Nondissipative-Drag Effect in Double-Layer Fractional Quantum Hall Systems

I show that a double-layer fractional quantum Hall state ( kkk ) with filling fraction 1/ k possesses a nondissipative-drag effect, namely, a Hall voltage/current applied to one layer induces a dragged Hall voltage/current in the second layer. This effect is a subtle consequence of a recently discovered neutral gapless mode with linear dispersion (Wen X. G. and Zee A., Phys. Rev. Lett. , 69 (1992) 1811), and it should be observable experimentally.