180 research outputs found
Novel Families of Fractional Quantum Hall States: Pairing of Composite Fermions
Fractional quantum Hall (FQH) states have recently been observed at
unexpected values of the filling factor nu. Here we interpret these states as a
novel family of FQH states involving pairing correlations rather than Laughlin
correlations among the quasiparticles (QP's). The correlations depend upon the
behavior of the QP-QP pseudopotential V_QP(L'), the interaction energy of a
pair as a function of the pair angular momentum L'. This behavior, known from
numerical studies of small systems, is used to demonstrate that pairing
correlations give rise to FQH states at the experimentally observed values of
nu.Comment: to appear in Physics Letters
Residual interactions and correlations among Laughlin quasiparticles: Novel hierarchy states
The residual interactions between Laughlin quasiparticles can be obtained
from exact numerical diagonalization studies of small systems. The
pseudopotentials V_QP(R)$ describing the energy of interaction of QE's (or
QH's) as a function of their "relative angular momentum" R cannot support
Laughlin correlations at certain QP filling factors (e.g., nu_QE}=1/3 and
nu_QH=1/5). Because of this the novel condensed quantum fluid states observed
at nu=4/11, 4/13 and other filling fractions cannot possibly be spin polarized
Laughlin correlated QP states of the composite Fermion hierarchy. Pairing of
the QP's clearly must occur, but the exact nature of the incompressible ground
states is not completely clear.Comment: 5 pages, 2 figures, accepted for Solid State Commu
Hund's Rule for Monopole Harmonics, or Why the Composite Fermion Picture Works
The success of the mean field composite Fermion (MFCF) picture in predicting
the lowest energy band of angular momentum multiplets in fractional quantum
Hall systems cannot be found in a cancellation between the Coulomb and
Chern--Simons interactions beyond the mean field, due to their totally
different energy scales. We show that the MFCF approximation can be regarded as
a kind of semi-empirical Hund's rule for monopole harmonics. The plausibility
of the rule is easily established, but rigorous proof relies on comparison with
detailed numerical calculations.Comment: RevTeX + 3 EPS figures formatted in the text with epsf.st
Composite Fermions and the Fractional Quantum Hall Effect
The mean field (MF) composite Fermion (CF) picture successfully predicts low
lying states of fractional quantum Hall systems. This success cannot be
attributed to a cancellation between Coulomb and Chern-Simons interactions
beyond the mean field and solely depends on the short range (SR) of the Coulomb
pseudopotential in the lowest Landau level (LL). The class of pseudopotentials
for which the MFCF picture can be applied is defined. The success or failure of
the MFCF picture in various systems (electrons in excited LL's, Laughlin
quasiparticles, charged magneto-excitons) is explained.Comment: 10 pages + 4 figures (RevTeX+epsf.sty); submitted to Acta Phys. Pol.
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