Fractional quantum Hall fluid with even denominator filling factor and Berry phase

It is shown that the characteristic features of a fractional quantum Hall (FQH) fluid with even denominator filling factor can be well understood from the viewpoint that the Berry phase in this case can be removed to the dynamical phase. However, we can observe the Berry phase when the state is split into pairs of degenerate fermions giving rise to the non-Abelian Berry phase, which suggests that these FQH states correspond to a non-Abelian Hall fluid. From this analysis, it is observed that FQH fluids with filling factors having odd and even denominator can be studied in a unified way. (C) 1997 Published by Elsevier Science B.V.