Hydrodynamics with triangular point group

When continuous rotational invariance of a two-dimensional fluid is broken to the dis-crete, dihedral subgroup D6 - 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 D6-symmetric fluids, identifying new symmetry-allowed dissipative terms in the hydro-dynamic equations of motion. We propose two experiments - both involving high-purity solid-state materials with D6-invariant Fermi surfaces - that are sensitive to these new coefficients in a D6-invariant electron fluid. In particular, we propose a local current imaging experiment (which is present-day realizable with nitrogen vacancy center mag-netometry) in a hexagonal device, whose D6-exploiting boundary conditions enable the unambiguous detection of these novel transport coefficients.