Excitonic ions and pseudopotentials in two-dimensional systems: Evidence for quantum Hall states of an X- gas

Systems of up to 12 electrons and six holes on the Haldane sphere are studi ed by exact numerical diagonalization. The low-lying states of the system i nvolve bound excitonic complexes such as X-n(-). The angular momenta of the se complexes and the pseudopotentials describing their interaction are dete rmined. The similarity to the electron pseudopotential suggests the possibi lity of incompressible ground states of a gas of X- ions for nu less than o r equal to 1/3. The nu=1/3 states of three and four X-'s are found. [S0163- 1829(99)07639-0].