Magnetic superconductors

Abstract

Valence-band and conduction-band densities of states (DOSs) of trigonal and amorphous Se have been investigated by in situ measurements of ultraviolet photoemission and inverse-photoemission spectroscopies (UPS and IPES), respectively. The IPES spectra reveal, for the first time, a measure of conduction-band DOS, while the UPS spectra are fully consistent with earlier results. From comparison between theoretical DOS and a whole spectrum for trigonal Se obtained by a connection of the UPS and IPES spectra at the Fermi level, it has been shown that the coupling strength between the hybrid 4p-like orbitals of different atoms should be increased. On the basis of a comparison between IPES and core-absorption spectra for trigonal Se, a prominent peak and weak structures in the 1-5 and 5-10 eV regions above the valence-band maximum in the IPES spectrum are experimentally assigned to the 4p-like antibonding and 4d and/or 5s states, respectively. In amorphous Se, the peak at shallower energy in the 4p-like bonding bands with two peak structures is more intense in contrast to the case of the trigonal one. Such a change is attributed to a chain structure with the dihedral angle varying randomly in sign along the chain. Increases of the bonding-antibonding splitting energy of the 4p-like bands and band-gap energy in amorphous Se are ascribed to an increase of intrachain coupling strength between the hybrid 4p-like orbitals and a simultaneous decrease of the interchain coupling strength. † Present address:

Possible existence of superconductivity in the quasi-one-dimensional conductorLi0.9Mo6O17at ultrahigh magnetic fields (Lebed1 2016Phys. Rev. B0000View full textAdd to dashboardCite

“…Nevertheless, we pay attention that there are two main important differences between our results and the results of Refs. [27,28]. First of all, we consider Q1D superconductor in a magnetic field, parallel to its conducting axis, whereas in Refs.…”

“…(24) from very general Eq. (14) -not from phenomenological LawrenceDoniach model [27,28]. Note that Mathieu equation (24) is studied in details in the existing literature (see, for example, Refs.…”

“…(14) contains several different limiting cases for the different regions of its parameters. First of all, for low magnetic fields, it reduces to the Ginzburg-Landau equation [26] and this limiting case will be considered below as a part of more general Lawrence-Doniach-like description [27,28]. At extremely high magnetic fields, where…”

“…First of all, we consider Q1D superconductor in a magnetic field, parallel to its conducting axis, whereas in Refs. [27,28] only a Q2D superconductor is studied. Second, we have derived Eq.…”

“…Note that Mathieu equation (24) is studied in details in the existing literature (see, for example, Refs. [27,28].) In the near vicinity of superconducting transition temperature, (…”