Thermodynamic Multipoles and Dissipative Conductivities in Metallic Systems

Abstract

Multipoles provide a systematic framework for describing the electronic structures of quantum materials from a symmetry perspective. Thermodynamic multipole moments in crystalline solids exhibit direct microscopic connections to certain allowed physical responses beyond symmetry; however, such relations have thus far been limited to dissipationless responses in equilibrium insulating systems. Here, this framework is extended at a heuristic level by focusing on the Fermi-surface contributions to thermodynamic multipole moments. These contributions establish direct relations to dissipative transport responses characteristic of metals, including charge and spin conductivities. A key consequence is that the conductivities exhibit extrema, typically maxima, at chemical potentials where the corresponding Fermi-surface contributions to the multipoles vanish, specifically, the electric quadrupole for charge conductivity and the magnetic octupole for spin conductivity. These findings uncover a previously overlooked aspect of thermodynamic multipole moments, opening a new perspective on dissipative transport in metallic systems.

Figures (1)

• Figure 1: Chemical-potential dependence of the Fermi-surface contribution (black), total thermodynamic multipole (red), and the corresponding dissipative conductivity tensor (blue) are shown. The thermodynamic multipole and the conductivity are plotted in arbitrary units. Note that their horizontal scales are different.