42,944 research outputs found
Thermodynamics of Information Processing Based on Enzyme Kinetics: an Exactly Solvable Model of Information Pump
Motivated by the recent proposed models of the information engine [D. Mandal
and C. Jarzynski, Proc. Natl. Acad. Sci. 109, 11641 (2012)] and the information
refrigerator [D. Mandal, H. T. Quan, and C. Jarzynski, Phys. Rev. Lett. 111,
030602 (2013)], we propose a minimal model of the information pump and the
information eraser based on enzyme kinetics. This device can either pump
molecules against the chemical potential gradient by consuming the information
encoded in the bit stream or (partially) erase the information encoded in the
bit stream by consuming the Gibbs free energy. The dynamics of this model is
solved exactly, and the "phase diagram" of the operation regimes is determined.
The efficiency and the power of the information machine is analyzed. The
validity of the second law of thermodynamics within our model is clarified. Our
model offers a simple paradigm for the investigating of the thermodynamics of
information processing involving the chemical potential in small systems
Andreev Edge State on Semi-Infinite Triangular Lattice: Detecting the Pairing Symmetry in Na_0.35CoO_2.yH_2O
We study the Andreev edge state on the semi-infinite triangular lattice with
different pairing symmetries and boundary topologies. We find a rich phase
diagram of zero energy Andreev edge states that is a unique fingerprint of each
of the possible pairing symmetries. We propose to pin down the pairing symmetry
in recently discovered Na_xCoO_2 material by the Fourier-transformed scanning
tunneling spectroscopy for the edge state. A surprisingly rich phase diagram is
found and explained by a general gauge argument and mapping to 1D tight-binding
model. Extensions of this work are discussed at the end.Comment: 4 pages, 1 table, 4 figure
Double-layer Perfect Metamaterial Absorber and Its Application for RCS Reduction of Antenna
To reduce the radar cross section (RCS) of a circularly polarized (CP) tilted beam antenna, a double-layer perfect metamaterial absorber (DLPMA) in the microwave frequency is proposed. The DLPMA exhibits a wider band by reducing the distance between the three absorption peaks. Absorbing characteristics are analyzed and the experimental results demonstrate that the proposed absorber works well from 5.95 GHz to 6.86 GHz (relative bandwidth 14.1%) with the thickness of 0.5 mm. Then, the main part of perfect electric conductor ground plane of the CP tilted beam antenna is covered by the DLPMA. Simu¬lated and experimental results reveal that the novel antenna performs well from 5.5 GHz to 7 GHz, and its monostatic RCS is reduced significantly from 5.8 GHz to 7 GHz. The agreement between measured and simulated data validates the present design
High- superconductivity in undoped ThFeAsN
Unlike the widely studied ReFeAsO series, the newly discovered iron-based
superconductor ThFeAsN exhibits a remarkably high critical temperature of 30 K,
without chemical doping or external pressure. Here we investigate in detail its
magnetic and superconducting properties via muon-spin rotation/relaxation
(SR) and nuclear magnetic resonance (NMR) techniques and show that ThFeAsN
exhibits strong magnetic fluctuations, suppressed below 35 K, but no magnetic
order. This contrasts strongly with the ReFeAsO series, where stoichiometric
parent materials order antiferromagnetically and superconductivity appears only
upon doping. The ThFeAsN case indicates that Fermi-surface modifications due to
structural distortions and correlation effects are as important as doping in
inducing superconductivity. The direct competition between antiferromagnetism
and superconductivity, which in ThFeAsN (as in LiFeAs) occurs at already zero
doping, may indicate a significant deviation of the -wave superconducting
gap in this compound from the standard scenario.Comment: 6 pages, 5 figure
Anisotropic softening of magnetic excitations in lightly electron doped SrIrO
The magnetic excitations in electron doped (SrLa)IrO with
were measured using resonant inelastic X-ray scattering at the Ir
-edge. Although much broadened, well defined dispersive magnetic
excitations were observed. Comparing with the magnetic dispersion from the
parent compound, the evolution of the magnetic excitations upon doping is
highly anisotropic. Along the anti-nodal direction, the dispersion is almost
intact. On the other hand, the magnetic excitations along the nodal direction
show significant softening. These results establish the presence of strong
magnetic correlations in electron doped SrLa)IrO with close
analogies to the hole doped cuprates, further motivating the search for high
temperature superconductivity in this system
Critical States Embedded in the Continuum
We introduce a class of critical states which are embedded in the continuum
(CSC) of one-dimensional optical waveguide array with one non-Hermitian defect.
These states are at the verge of being fractal and have real propagation
constant. They emerge at a phase transition which is driven by the imaginary
refractive index of the defect waveguide and it is accompanied by a mode
segregation which reveals analogies with the Dicke super -radiance. Below this
point the states are extended while above they evolve to exponentially
localized modes. An addition of a background gain or loss can turn these
localized states to bound states in the continuum.Comment: 4.5 pages, 3 figures, 1 page of supplementary material including one
figur
Transverse momentum dependence in the perturbative calculation of pion form factor
By reanalysing transverse momentum dependence in the perturbative calculation
of pion form factor an improved expression of pion form factor which takes into
account the transverse momentum dependenc in hard scattering amplitude and
intrinsic transverse momentum dependence associated with pion wave functions is
given to leading order, which is available for momentum transfers of the order
of a few GeV as well as for . Our scheme can be extended to
evaluate the contributions to the pion form factor beyond leading order.Comment: 13 pages in LaTeX, plus 3 Postscript figure
Field evolution of the magnetic structures in ErTiO through the critical point
We have measured neutron diffraction patterns in a single crystal sample of
the pyrochlore compound ErTiO in the antiferromagnetic phase
(T=0.3\,K), as a function of the magnetic field, up to 6\,T, applied along the
[110] direction. We determine all the characteristics of the magnetic structure
throughout the quantum critical point at =2\,T. As a main result, all Er
moments align along the field at and their values reach a minimum. Using
a four-sublattice self-consistent calculation, we show that the evolution of
the magnetic structure and the value of the critical field are rather well
reproduced using the same anisotropic exchange tensor as that accounting for
the local paramagnetic susceptibility. In contrast, an isotropic exchange
tensor does not match the moment variations through the critical point. The
model also accounts semi-quantitatively for other experimental data previously
measured, such as the field dependence of the heat capacity, energy of the
dispersionless inelastic modes and transition temperature.Comment: 7 pages; 8 figure
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