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Keshav N. Shrivastava

Publications and source records attributed to Keshav N. Shrivastava.

At least 37 records · Page 2Linked to original sources
arXiv2003

Comments on ``Coexistence of Composite Bosons and Composite Fermions in Quantum Hall Bilayers", Simon et al, cond-mat/0301203

Simon et al suggest that composite fermions (CF) must be replaced by composite bosons (CB) and "111" state is a boson state. However, we find that such a transition in real GaAs is not possible and CF state cannot become a boson. Simon et al suggest that the total number of CF and CB is conserved. However, we find that the number of quasiparticles need not be conserved. Similarly, Simon et al suggest that CFs are formed but we find that this formation does not conserve energy so that CFs will not be formed. Simon et al compute using products of fermion and boson wave functions. We find that the mass of the CF is much too larger than experimental mass. We find that these computed results are not in agreement with the data.

cond-mat.mes-hall↗
arXiv2003

Comments on "Fractional Quantum Hall Effect of Composite Fermions, W. Pan, et al, Phys. Rev. Lett. 90, 016801 (2003)

It is shown that even number of flux quanta are not attached to one electron. The magnetic flux is not detached from the currents and the E and H separation does not occur in the quantum Hall effect, where E is the electric vector and H is the magnetic vector of the electro- magnetic field. We show how a sequence can agree with the experimental data and be wrong also. It is not possible for three electrons to carry 8 flux quanta. There is no temperature in the composite fermion formulas. It may be perfectly acceptable to modify the Biot and Savart's law which is the fundamental law used for making electromagnets but the CFs are internally inconsistent and hence are not suitable as part of fundamentally correct physics.

cond-mat.mes-hall↗
arXiv2002

Fractional charge in quantum Hall effect

In 1976 Jackiw and Rebbi found 1/2 of a fermion number by using Dirac equation in 1+1 dimensions. Schrieffer in several proposals made an effort to suggest that there is a fractional charge. The calculations of Peierls distortion, Berry's phase and classical action were presented to accomodate the fractional charge in non-relativistic theory. Laughlin used the antisymmetry to define the charge density per unit area in a two dimensional system. In order to elliminate the area, Laughlin introduced the incompressibility which fixed the area so that the odd number, which determines the antisymmetry of the electron wave function, gave the charge. We have used the orbital angular momentum and the spin to define the charge, in full agreement with the quantum Hall effect data.

cond-mat.mes-hall↗
arXiv2002

Nonuniqueness of Kivelson, Kallin, Arovas and Schrieffer' fractional charge

It is found that the magnetic length has not been treated correctly to calculate the classical action. In fact, the charge and the magnetic length have not been resolved. It is of serious consequences because fractional charge completely disappears and only the flux area, $ł_o^2$ becomes fractional. The results of Kivelson et al are therefore not unique.

cond-mat.mes-hall↗
arXiv2002

Comments on ``Evidence of Landau Levels and Interactions in Low-Lying Excitations of Composite Fermions ..." by Dujovne, Pinczuk, Kang, Dennis, Pfeiffer and West, cond-mat/0211022

Dujavne et al suggest that the observed spectra are a result of spin-split Landau levels and spin-flip energies reveal composite fermion interactions. We find that the CF effective field formula is incorrect. In fact, CF model is independent of spin so that the interpretations of data by Dujovne et al in terms of CF model are incorrect. It may be pointed out that the experimental mass of the quasiparticles is several orders of magnitude smaller than the CF mass.

cond-mat.mes-hall↗
arXiv2002

Comments on``Theoretical search for the nested quantum Hall effect of composite fermions" by Mandal and Jain,Phys.Rev.B 66,155302(2002); cond-mat/0210181

We find that a large number of parameters are used to create the correct fractions. The parameters used are, ν, 1-ν,ν^*,\bar n, n, p and \bar p. Therefore, the predicted fractions need not be having the correct origin. The wave function describes a composite fermion which has the 2p (even number) of flux quanta attached to one electron. We find that it requires ``decomposite fermion", which is the electron in an orbit from which the magnetic field has been detached. This kind of detachment (attachment) of flux quanta from (to) the electron is not consistent with the electromagnetic theory of light and violates Biot and Savart's law as well as theory of relativity. If flux quanta are to be attached to the electron, we should solve the bound-state equation and determine the binding energy but bound-state has not been solved. The wave function given is not a solution of the bound-state equation. Therefore,Mandal and Jain's composite fermion (CF) model is incorrect. electron, to the electron, we should solve the bound-state equation and determine

cond-mat.mes-hall↗
arXiv2002

The alternative to the incompressible fractional charge in the quantum Hall effect: Comments on Laughlin and Schrieffer's papers

Laughlin has found "exactly" the wave function which is ascribed to an excitation of fractional charge, such as e/3. We find that the exactness of the wave function is not destroyed by changing the charge to some other quantity such as the magnetic field. Thus e/3 and H can be replaced by e and H/3. Therefore, the wave function need not belong to quasiparticles of charge e/3.

cond-mat.mes-hall↗
arXiv2002

Violation of classical electrodynamics by composite fermions in the quantum Hall effect

We find that the composite fermion (CF), which is the magnetic flux quanta attached to the electron, although based on experimentally observed fractions in the quantum Hall effect, is inconsistent with the classical electrodynamics. It produces new quasiparticles which have usual charge and spin but their motion in a curved path does not produce magnetic field. This "zero-field" production is inconsistent with the classical electrodynamics. The attaching and detaching of magnetic flux quanta to the electron also violates the theory of relativity.

cond-mat.mes-hall↗
arXiv2002

The composite fermion model of quantum Hall effect is internally inconsistent

The The composite fermion model (CF) of the quantum Hall effect which gives the correct series of charges is based on attachment of flux quanta to the electron. The construction of the series of charges leads to a field expression which requires that flux quanta are attached to the electron. The series based on the experimental data is correct but the field deduced from such a series is found to be incorrect. The attachment of even number of flux quanta to an electron required by the CF model is found to be internally inconsistent.

cond-mat.mes-hall↗
arXiv2002

2002 Oliver E. Buckley Prize. The discoveries and the priorities

The discovery of the series of minima in the transverse resistivity in the quantum Hall effect as distinguished from the integer quantum Hall effect which gives the value of e^2/h and the fractional value, (1/3)e^2/h, deserves recognition by the American Physical Society. The priorities in performing the experimental work as well as in theoretical understanding of the series of minima in the quantum Hall effect are pointed out.

cond-mat.mes-hall↗
arXiv2002

Composite Fermions Phenomenology in Quantum Hall Effect

An effort is made to understand the phenomenological composite fermion model of the quantum Hall effect. The odd denominators are composed by adding plus minus 1 to the even numbers 2, 4, 6 and 8. Although the denominators are phenomenologically made to agree with the experimental data, the physics of the CF model, i.e., the even flux quanta attachment to the electron is found to be incorrect.

cond-mat.mes-hall↗
arXiv2002

Cyclotron Resonance of Composite Fermions: Quantum Hall Effect

We have examined the claim made by Kukushkin et al that they have observed the cyclotron resonance of composite fermions. We find that the claim made is false and there is no justification for making false reports. The microwave absorption in cyclotron levels is observed and it is claimed that CF has been seen. Since "even flux quanta attachment to one electron" has not been seen, we find that Kukushkin's claim to have seen the CF is false. Since attachment of flux quanta to electrons can be an important discovery, Kukushkin et al have made the claim of seeing the CF without actually identifying them. The data can be interpreted without attaching flux quanta to the electrons.

cond-mat.mes-hall↗
arXiv2002

Multiple gaps in quantum Hall effect including review of prl 1998-2001 papers

The fractions of constant conductivity, i, where the conductivity is ie^2/h are interpretted to arise from the summation of two frequencies, ω_1+ ω_2, type of processes so that the quantum Hall effect becomes a problem of spectroscopic energy levels. We describe the conversion of resistivity to the frequency spectrum. An effort is made to look at the recent articles from the Phys. Rev. Lett. 1998-2001, to see if there are any data which does not agree with our theory. It is found that all of the data agrees with our theory, The papers which claim to provide the theoretical base are found to be irrelevant to the experimental data.

cond-mat.mes-hall↗
arXiv2001

Vortices in Bose-Einstein Condensed Na Atoms

There are surface modes on the Bose-Einstein condensed Na atoms so that the number of vortices diverges when the stirring frequency becomes equal to that of the surface waves. We introduce the finite life time of the surface modes so that the number of vortices becomes finite. Usually the number of vortices is a linear function of the stirring frequency. We find that this linearity is destroyed by the finite life time and a peaked function emerges with several peaks, one for each surface mode. The vortices become normal, as they should be, so that there occurs a phase transition from normal to the superfluid state.

cond-mat.mes-hall↗
arXiv2001

Illumination of quantum Hall effect

We show that illumination by continuous white radiation saturates the population of levels so that some of the transitions are not observed. This reduces the number of observable transitions so that the resolution of transitions is improved. In the case of ν= 11/2 the improved resolution leads to clear observation of zero in the transverse resistivity which appears as a finite resistivity in absence of saturating radiation.

cond-mat.mes-hall↗
arXiv2001

A new phase in the bilayers of semiconductors in quantum Hall effect

We find that a bilayer of semiconductors emits a new Goldstone quasiparticle when Landau levels in the layers are half filled. The emission of the new quasiparticle is associated with the divergence in the energy of the system characteristic of a phase transition. There is a Bose condensation of the pairs of quasiparticles in which one electron has spin up and the other down but the orbital magnetic quantum number is very large so that the spin singlet is very different from the Cooper pairs.

cond-mat.mes-hall↗
arXiv2001

Polarization of the helf-filled Landau level in quantum Hall effect

We develop a theory of the half-filled Landau level which shows that it is a two-component fluid. One of the components has spin up and the other spin down so that the electron-spin resonance can occur. The 1/3 filled level is fully spin polarized one-component fluid. We calculate the spin polarization at the half-filled band as a function of temperature and compare the calculated results with the experimentally measured value. Our theory is in very good agreement with the experimental data of the polarization obtained from the ratio of the Knight shifts.

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