Electromotive power generated by pressure gradient in metals with the band Jahn-Teller effect

Abstract

In band Jahn-Teller (BJT) metals, some lattice distortions with their symmetries different from that of the bulk structure can linearly couple to the BJT electrons, so pressures to produce or enhance such distortions can affect the BJT electrons near the Fermi level. This pressure-electric effect in BJT metals is studied theoretically on the basis of the ${\mathrm{\ensuremath{\Gamma}}}_{12}$ subband model for the structural transition in A15 compounds. The applied pressure is assumed to consist of a spatially uniform pressure and a local pressure. The former induces or enhances a uniform distortion, which contributes to the redistribution of electrons between the ${\mathrm{\ensuremath{\Gamma}}}_{12}$ subbands, while the latter produces a local distortion with its gradient, which causes flows of band electrons between different regions in space. The steady electronic state under the uniform and local pressures is obtained by use of the Boltzmann equation and the relaxation-time approximation. It is clarified that the local pressure with its gradient can generate an electromotive power when the degeneracy of the BJT subbands is lifted spontaneously and/or by the external uniform pressure. The obtained pressure-gradient electric effect is predicted to be a probe into BJT effects which may work in some metals with structural transitions.