Quantum Kinetic Theory of Collisionless Superfluid Internal Convection

Superfluids can transport heat via simultaneous opposite flows of their spatially interpenetrating condensate and noncondensate components. While this internal convection is usually described within Landau’s phenomenological two-fluid hydrodynamics, we apply quantum kinetic theory to a dilute Bose gas held between thermal reservoirs at different temperatures and show that the phenomenon also appears in collisionless kinetic regimes and should be directly observable in currently feasible experiments on trapped ultracold vapors.

Figure 1

Internal convection: a condensed Bose gas in contact with heat baths of different temperatures $T_L>T_R$. Condensate flows towards the hotter reservoir, noncondensate in the opposite direction.