The energy spectra and wavefunctions of up to 14 interacting quasielectrons (QE's) in the Laughlin ν = 1 3 fractional quantum Hall (FQH) state are investigated using exact numerical diagonalization. It is shown that at sufficiently high density the QE's form pairs or larger clusters. This behavior, opposite to Laughlin correlations, invalidates the (sometimes invoked) reapplication of the composite fermion picture to the individual QE's. The series of finite-size incompressible ground states are identified at the QE filling factors νQE = 1 2 , 1 3 , 2 3 , corresponding to the electron fillings ν = 3 8 , 4 11 , 5 13 . The equivalent quasihole (QH) states occur at νQH = 1 4 , 1 5 , 2 7 , corresponding to ν = 3 10 , 4 13 , 5 17 . All these six novel FQH states were recently discovered experimentally. Detailed analysis indicates that QE or QH correlations in these states are different from those of well-known FQH electron states (e.g., Laughlin or Moore-Read states), leaving the origin of their incompressibility uncertain. Halperin's idea of Laughlin states of QP pairs is also explored, but is does not seem adequate.

Electron-hole systems on a Haldane sphere are studied by exact numerical diagonalization. Low lying states contain one or more types of bound charged excitonic complexes X − k , interacting through appropriate pseudopotentials. Incompressible ground states of such multi-component plasmas are found. A generalized multi-component Laughlin wavefunction and composite Fermion picture are shown to predict the low lying states of an electron-hole gas at any value of the magnetic field.71.10. Pm, 73.20.Dx, 73.40.Hm, 71.35.Ji Introduction. Recently there has been considerable interest in two dimensional systems containing both electrons and holes in the presence of a strong magnetic field. 1-8 In such systems, neutral (X 0 ) and charged excitons (X − ) and larger exciton complexes (X − k , k neutral X 0 's bound to an electron) can occur. The excitonic ions X − k are long-lived Fermions, 6,7 whose energy spectra contain Landau level structure. 4,7 In this paper we investigate by exact numerical diagonalization small systems containing N e electrons and N h holes (N e ≥ N h ), confined to the surface of a Haldane sphere. 9 For N h = 1 these systems serve as simple guides to understanding photoluminescence. [1][2][3][4][5] For larger values of N h it is possible to form a multi-component plasma containing electrons and X − k complexes. 7 We propose a model 10 for determining the incompressible quantum fluid states 11 of such plasmas, and confirm the validity of the model by numerical calculations. In addition, we introduce a new generalized composite Fermion (CF) picture 12 for the multi-component plasma and use it to predict the low lying bands of angular momentum multiplets for any value of the magnetic field.Bound States. In a sufficiently strong magnetic field, the only bound electron-hole complexes are the neutral exciton X 0 and the spin-polarized charged excitonic ionsAll other complexes found at weaker magnetic fields (e.g. spin-singlet charged exciton 1 or spin-singlet biexciton) unbind. 8 The angular momenta of complexes X 0 and X − k on a Haldane sphere 9 with monopole strength 2S are l X 0 = 0 and l X − k = |S| − k. 7 The binding energies of an exciton, ε 0 = −E X 0 , and of excitonic ions, ε k = E X − k−1 + E X 0 − E X −

An ambipolar dual-channel field-effect transistor (FET) with a WSe /MoS heterostructure formed by separately controlled individual channel layers is demonstrated. The FET shows a switchable ambipolar behavior with independent carrier transport of electrons and holes in the individual layers of MoS and WSe , respectively. Moreover, the photoresponse is studied at the heterointerface of the WSe /MoS dual-channel FET.