(257c) Odd Viscodiffusive Chiral Fluids

We present a class of materials termed "viscodiffusive fluids," which exhibit odd cross-couplings between viscous and diffusive transport. The oddity emerges from generating fluxes orthogonal to driving forces—that is, when diffusive fluxes arise due to a velocity gradient, or, reciprocally, when antisymmetric shearing stresses arise under a concentration gradient. By analyzing microscopic fluctuations in the steady state, we use the recently proposed “flux hypothesis” to develop Green-Kubo and reciprocal relations for the governing transport coefficients. These relations suggest that only parity symmetry, and not time-reversal symmetry, must be broken at the microscopic scale to observe odd transport via viscodiffusive couplings. We discuss a few analytically tractable boundary value problems that demonstrate the nature of viscodiffusive cross-coupling, and end with testing the theory on recent experiments on the diffusion of immotile chiral bacteria in response to Poiseuille flows.