3,969 research outputs found
Devil's staircase of incompressible electron states in a nanotube
It is shown that a periodic potential applied to a nanotube can lock
electrons into incompressible states. Depending on whether electrons are weakly
or tightly bound to the potential, excitation gaps open up either due to the
Bragg diffraction enhanced by the Tomonaga - Luttinger correlations, or via
pinning of the Wigner crystal. Incompressible states can be detected in a
Thouless pump setup, in which a slowly moving periodic potential induces
quantized current, with a possibility to pump on average a fraction of an
electron per cycle as a result of interactions.Comment: 4 pages, 1 figure, published versio
Caperton\u27s Next Generation: Beyond the Bank
The article looks at a panel discussion on judicial responsibility and the U.S. Supreme Court\u27s decision in \u27Caperton v. A.T. Massey Coal Co.\u27 discussed by several law professionals including Jed Shugerman, Debra Lyn Bassett and Dmitry Bam at a 2014 symposium held in the New York University
Electron properties of carbon nanotubes in a periodic potential
A periodic potential applied to a nanotube is shown to lock electrons into
incompressible states that can form a devil's staircase. Electron interactions
result in spectral gaps when the electron density (relative to a half-filled
Carbon pi-band) is a rational number per potential period, in contrast to the
single-particle case where only the integer-density gaps are allowed. When
electrons are weakly bound to the potential, incompressible states arise due to
Bragg diffraction in the Luttinger liquid. Charge gaps are enhanced due to
quantum fluctuations, whereas neutral excitations are governed by an effective
SU(4)~O(6) Gross-Neveu Lagrangian. In the opposite limit of the tightly bound
electrons, effects of exchange are unimportant, and the system behaves as a
single fermion mode that represents a Wigner crystal pinned by the external
potential, with the gaps dominated by the Coulomb repulsion. The phase diagram
is drawn using the effective spinless Dirac Hamiltonian derived in this limit.
Incompressible states can be detected in the adiabatic transport setup realized
by a slowly moving potential wave, with electron interactions providing the
possibility of pumping of a fraction of an electron per cycle (equivalently, in
pumping at a fraction of the base frequency).Comment: 21 pgs, 8 fig
Solvated dissipative electro-elastic network model of hydrated proteins
Elastic netwok models coarse grain proteins into a network of residue beads
connected by springs. We add dissipative dynamics to this mechanical system by
applying overdamped Langevin equations of motion to normal-mode vibrations of
the network. In addition, the network is made heterogeneous and softened at the
protein surface by accounting for hydration of the ionized residues. Solvation
changes the network Hessian in two ways. Diagonal solvation terms soften the
spring constants and off-diagonal dipole-dipole terms correlate displacements
of the ionized residues. The model is used to formulate the response functions
of the electrostatic potential and electric field appearing in theories of
redox reactions and spectroscopy. We also formulate the dielectric response of
the protein and find that solvation of the surface ionized residues leads to a
slow relaxation peak in the dielectric loss spectrum, about two orders of
magnitude slower than the main peak of protein relaxation. Finally, the
solvated network is used to formulate the allosteric response of the protein to
ion binding. The global thermodynamics of ion binding is not strongly affected
by the network solvation, but it dramatically enhances conformational changes
in response to placing a charge at the active site of the protein
Enhanced Efficiency of Light-Trapping Nanoantenna Arrays for Thin Film Solar Cells
We suggest a novel concept of efficient light-trapping structures for
thin-film solar cells based on arrays of planar nanoantennas operating far from
plasmonic resonances. The operation principle of our structures relies on the
excitation of chessboard-like collective modes of the nanoantenna arrays with
the field localized between the neighboring metal elements. We demonstrated
theoretically substantial enhancement of solar-cell short-circuit current by
the designed light-trapping structure in the whole spectrum range of the
solar-cell operation compared to conventional structures employing
anti-reflecting coating. Our approach provides a general background for a
design of different types of efficient broadband light-trapping structures for
thin-film solar-cell technologically compatible with large-area thin-film
fabrication techniques
Synthesis of SnS nanocrystals by the solvothermal decomposition of a single source precursor
SnS nanocrystals (NCs) were synthesized from bis(diethyldithiocarbamato) tin(II) in oleylamine at elevated temperature. High-resolution transmission electron microscopy (HRTEM) investigation and X-ray diffraction (XRD) analysis showed that the synthesized SnS particles are monocrystalline with an orthorhombic structure. The shape and size tunability of SnS NCs can be achieved by controlling the reaction temperature and time, and the nature of the stabilizing ligands. The comparison between experimental optical band gap values shows evidence of quantum confinement of SnS NCs. Prepared SnS NCs display strong absorption in the visible and near-infrared (NIR) spectral regions making them promising candidates for solar cell energy conversion
Transverse NMR relaxation as a probe of mesoscopic structure
Transverse NMR relaxation in a macroscopic sample is shown to be extremely
sensitive to the structure of mesoscopic magnetic susceptibility variations.
Such a sensitivity is proposed as a novel kind of contrast in the NMR
measurements. For suspensions of arbitrary shaped paramagnetic objects, the
transverse relaxation is found in the case of a small dephasing effect of an
individual object. Strong relaxation rate dependence on the objects' shape
agrees with experiments on whole blood. Demonstrated structure sensitivity is a
generic effect that arises in NMR relaxation in porous media, biological
systems, as well as in kinetics of diffusion limited reactions.Comment: 4 pages, 3 figure
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