L-D) models, which connect the CuO planes by Josephson coupling were considered the leading theoretical proposals for these materials. However, measurements of the interlayer magnetic penetration depth $λ_{c}$ yielded larger values than required by the ILT model. After the discovery of planar stripes and incommensurate charge ordering, it was also possible to consider Josephson coupling between these mesoscopic charge domains or blocks. We show that the average intralayer is larger than the interlayer coupling and comparable with the condensation energy, leading to a superconducting transition by long-range phase order. Another consequence is that the ratio $[λ_{c}/λ_{ab}]^2$ is directly proportional resistivity ratio $ρ_c/ ρ_{ab}$ near the superconducting transition temperature in agreement with several measurements.

cond-mat.supr-con↗