4,346 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
Coherent macroscopic quantum tunneling in boson-fermion mixtures
We show that the cold atom systems of simultaneously trapped Bose-Einstein
condensates (BEC's) and quantum degenerate fermionic atoms provide promising
laboratories for the study of macroscopic quantum tunneling. Our theoretical
studies reveal that the spatial extent of a small trapped BEC immersed in a
Fermi sea can tunnel and coherently oscillate between the values of the
separated and mixed configurations (the phases of the phase separation
transition of BEC-fermion systems). We evaluate the period, amplitude and
dissipation rate for Na and K-atoms and we discuss the
experimental prospects for observing this phenomenon.Comment: 4 pages, 3 figure
- …