Budget Amount *help 
¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1995 : ¥1,400,000 (Direct Cost : ¥1,400,000)

Research Abstract 
Because there exists no intrinsic spinstatistics relation in the planar system, it is possible that electrons condense without making Cooper pairs and that quasiparticles possesses fractional statistics. A concrete example is the fractional quantum Hall (QH) system, which is obtained by applying a strong magnetic field to a planar electron gas. The fractional QH system is most easily understood based on the composteboson picture. Composite bosons are electrons bound to odd units of Dirac flux quanta. Though the compositeboson picture is an excellent way of viewing the system, its fieldtheoretical formulation has so far many unsatisfactory points. We have constructed a selfconsistent field theoretical framework, which allows us to investigate all excitation modes confined within the lowest Landau level (LLL) . Any state in the LLL is described by the wave function omega [z]PSI_<LN> [chi] , where PSI_<LN> [chi] is the Laughlin wave function describing the ground state. Here, omega [z
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] is an analytic function of symmetric N variables. It is the wave function of composite bosons in my theory. Using this scheme, I have analyzed Skyrmion excitations in QF ferromagnets. Our theoretical results account for observed activation energies of Skyrmions quite well. I have also conducted experiments on a bilayr QH system. We have measured the Hallplateau width and the activation energy in the bilayr quantum Hall state at filling factor nu=2,1 and 2/3, by changing the total electron density and the density ratio in the two quantum wells. Their behavior are remarkably different from one to another. The nu=1 state is found stable over all measured range of the density difference, while the nu=2/3 state is stable only around the balanced point. The nu=2 state, on the other hand, shows a phase transition between these two types of the states as the electron density is changed. I have interpreted these experimental facts based on the compositboson picture. In particular, the phase transion in the nu=2 state is understood as the one between the spin ferromagnet and the pseudospin ferromagnet. Less
