Paramagnetic spin splitting of the conductances for tunnel junctions between partiallygapped metals with charge density waves and normal metals or ferromagnets

Abstract

We consider tunnelling between a metal partially gapped by charge density waves (CDWM) and anordinary metal (M) or a ferromagnet (FM) separated by an insulator (I) in an external magnetic fieldH. Zeeman paramagnetic splitting is assumed to dominate in theCDWM over orbital magnetic effects. The quasiparticle tunnel currentJ and relevantdifferential conductance G are calculated as functions of the bias voltageV. Thepeaks of G(V), originating from the electron density of states singularities near the chargedensity wave gap edges, were shown to be split in the magnetic field, eachpeak having a predominant spin polarization. This effect is analogous to theH-inducedsplitting of G(V) peaks obtained by Tedrow and Meservey for junctions between normal metalsand superconductors (S). Thus, it is possible to electrically measure thepolarization of current carriers in such a set-up, although the behaviours ofG(V) in the two cases are substantially different. The use of M–I–CDWM junctions instead ofM–I–S ones has certain advantages. The absence of the Meissner effect, which weakensthe constraints upon the junction geometry and electrode materials, comprisesthe main benefit. The other advantage is the larger energy range of the chargedensity wave gaps in comparison to that for superconductors’ gaps, so that largerHs may be applied.