ON TUNNEL SPECTROSCOPY OF NORMAL METALS WITH CHARGE-DENSITY OR SPIN-DENSITY WAVES

Current-voltage (I-V) characteristics of the tunnel current J across symmetrical and nonsymmetrical tunnel junctions, which use for plates metals with charge- or spin-density waves and the dielectric gap Sigma on the Fermi surface sections, are calculated. Far the symmetrical (s) junction the I-V characteristic is antisymmetrical about a bias V and does not depend on the sign of Sigma. The dependence J(s)(V) involves the square root singularity for \eV\ = \Sigma\ and the inflection for \eV\ = 2\Sigma\. The I-V characteristic of the nonsymmetrical (ns) junction depends on the sign of Sigma. Different terms in J(ns)(V) have different symmetry properties with respect to the replacement V -> - V. As a whole, for both types of tunnel junctions the results differ essentially from the well-known ones for the BCS superconductors. There is a qualitative agreement with the scanning tunnelling microscopy measurements for layered dichalcogenides and point-contact spectroscopy measurements for the compound URu2Si2. The explanation of the linear dependence of conductance G on the bias V in the oxide metal junctions is put forward.