  We study the triangular $t$-$J$ model with multiple spin exchange
interactions using exact diagonalization of small clusters, as a model of
monolayer liquid $^3$He. A phase where the energy spectrum suggest the
behaviors of spin-charge separation is realized in the doped-Mott region due to
the competition between ferromagnetic two-spin and antiferromagnetic four-spin
exchange interactions. This behavior gives an interpretation of the double
peaked heat capacity recently observed in monolayer liquid $^3$He adsorbed on a
graphite.
