arXiv subjects

L. S. Mazov

Publications and source records attributed to L. S. Mazov.

5 recordsLinked to original sources

arXiv2015

Comment on "Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system" (A. P. Drozdov et al., Nature 525, 73 (2015))

It is demonstrated that resistive transition at 203 K observed in metallic sulfur hydride system at high pressure can be magnetic (rather than superconducting (SC)) in nature. The onset temperature of genuine superconducting transition in these compounds appears to be essentially lower on temperature. The normal-state magnetic (AF SDW) phase transition preceding a superconducting one (Tc < Tm) is characteristic for HTSC cuprates, pnictides (selenides) and organic superconductors. The resistive drop is provided by disappearing of magnetic (AF spin fluctuation) scattering of conduction electrons and hence formation of AF SDW order in the normal state. The formation of such modulated magnetic structure in sulfur hydride seems to be possible because of magnetic properties of metallic hydrogen at high densities (in analogy with iron). Such unconventional picture with two successive phase transitions: magnetic (AF SDW) and only then superconducting one is naturally described by Keldysh-Kopaev theory of dielectric (metal-insulator) phase transition in systems with coexistence of superconducting (e-e) and dielectric (e-h)pairings.

cond-mat.supr-con↗

arXiv2009

HTSC-glue in doped copper oxides and iron pnictides: mobile CT-excitons within in-plane Ginzburg HTSC-sandwich

It is demonstrated that high critical temperature of superconducting transition in cuprates and new iron-based superconductors is reached because of the Little-Ginzburg exciton mechanism of HTSC when Cooper pairing of mobile charge carriers is mediated by excitons which characteristic energy is essentially higher than Debye one for phonons. The effectiveness of such mechanism in these doped compounds is provided due to a series of planar Ginzburg HTSC-'sandwiches': 'insulator'-'metal'- 'insulator' (stripe structure) naturally forming in conducting planes below the onset pseudogap temperature in the normal state. The parameters of mobile, planar charge-transfer (CT) excitons in outer 'insulating' plates of such in-plane HTSC-'sandwich' are exactly within the optimal range predicted by Ginzburg about forty years ago.

cond-mat.supr-con↗

arXiv2008

On superconducting mechanism in the iron-based layered superconductors

It is demonstrated that SC mechanism of doped Fe-based compounds is characteristic for itinerant electron systems with coexistence of both (e-e)- and (e-h)-pairing arising due to electron-phonon and Coulomb interactions, respectively. The higher Tc of the SC transition here (as compared with conventional (LTSC) BCS-systems without (e-h)-pairing) is a natural consequence of (e-e)-pairing at the background of high density of states which arises in the narrow energy range near dielectric-(SDW)-gap (pseudogap) edges due to removing of electronic states from the energy region of dielectric (SDW) gap (pseudogap) (already formed at the part of the Fermi surface in the normal state with onset temperature T* (near the same for corresponding structural transition) due to (e-h)-pairing). Below Tc the system enters the coexistence (SC+SDW) state. The SDW formed is incommensurate with lattice and dynamic in character. The phase diagram for such system is determined: the doping dependence of the SC gap (and Tc) has a maximum (optimal doping) while the dielectric (SDW) gap (pseudogap) (and T*) is a decreasing function of doping. These conclusions follow from detailed analysis of available resistivity and another data for Fe-based superconductors on the basis of model with partial dielectrization of electron energy spectra. The picture obtained and manifestation of two order parameters (SC and SDW) in experiments, first of all, in threshold phenomena are discussed. The comparison with the case of cuprates is performed.

cond-mat.supr-con↗

arXiv2002

Spin density wave and pseudogap in HTSC cuprates

The evidence for the spin density wave (SDW) nature of the pseudogap in HTSC cuprates is presented from resistive and direct gap measurements (ARPES, tunneling experiments, etc.). Its d-wave symmetry mimics the symmetry of the order parameter measured in the SC state. The magnetic phase $H-T$ diagram for HTSC cuprates is formed. The possible influence of an additional (SDW) order parameter on the vortex structure in the applied magnetic field is analysed. The behavior is discussed in terms of itinerant electron systems with interplay between superconductivity and magnetism.

cond-mat.supr-con↗

arXiv2001

To the problem of electron-phonon interaction and "d-wave pairing" in high-Tc oxides

It is supported a recent proposal by Maksimov that electron-phonon interaction (EPI) (Gruneisen-Bloch formulae) determines the linearity of temperature dependence of resistivity for both HTSC-cuprates and most of metals at T near above 0.2 of their characteristic Debye temperature (normal state for HTSC). However, it is emphasized here that in this T-region the resistivity is not proportional to T but is only linear in T. This fact indicates to T-independent contribution to normal-state resistivity in HTSC-cuprates (magnetic contribution, in our treatment) which behavior, in its turn, indicates to possible magnetic (SDW-like) phase transition before SC transition in HTSC-system. SDW-gap (measured as pseudogap with d-wave symmetry, in our treatment) is formed at the symmetrical parts of the Fermi surface above Tc and persists in SC state. The magnitude of SDW-gap is essentially larger than that for SC-gap. So, SDW formed can mimic d-wave symmetry of the order parameter measured below Tc (which is now attributed to d-wave pairing). On the other hand, since the Gruneisen-Bloch curve appears to be (in approach used) a geometric locus for the Tc(onset)(H) (as in LTSC) this fact evidents about EPI-nature (BCS) of SC transition (s-wave) in high-Tc oxides. The proposal to increase Tc using above (SDW/CDW/SC) model (and possible realization) is presented.

cond-mat.supr-con↗