3,495 research outputs found
Theory of Polar Corrections to Donor Binding
We calculate the optical phonon correction to the binding energy of electrons
to donors in cubic materials. Previous theories calculated the Rydberg energy
reduced by the effective mass and the static dielectric function. They omitted
an important energy term from the long-range polarization of the ionized donor,
which vanishes for the neutral donor. They also omitted the donor-phonon
interaction. Including these terms yields a new formula for the donor binding
energy
Green's function of a dressed particle
We present a new, highly efficient yet accurate approximation for the Green's
functions of dressed particles, using the Holstein polaron as an example.
Instead of summing a subclass of diagrams (e.g. the non-crossed ones, in the
self-consistent Born approximation (SCBA)), we sum all the diagrams, but with
each diagram averaged over its free propagators' momenta. The resulting Green's
function satisfies exactly the first six spectral weight sum rules. All higher
sum rules are satisfied with great accuracy, becoming asymptotically exact for
coupling both much larger and much smaller than the free particle bandwidth.
Possible generalizations to other models are also discussed.Comment: 4 pages, 3 figure
Evidence of electron fractionalization in the Hall coefficient at Mott criticality
Hall coefficient implies the mechanism for reconstruction of a Fermi surface,
distinguishing competing scenarios for Mott criticality such as electron
fractionalization, dynamical mean-field theory, and metal-insulator transition
driven by symmetry breaking. We find that electron fractionalization leaves a
signature for the Hall coefficient at Mott criticality in two dimensions, a
unique feature differentiated from other theories. We evaluate the Hall
coefficient based on the quantum Boltzman equation approach, guaranteeing gauge
invariance in both longitudinal and transverse transport coefficients
Haldane Sashes in Quantum Hall Spectra
We show that the low-temperature sash features in the lowest Landau-level
(LLL) tunneling density-of-states (TDOS) recently discovered by Dial and
Ashoori are intimately related to the discrete Haldane-pseudopotential
interaction energy scales that govern fractional quantum Hall physics. Our
analysis is based on expressions for the tunneling density-of-states which
become exact at filling factors close to and , where the sash
structure is most prominent. We comment on other aspects of LLL correlation
physics that can be revealed by accurate temperature-dependent tunneling data.Comment: Added referenc
Orbital Polarization in Itinerant Magnets
We propose a parameter-free scheme of calculation of the orbital polarization
(OP) in metals, which starts with the strong-coupling limit for the screened
Coulomb interactions in the random-phase approximation (RPA). For itinerant
magnets, RPA can be further improved by restoring the spin polarization of the
local-spin-density approximation (LSDA) through the local-field corrections.
The OP is then computed in the static GW approach, which systematically
improves the orbital magnetization and the magnetic anisotropy energies in
transition-metal and actinide compounds.Comment: 5 pages, 4 figure
Composite-Fermion Theory for Pseudogap, Fermi Arc, Hole Pocket, and Non-Fermi-Liquid of Underdoped Cuprate Superconductors
We propose that an extension of the exciton concept to doped Mott insulators
offers a fruitful insight into challenging issues of the copper oxide
superconductors. In our extension, new fermionic excitations called cofermions
emerge in conjunction to generalized excitons. The cofermions hybridize with
conventional quasiparticles. Then a hybridization gap opens, and is identified
as the pseudogap observed in the underdoped cuprates. The resultant
Fermi-surface reconstruction naturally explains a number of unusual properties
of the underdoped cuprates, such as the Fermi arc and/or pocket formation.Comment: 9 pages, 8 figure
Electronic transport in ferromagnetic conductors with inhomogeneous magnetic order parameter -- domain-wall resistance
We microscopically derive transport equations for the conduction electrons in
ferromagnetic materials with an inhomogeneous magnetization profile. Our
quantum kinetic approach includes elastic scattering and anisotropic spin-flip
scattering at magnetic impurities. In the diffusive limit, we calculate the
resistance through a domain wall and find that the domain-wall resistance can
be positive or negative. In the limit of long domain walls we derive analytical
expressions and compare them with existing works, which used less general
models or different theoretical frameworks.Comment: 19 Page
Reply to Comment on "Critical analysis of a variational method used to describe molecular electron transport"
We show that the failure of the Delaney-Greer (DG) variational ansatz for
transport demonstrated by us in Phys.\ Rev.\ B {\bf 80}, 165301 (2009) (I) is
not related to an unsuitable constraint that prevents a broken time-reversal
symmetry or to real orbitals, as DG incorrectly claim. The complex orbitals
suggested by them as a way-out solution merely represent a particular case of
the general case considered by us in I, which do not in the least affect our
conclusion.Comment: Manuscript as submitted to Phys. Rev. B on 30 November 2010. Sections
VII, VIII, and IX present significant details, which enlarge the analysis of
the published versio
Giant anharmonicity suppresses superconductivity in AlH under pressure
The anharmonic self energy of two zone boundary phonons were computed to
lowest order for AlH in the structure at 110 GPa. The
wavevector and branch index corresponding to these modes are situated in a
region of phase space providing most of the electron-phonon coupling. The self
energies are found to be very large and the anharmonic contribution to the
linewidth of one of the modes studied could be distinguished from the
electron-phonon linewidth. It is found that anharmonicity suppresses the
electron-phonon coupling parameter , providing a possible explanation
for the disagreement between experiment and previous theoretical studies of
superconductivity in this system.Comment: 10 pages, 4 figure
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