We theoretically investigate the effect of external fields and currents on
electronic nematic orderings based on the concept of augmented multipoles
consisting of electric, magnetic, magnetic toroidal, and electric toroidal
multipoles. We show the relation between rank-2 electric quadrupoles and the
other multipoles, the former of which corresponds to the microscopic order
parameter for the nematic phases. The electric (magnetic) field induces the
rank-1 and rank-3 electric (magnetic) multipoles and rank-2 electric toroidal
(magnetic toroidal) quadrupoles, while the electric current induces the rank-1
and rank-3 magnetic toroidal multipoles and rank-2 magnetic quadrupoles. We
classify the active multipoles under magnetic point groups, which will be a
reference to explore cross-correlation and transport phenomena in nematic
phases.Comment: 7 pages, 1 figure, 7 table