Showing papers on "Landau quantization published in 2000"
TL;DR: The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations and a huge resonant enhancement replaces the strongly suppressed equilibrium tunneling characteristic of weakly coupled layers.
Abstract: The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations. At total Landau level filling νT = 1 the tunnel spectrum changes qualitatively when the boundary separating the compressible phase from the ferromagnetic quantized Hall state is crossed. A huge resonant enhancement replaces the strongly suppressed equilibrium tunneling characteristic of weakly coupled layers. The possible relationship of this enhancement to the Goldstone mode of the broken symmetry ground state is discussed.
359 citations
TL;DR: In this paper, a simple physical model of a particle moving on the infinite non-commutative 2-plane was constructed, which consists of a pair of opposite charges moving in a strong magnetic field.
Abstract: We construct a simple physical model of a particle moving on the infinite noncommutative 2-plane. The model consists of a pair of opposite charges moving in a strong magnetic field. In addition, the charges are connected by a spring. In the limit of large magnetic field, the charges are frozen into the lowest Landau level. Interaction of such particles include Moyal bracket phases characteristics of field theory on noncommutative space. The simple system arises in lightcone quantization of open strings attached to D-branes in a.s. tensor background. We use the model to work out the general form of lightcone vertices from string splitting. We then consider Feynman diagrams in uncompactified NC YM theories and find that for all planar diagrams the comm. and noncomm. theories are the same. This means large N theories are equivalent in the 't Hooft limit. Non planar diagrams convergence is improved.
355 citations
TL;DR: In this article, the effects of very strong magnetic fields on the equation of state (EOS) in multicomponent, interacting matter by developing a covariant description for the inclusion of the anomalous magnetic moments of nucleons was studied.
Abstract: We study the effects of very strong magnetic fields on the equation of state (EOS) in multicomponent, interacting matter by developing a covariant description for the inclusion of the anomalous magnetic moments of nucleons For the description of neutron star matter, we employ a field-theoretical approach, which permits the study of several models that differ in their behavior at high density Effects of Landau quantization in ultrastrong magnetic fields (B > 1014 G) lead to a reduction in the electron chemical potential and a substantial increase in the proton fraction We find the generic result for B > 1018 G that the softening of the EOS caused by Landau quantization is overwhelmed by stiffening due to the incorporation of the anomalous magnetic moments of the nucleons In addition, the neutrons become completely spin polarized The inclusion of ultrastrong magnetic fields leads to a dramatic increase in the proton fraction, with consequences for the direct Urca process and neutron star cooling The magnetization of the matter never appears to become very large, as the value of |H/B| never deviates from unity by more than a few percent Our findings have implications for the structure of neutron stars in the presence of large frozen-in magnetic fields
310 citations
TL;DR: In this paper, a self-interacting two-level system depending on an external parameter is investigated and the most striking feature exhibited in this system is the presence of a nonzero tunneling probability in the adiabatic limit for large enough interaction strength.
Abstract: A self-interacting two-level system depending on an external parameter is investigated. The most striking feature exhibited in this system is the presence of a nonzero tunneling probability in the adiabatic limit for large enough interaction strength. Possible experimental observation of this breakdown of adiabaticity using a Bose-Einstein condensate in an optical potential is suggested.
280 citations
TL;DR: In the higher Landau level (nu = 5/2), a first-order phase transition separating a compressible striped phase from a paired quantum Hall state, which is identified as the Moore-Read state.
Abstract: We consider the two lowest Landau levels at half filling. In the higher Landau level $(\ensuremath{
u}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5/2)$, we find a first-order phase transition separating a compressible striped phase from a paired quantum Hall state, which is identified as the Moore-Read state. The critical point is very near the Coulomb potential and the transition can be driven by increasing the width of the electron layer. We find a much weaker transition (either second-order or a crossover) from pairing to the composite fermion Fermi-liquid behavior. A very similar picture is obtained for the lowest Landau level, but the transition point is not near the Coulomb potential.
241 citations
TL;DR: In this article, the influence of topological defects on the spectrum of the electron in a magnetic field in the framework of the geometric theory of defects in solids of Katanaev and Volovich is studied.
Abstract: We study the Landau levels associated with electrons moving in a magnetic field in the presence of a continuous distribution of disclinations, a magnetic screw dislocation and a dispiration. We focus on the influence of these topological defects on the spectrum of the electron(or hole) in a magnetic field in the framework of the geometric theory of defects in solids of Katanaev and Volovich. The presence of the defects breaks the degeneracy of the Landau levels in different ways depending on the defect. Exact expressions for energies and eigenfuctions are found for all cases.
111 citations
TL;DR: A scanning probe technique was used to obtain a high-resolution map of the random electrostatic potential inside the quantum Hall liquid, and a sharp metal tip sensed charges in an embedded two-dimensional (2D) electron gas.
Abstract: A scanning probe technique was used to obtain a high-resolution map of the random electrostatic potential inside the quantum Hall liquid. A sharp metal tip, scanned above a semiconductor surface, sensed charges in an embedded two-dimensional (2D) electron gas. Under quantum Hall effect conditions, applying a positive voltage to the tip locally enhanced the 2D electron density and created a "bubble" of electrons in an otherwise unoccupied Landau level. As the tip scanned along the sample surface, the bubble followed underneath. The tip sensed the motions of single electrons entering or leaving the bubble in response to changes in the local 2D electrostatic potential.
105 citations
TL;DR: In this paper, the Hartree-Fock theory was used for the dependence of the sign and magnitude of the pseudospin anisotropy energy on the nature of the crossing Landau levels.
Abstract: Broken-symmetry ground states with uniform electron density are common in quantum Hall systems when two Landau levels simultaneously approach the chemical potential at integer filling factor $\ensuremath{
u}.$ The close analogy between these two-dimensional electron system states and conventional itinerant electron ferromagnets can be emphasized by using a pseudospin label to distinguish the two Landau levels. As in conventional ferromagnets, the evolution of the system's state as external field parameters are varied is expected to be sensitive to the dependence of ground-state energy on pseudospin orientation. We discuss the predictions of Hartree-Fock theory for the dependence of the sign and magnitude of the pseudospin anisotropy energy on the nature of the crossing Landau levels. We build up a classification scheme for quantum Hall ferromagnets that applies for single layer and bilayer systems with two aligned Landau levels distinguished by any combination of real spin, orbit radius, or growth direction degree-of-freedom quantum numbers. The possibility of in situ tuning between easy-axis and easy-plane quantum Hall ferromagnets is discussed for biased bilayer systems with total filling factors $\ensuremath{
u}=3$ or $\ensuremath{
u}=4.$ Detailed predictions are made for the bias dependence of pseudospin reversal properties in $\ensuremath{
u}=3$ bilayer systems.
95 citations
TL;DR: A novel singular gauge transformation is developed for quasiparticles in the mixed state of a strongly type-II superconductor which permits a full solution of the problem at low and intermediate fields, H(c1)
Abstract: A novel singular gauge transformation is developed for quasiparticles in the mixed state of a strongly type-II superconductor which permits a full solution of the problem at low and intermediate fields, H(c1)
91 citations
TL;DR: In this article, the weak field expansion of the charged fermion propagator under a uniform magnetic field was studied and the leading and sub-leading magnetic field effects to the above processes were computed.
Abstract: The weak-field expansion of the charged fermion propagator under a uniform magnetic field is studied. Starting from Schwinger's proper-time representation, we express the charged fermion propagator as an infinite series corresponding to different Landau levels. This infinite series is then reorganized according to the powers of the external field strength B. For illustration, we apply this expansion to $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}\ensuremath{
u}\overline{\ensuremath{
u}}$ and $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{
u}}\ensuremath{
u}\ensuremath{\gamma}$ decays, which involve charged fermions in the internal loop. The leading and subleading magnetic-field effects to the above processes are computed.
90 citations
TL;DR: In this article, the authors discussed the breakdown of the integer quantum Hall effect (IQHE) based on the consideration of heat stability of a two-dimensional electron gas (2DEG).
Abstract: Breakdown of the integer quantum Hall effect (IQHE) is discussed based on the consideration of heat stability of a two-dimensional electron gas (2DEG). First, the 2DEG system in the IQHE state is suggested to become thermally unstable when the Hall electric field ${E}_{y}$ reaches a threshold value ${E}_{b}.$ Above ${E}_{b},$ a small number of excited electrons in the higher Landau level, which are initially present in the conductor as fluctuation, are accelerated by ${E}_{y},$ and the 2DEG thereby undergoes a transition to a warm dissipative state. This abrupt transition is referred to as the bootstrap-type electron heating (BSEH). Second, the critical field, ${E}_{b},$ for BSEH is theoretically derived and compared with the experimental values of the IQHE breakdown reported earlier by different groups. The agreement is satisfactory, suggesting that BSEH is the basic mechanism behind the IQHE breakdown. Third, dynamical aspects of BSEH are discussed. It is argued that the BSEH is a process of the avalanche-type electron-hole pair multiplication, in which a small number of nonequilibrium carriers gains kinetic energy within a Landau level and excites other electron-hole pairs via the inter-Landau-level impact ionization. Electrons travel a macroscopic distance during the process of electron-hole multiplication. This feature is confirmed by experiments. Experiments indicate that ${E}_{y}$ does not locally influence the longitudinal conductivity when the IQHE breaks down, providing definite proof of BSEH. Finally, a variety of characteristics of the IQHE, reported in earlier works, is reviewed and suggested to be consistent with the BSEH model.
TL;DR: In this paper, the Mourre theory of positive commutators is applied to prove absolute continuity of the energy spectrum well in between Landau levels, corresponding to edge states, for a two-dimensional electron gas confined to a half-plane, or to a domain in the plane satisfying a certain geometric condition.
Abstract: Properties of eigenstates of one-particle Quantum Hall Hamiltonians localized near the boundary of a two-dimensional electron gas – so-called edge states – are studied. For finite samples it is shown that edge states with energy in an appropriate range between Landau levels remain extended along the boundary in the presence of a small amount of disorder, in the sense that they carry a non-zero chiral edge current. For a two-dimensional electron gas confined to a half-plane, or to a domain in the plane satisfying a certain geometric condition, the Mourre theory of positive commutators is applied to prove absolute continuity of the energy spectrum well in between Landau levels, corresponding to edge states.
TL;DR: The repulsive Coulomb interaction between electrons is overscreened in the ν = 5/2 state by the formation of composite fermions, resulting in a weak, attractive interaction.
Abstract: When confined to two dimensions and exposed to a strong magnetic field, electrons screen the Coulomb interaction in a topological fashion; they capture an even number of quantum vortices and transform into particles called 'composite fermions' (refs 1-3). The fractional quantum Hall effect occurs in such a system when the ratio (or 'filling factor, nu) of the number of electrons and the degeneracy of their spin-split energy states (the Landau levels) takes on particular values. The Landau level filling nu = 1/2 corresponds to a metallic state in which the composite fermions form a gapless Fermi sea. But for nu = 5/2, a fractional quantum Hall effect is observed instead; this unexpected result is the subject of considerable debate and controversy. Here we investigate the difference between these states by considering the theoretical problem of two composite fermions on top of a fully polarized Fermi sea of composite fermions. We find that they undergo Cooper pairing to form a p-wave bound state at nu = 5/2, but not at nu = 1/2. In effect, the repulsive Coulomb interaction between electrons is overscreened in the nu = 5/2 state by the formation of composite fermions, resulting in a weak, attractive interaction.
TL;DR: In this paper, the long-time evolution of nonlinear Landau damping in collisionless plasmas is analyzed by solving the Vlasov-Poisson system numerically, and the value of the parameter marking the transition between Landau's and O'Neil's regimes is determined and compared with analytical results.
Abstract: The long-time evolution of nonlinear Landau damping in collisionless plasmas is analyzed by solving the Vlasov-Poisson system numerically. The value of the parameter marking the transition between Landau's and O'Neil's regimes is determined and compared with analytical results. The long-time evolution of a finite-amplitude electric field with wavelength $\ensuremath{\lambda}$ equal to the length of the simulation box L is given by a superposition of two counterpropagating ``averaged'' Bernstein-Greene-Kruskal (BGK) waves. When $Lg\ensuremath{\lambda}$ and longer wavelength modes can be excited, the BGK waves correspond to an intermediate regime that is eventually modified by the excitation of the sideband instability. Ions dynamics is found not to affect these behaviors significantly.
TL;DR: In this article, the authors investigated the Hallpotential profiles of a two-dimensional electron system (2DES) under quantum Hall (QH) conditions at T=1.4 K with submicron resolution using a scanning force microscope sensitive to electrostatics.
Abstract: Hall-potential profiles of a two-dimensional electron system (2DES) under quantum Hall (QH) conditions have been investigated at T=1.4 K with submicron resolution using a scanning force microscope sensitive to electrostatics. At an even integer Landau level filling factor a rather nonlinear Hall-potential profile across the Hall-bar is observed. But at reduced magnetic field values corresponding to filling factors slightly above this even integer value almost no Hall-potential drop across the bulk region is found. Instead, the potential clearly drops across prominent areas associated with the positions of incompressible strips that just had emerged at that filling factor at both edges. This shows that the dominant incompressible strips of locally even integer filling factor can decouple the bulk from the edge, thus demonstrating the importance of the edge region for the Hall-field distribution even at non-integer filling factors.
TL;DR: In this article, an enhancement of terahertz intersubband electroluminescence in a quantum cascade structure was observed in the presence of a magnetic field applied normal to the epitaxial layers.
Abstract: We have observed an enhancement of terahertz intersubband electroluminescence in a quantum cascade structure in the presence of a magnetic field applied normal to the epitaxial layers. At a field of B=7.2 T the emission efficiency doubles. This effect is attributed to the suppression of nonradiative Auger–intersubband transitions caused by Landau-quantization of the in-plane electron motion. The magnetic field dependence of the luminescence intensity shows strong oscillations. These magnetointersubband oscillations are caused by the modulation of the transition rate via resonant inter-Landau-level transfer.
TL;DR: Using a "standard" NMR spin-echo technique, the spin polarization P of two-dimensional electrons, confined to GaAs quantum wells, is determined from the hyperfine shift of Ga nuclei located in the wells, by a simple model of noninteracting composite fermions.
Abstract: Using a "standard" NMR spin-echo technique we determined the spin polarization P of two-dimensional electrons, confined to GaAs quantum wells, from the hyperfine shift of Ga nuclei located in the wells. Concentrating on the temperature ( 0.05 less, similarT less, similar10 K) and magnetic field ( 7 less, similarB less, similar17 T) dependencies of P at Landau level filling factor nu = 1/2, we find that the results are described well by a simple model of noninteracting composite fermions, although some inconsistencies remain when the two-dimensional electron system is tilted in the magnetic field.
TL;DR: It is shown that recent experiments, claiming to observe a discrepancy with the global phase diagram of the quantum Hall effect, are in fact in agreement with the standard theory.
Abstract: The temperature and scale dependence of resistivities in the standard scaling theory of the integer quantum Hall effect is discussed. It is shown that recent experiments, claiming to observe a discrepancy with the global phase diagram of the quantum Hall effect, are in fact in agreement with the standard theory. The apparent low-field transition observed in the experiments is identified as a crossover due to weak localization and a strong reduction of the conductivity when Landau quantization becomes dominant.
TL;DR: The results are strongly suggestive of a breakdown of translational symmetry and the presence of crystalline order in the ground state in two-dimensional electron gas systems subject to a perpendicular magnetic field, with a high Landau level partially filled by electrons.
Abstract: We report on results of systematic numerical studies of two-dimensional electron gas systems subject to a perpendicular magnetic field, with a high Landau level partially filled by electrons. Our results are strongly suggestive of a breakdown of translational symmetry and the presence of crystalline order in the ground state. This is in sharp contrast with the physics of the lowest and first excited Landau levels, and in good qualitative agreement with earlier Hartree-Fock studies. Experimental implications of our results are discussed.
TL;DR: A single InAs self-assembled quantum dot is incorporated in the barrier of a tunnel diode and used as a spectroscopic probe of an adjacent two-dimensional electron system from the Fermi energy to the subband edge to obtain quantitative information about the energy dependence of the quasiparticle lifetime.
Abstract: A single InAs self-assembled quantum dot is incorporated in the barrier of a tunnel diode and used as a spectroscopic probe of an adjacent two-dimensional electron system from the Fermi energy to the subband edge. We obtain quantitative information about the energy dependence of the quasiparticle lifetime. For magnetic field $B$, applied parallel to the current, we observe peaks in the current-voltage characteristics $I(V)$ corresponding to the formation of Landau levels. Close to filling factor $\ensuremath{
u}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ we observe directly the exchange enhancement of the Land\'e $g$ factor.
TL;DR: Simulations support predictions providing new insight into the long-time nonlinear fate of the wave due to Landau damping in plasmas, and a critical initial wave intensity is found.
Abstract: Gibbs statistical mechanics is derived for the Hamiltonian system coupling a wave to $N$ particles self-consistently. This identifies Landau damping with a regime where a second order phase transition occurs. For nonequilibrium initial data with warm particles, a critical initial wave intensity is found: above it, thermodynamics predicts a finite wave amplitude in the limit $N\ensuremath{\rightarrow}\ensuremath{\infty}$; below it, the equilibrium amplitude vanishes. Simulations support these predictions providing new insight into the long-time nonlinear fate of the wave due to Landau damping in plasmas.
Abstract: Asymmetrically modulation-doped HgTe quantum wells of (0 0 1) orientation were produced by molecular beam epitaxy. N-type doping was achieved with iodine and p-type doping by the incorporation of nitrogen. At 4.2 K the n-type samples have electron mobilities up to 10 5 cm 2 / Vs , the maximum Hall mobility of the p-type specimens is around 2×10 4 cm 2 / Vs . Very pronounced Shubnikov–de Haas oscillations were observed in both n-type and p-type samples. In the n-type specimens the quantum oscillations persisted up to temperatures of 60 K. The Shubnikov–de Haas oscillations in the p-type samples were highly irregular. Because the data cannot be explained without detailed theoretical calculations of Landau levels for the heterostructure self consistent Hartree calculations were performed using a 8×8 k · p model. The magnetic field-dependent density of states was calculated. More regular oscillations are predicted at higher magnetic fields approaching 30 T.
TL;DR: It is found that a transition from perpendicular to parallel stripes exists when the electron gas thickness exceeds approximately 60 A, and the perpendicular alignment of the stripes is in agreement with the experimental finding that the easy conduction direction is perpendicular to the in-plane field.
Abstract: We study here the onset of charge density wave instabilities in quantum Hall systems at finite temperature for Landau level filling nu>4. Specific emphasis is placed on the role of disorder as well as on an in-plane magnetic field. Beyond some critical value, disorder is observed to suppress the charge density wave melting temperature to zero. In addition, we find that a transition from perpendicular to parallel stripes (relative to the in-plane magnetic field) exists when the electron gas thickness exceeds approximately 60 A. The perpendicular alignment of the stripes is in agreement with the experimental finding that the easy conduction direction is perpendicular to the in-plane field.
01 Mar 2000
TL;DR: In this paper, the onset of charge density wave instabilities in quantum Hall systems at finite temperature for Landau level filling nu>4 was studied and the role of disorder as well as on an in-plane magnetic field.
Abstract: We study here the onset of charge density wave instabilities in quantum Hall systems at finite temperature for Landau level filling nu>4. Specific emphasis is placed on the role of disorder as well as on an in-plane magnetic field. Beyond some critical value, disorder is observed to suppress the charge density wave melting temperature to zero. In addition, we find that a transition from perpendicular to parallel stripes (relative to the in-plane magnetic field) exists when the electron gas thickness exceeds approximately 60 A. The perpendicular alignment of the stripes is in agreement with the experimental finding that the easy conduction direction is perpendicular to the in-plane field.
TL;DR: Magnetoresistance data taken along [ 2 3 3] and [ 0 1 1 ] directions in a GaAs/AlGaAs two-dimensional hole sample with van der Pauw geometry exhibit significant anisotropy at half-integer filling factors as discussed by the authors.
Abstract: Magnetoresistance data taken along [ 2 3 3] and [0 1 1 ] directions in a GaAs/AlGaAs two-dimensional hole sample with van der Pauw geometry exhibit significant anisotropy at half-integer filling factors. The anisotropy appears to depend on both the density and symmetry of the hole charge distribution.
TL;DR: In this article, the authors considered a layered superconductor in a magnetic field of arbitrary orientation with respect to the conducting plane and found new order parameter structures differing from both the traditional Abrikosov and FFLO solutions.
Abstract: Clean superconductors with weakly coupled conducting planes have been suggested as promising candidates for observing the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state. We consider here a layered superconductor in a magnetic field of arbitrary orientation with respect to the conducting plane. In this case there is competition of Pauli spin-pair-breaking effects, favoring the FFLO state, and orbital-pair-breaking effects, favoring the Abrikosov vortex state. In previous work, phase transitions to phases with pairing in Landau levels with quantum numbers n > 0 have been predicted. Here, we calculate the actual structure of the stable states below H
c2 by minimizing the free energy. We find new order parameter structures differing from both the traditional Abrikosov and FFLO solutions. These include two-dimensional periodic structures with several zeros of the order parameter, as well as quasi-one-dimensional structures consisting of vortex chains separated by FFLO domains. We discuss the limit of high n, where some interesting but yet unsolved questions appear.
TL;DR: Taut et al. as mentioned in this paper showed that the Schrodinger equation for three electrons in a homogeneous magnetic field and a parabolic scalar confinement potential (frequency ω0) has analytical solutions in the limit where the expectation value of the centre-of-mass vector R is small compared with the average distance between the electrons.
Abstract: We found that the two-dimensional Schrodinger equation for three electrons in a homogeneous magnetic field (perpendicular to the plane) and a parabolic scalar confinement potential (frequency ω0) has analytical solutions in the limit where the expectation value of the centre-of-mass vector R is small compared with the average distance between the electrons. These analytical solutions exist only for certain discrete values of the effective frequency . Furthermore, for finite external fields, the total angular momenta must be ML = 3m with m = integer, and spins have to be parallel. The analytically solvable states are always cusp states, and take the components of higher Landau levels into account. These special analytical solutions for three particles and the exact solutions for two particles (Taut M 1994 J. Phys. A: Math. Gen. 27 1045 and Taut M 1994 J. Phys. A: Math. Gen. 27 4723 (erratum)) can be written in a unified form. The first set of solutions reads where the pn,m(x) are certain finite polynomials and n ,m is the spectrum of the fields. The pair angular momentum m has to be an odd integer and the integer n defines the number of terms in the polynomials. For infinite solvable fields 1 , there is a second set of the form where Aa is the antisymmetrizer and the pair angular momentum mik can all be different integers. In both cases the first factor is a short-hand form with the convention r m = r |m | eim . These formulae, when ad hoc generalized to N coordinates, can be discussed as an ansatz for the wave function of the N -particle system. This ansatz fulfils the following requirements: it is exact for two particles and for three particles in the limit of small R and for the solvable external fields, and it is an eigenfunction of the total orbital angular momentum. The Laughlin functions are special cases of this ansatz for infinite solvable fields and equal pair angular momenta.
TL;DR: In this article, the authors describe the quantum Hall effect on a two-dimensional electron gas at low temperatures and show that when the magnetic field is decreased at fixed carrier density n, the localized and extended states move down in energy and alternately pass through the Fermi energy.
Abstract: In a perpendicular magnetic field a two-dimensional electron gas ~2DEG! at low temperatures exhibits the quantum Hall ~QH! effect. In a strong magnetic field there are Landau levels ~LL’s !, and the picture of extended states at the LL centers and localized states between LL’s provides a simple description of the quantum Hall effect. When the magnetic field~B! is decreased at fixed carrier density n, the localized and extended states move down in energy and alternately pass through the Fermi energy. When the Fermi energy passes through the extended states, both r xx and r xy vary smoothly. In contrast, when the Fermi energy is between LL’s and pinned in the localized states, the transverse resistivity r xy is quantized, and the longitudinal resistivity r xx !0 as the temperature is reduced to zero.
TL;DR: In this article, the Coulomb pseudopotential V(L) (pair energy as a function of pair angular momentum) in the lowest Landau level (LL) is defined that leads to short-range Laughlin-like correlations in many-body systems and to which the CF model can be applied.
Abstract: The mean-field composite fermion (CF) picture successfully predicts angular momenta of multiplets forming the lowest-energy band in fractional auantum Hall (FQH) systems. This success cannot be attributed to a cancellation between Coulomb and Chern-Simons interactions beyond the mean field, because these interactions have totally different energy scales. Rather, it results from the behaviour of the Coulomb pseudopotential V(L) (pair energy as a function of pair angular momentum) in the lowest Landau level (LL). The class of short-range repulsive pseudopotentials is defined that lead to short-range Laughlin-like correlations in many-body systems and to which the CF model can be applied. These Laughlin correlations are described quantitatively using the formalism of fractional parentage. The discussion is illustrated with an analysis of the energy spectra obtained in numerical diagonalization of up to 11 electrons in the lowest and excited LLs. The qualitative difference in the behaviour of V(L)is ...