3,107 research outputs found

    Thermopower and thermoelectric power factor of Zk{\mathbb Z}_k parafermion quantum dots

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    Using the conformal field theory approach to the thermoelectric characteristics of fractional quantum Hall states, previously developed in Nucl. Phys. B 894 (2015) 284, we show that the thermoelectric power factor of Coulomb-blockaded islands, realized by point contacts in Fabry--P\'erot interferometers in the Zk\mathbb{Z}_k parafermion Hall states, could give reliable signatures for distinguishing the topological orders of different quantum Hall states having identical electric properties. For example, while the conductance peak patterns in the Coulomb blockade regime for such states are practically indistinguishable for vn‚Č™vcv_n \ll v_c even at finite temperature, where vnv_n and vcv_c are the Fermi velocities of the neutral and charged modes respectively, the power factors PT\mathcal{P}_T of the corresponding states are much more sensitive to the neutral modes. In particular, the smaller r=vn/vcr=v_n/v_c the bigger the asymmetries in the power factor which combined with the thermal broadening of the conductance peaks due to the neutral modes' multiplicities could give us the ultimate tool to figure out which of the competing quantum Hall universality classes are indeed realized in the experiments. We give a complete description of the power factor profiles in the Z3\mathbb{Z}_3 and Z4\mathbb{Z}_4 parafermion states with arbitrary number of quasiparticles localized in the bulk which could be useful for comparison with the experiments.Comment: 27 pages, 12 PDF figures; v2: added two more references and corrected several misprint

    Thermoelectric properties of Coulomb-blockaded fractional quantum Hall islands

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    We show that it is possible and rather efficient to compute at non-zero temperature the thermoelectric characteristics of Coulomb blockaded fractional quantum Hall islands, formed by two quantum point contacts inside of a Fabry-Perot interferometer, using the conformal field theory partition functions for the chiral edge excitations. The oscillations of the thermopower with the variation of the gate voltage as well as the corresponding figure-of-merit and power factors, provide finer spectroscopic tools which are sensitive to the neutral multiplicities in the partition functions and could be used to distinguish experimentally between different universality classes. We also propose a procedure for measuring the ratio r=v_n/v_c of the Fermi velocities of the neutral and charged edge modes for filling factor \nu=5/2 from the power-factor data in the low-temperature limit.Comment: 27 pages, 12 figure

    The cosmic ray differential diurnal variation dependences on the zenith angle and the geomagnetic disturbance

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    Simultaneous and continuous muon measurements in two opposite azimuthal directions under equal zenith angles demonstrated the importance of this method for cosmic ray diurnal variation investigations. Lately these measurements were extended by means of improved telescopes. The obtained cosmic ray diurnal variations were presented as intensity differential curves. Theoretical investigations connected the properties of these curves with some interplanetary spece parameters. The harmonics of these curves were interpreted physically. Some order difference curves were introduced. In earlier works some dependences between the parameters characterizing the first and the second harmonics of the differential intensity curves and the geomagnetic activity were found. Then all measurements were carried out under only one zenith angle. The results of investigations of similar dependences using data of simultaneous measurements under three different zenith angles are presented

    A universal conformal field theory approach to the chiral persistent currents in the mesoscopic fractional quantum Hall states

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    We propose a general and compact scheme for the computation of the periods and amplitudes of the chiral persistent currents, magnetizations and magnetic susceptibilities in mesoscopic fractional quantum Hall disk samples threaded by Aharonov--Bohm magnetic field. This universal approach uses the effective conformal field theory for the edge states in the quantum Hall effect to derive explicit formulas for the corresponding partition functions in presence of flux. We point out the crucial role of a special invariance condition for the partition function, following from the Bloch-Byers-Yang theorem, which represents the Laughlin spectral flow. As an example we apply this procedure to the Z_k parafermion Hall states and show that they have universal non-Fermi liquid behavior without anomalous oscillations. For the analysis of the high-temperature asymptotics of the persistent currents in the parafermion states we derive the modular S-matrices constructed from the S matrices for the u(1) sector and that for the neutral parafermion sector which is realized as a diagonal affine coset.Comment: 45 pages, LaTeX2e, 4 EPS figures, 1 table, for related color figures see http://theo.inrne.bas.bg/~lgeorg/PF_k.htm

    Aharonov-Bohm effect in the non-Abelian quantum Hall fluid

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    The nu=5/2 fractional quantum Hall effect state has attracted great interest recently, both as an arena to explore the physics of non-Abelian quasiparticle excitations, and as a possible architecture for topological quantum information processing. Here we use the conformal field theoretic description of the Moore-Read state to provide clear tunneling signatures of this state in an Aharonov-Bohm geometry. While not probing statistics directly, the measurements proposed here would provide a first, experimentally tractable step towards a full characterization of the 5/2 state.Comment: 5 pages, 3 figures, 2 tables, added one more figure and conductances formulae for the three channel
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