3,107 research outputs found

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

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 $\mathbb{Z}_k$ 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 $v_n \ll v_c$ even at finite temperature,
where $v_n$ and $v_c$ are the Fermi velocities of the neutral and charged modes
respectively, the power factors $\mathcal{P}_T$ of the corresponding states are
much more sensitive to the neutral modes. In particular, the smaller
$r=v_n/v_c$ 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
$\mathbb{Z}_3$ and $\mathbb{Z}_4$ 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

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

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

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

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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