Hydrodynamics with triangular point group

Abstract

When continuous rotational invariance of a two-dimensional fluid is broken to the discrete, dihedral subgroup D_6D6 - the point group of an equilateral triangle - the resulting anisotropic hydrodynamics breaks both spatial-inversion and time-reversal symmetries, while preserving their combination. In this work, we present the hydrodynamics of such D_6D6-symmetric fluids, identifying new symmetry-allowed dissipative terms in the hydrodynamic equations of motion. We propose two experiments - both involving high-purity solid-state materials with D_6D6-invariant Fermi surfaces - that are sensitive to these new coefficients in a D_6D6-invariant electron fluid. In particular, we propose a local current imaging experiment (which is present-day realizable with nitrogen vacancy center magnetometry) in a hexagonal device, whose D_6D6-exploiting boundary conditions enable the unambiguous detection of these novel transport coefficients.