221 research outputs found
Opposing shear senses in a subdetachment mylonite zone: Implications for core complex mechanics
[1] Global studies of metamorphic core complexes and lowâangle detachment faults have highlighted a fundamental problem: Since detachments excise crustal section, the relationship between the mylonitic rocks in their footwalls and the brittle deformation in their hanging walls is commonly unclear. Mylonites could either reflect ductile deformation related to exhumation along the detachment fault, or they could be a more general feature of the extending middle crust that has been âcaptured â by the detachment. In the first case we would expect the kinematics of the mylonite zone to mirror the sense of movement on the detachment; in the second case both the direction and sense of shear in the mylonites could be different. The northern Snake Range dĂ©collement (NSRD) is a classic Basin and Range detachment fault with a wellâdocumented topâeast of displacement. We present structural, paleo-magnetic, geochronological, and geothermometric evidence to suggest that the mylonite zone below the NSRD locally experienced phases of both east â and westâdirected shear, inconsistent with movement along a single detachment fault. We therefore propose that the footwall mylonites represent a predetachment dis-continuity in the middle crust that separated localized deformation above from distributed crustal flow below (localizedâdistributed transition (LDT)). The mylonites were subsequently captured by a moderately dipping brittle detachment that soled down to the middle crust and exhumed them around a rolling hinge into a subhorizontal orientation at the surface, produc-ing the presentâday NSRD. In this interpretation the brittle hanging wall represents a series of rotated upper crustal normal faults, whereas the mylonitic footwall represents one or more exhumed middl
Resonant Inelastic X-Ray Scattering from Valence Excitations in Insulating Copper-Oxides
We report resonant inelastic x-ray measurements of insulating LaCuO
and SrCuOCl taken with the incident energy tuned near the Cu K
absorption edge. We show that the spectra are well described in a shakeup
picture in 3rd order perturbation theory which exhibits both incoming and
outgoing resonances, and demonstrate how to extract a spectral function from
the raw data. We conclude by showing {\bf q}-dependent measurements of the
charge transfer gap.Comment: minor notational changes, discussion of anderson impurity model
fixed, references added; accepted by PR
Magnetoresistance of nondegenerate quantum electron channels formed on the surface of superfluid helium
Transport properties of quasi-one-dimensional nondegenerate quantum wires
formed on the surface of liquid helium in the presence of a normal magnetic
field are studied using the momentum balance equation method and the memory
function formalism. The interaction with both kinds of scatterers available
(vapor atoms and capillary wave quanta) is considered. We show that unlike
classical wires, quantum nondegenerate channels exhibit strong
magnetoresistance which increases with lowering the temperature.Comment: 8 pages, 7 figure
Plasma dispersion of multisubband electron systems over liquid helium
Density-density response functions are evaluated for nondegenerate
multisubband electron systems in the random-phase approximation for arbitrary
wave number and subband index. We consider both quasi-two-dimensional and
quasi-one- dimensional systems for electrons confined to the surface of liquid
helium. The dispersion relations of longitudinal intrasubband and transverse
intersubband modes are calculated at low temperatures and for long wavelengths.
We discuss the effects of screening and two-subband occupancy on the plasmon
spectrum. The characteristic absorption edge of the intersubband modes is
shifted relatively to the single-particle intersubband separation and the
depolarization shift correction can be significant at high electron densities
Tunneling into a two-dimensional electron system in a strong magnetic field
We investigate the properties of the one-electron Green's function in an
interacting two-dimensional electron system in a strong magnetic field, which
describes an electron tunneling into such a system. From finite-size
diagonalization, we find that its spectral weight is suppressed near zero
energy, reaches a maximum at an energy of about , and
decays exponentially at higher energies. We propose a theoretical model to
account for the low-energy behavior. For the case of Coulomb interactions
between the electrons, at even-denominator filling factors such as ,
we predict that the spectral weight varies as , for
Low-Temperature Mobility of Surface Electrons and Ripplon-Phonon Interaction in Liquid Helium
The low-temperature dc mobility of the two-dimensional electron system
localized above the surface of superfluid helium is determined by the slowest
stage of the longitudinal momentum transfer to the bulk liquid, namely, by the
interaction of surface and volume excitations of liquid helium, which rapidly
decreases with temperature. Thus, the temperature dependence of the
low-frequency mobility is \mu_{dc} = 8.4x10^{-11}n_e T^{-20/3} cm^4 K^{20/3}/(V
s), where n_e is the surface electron density. The relation
T^{20/3}E_\perp^{-3} << 2x10^{-7} between the pressing electric field (in
kV/cm) and temperature (in K) and the value \omega < 10^8 T^5 K^{-5}s^{-1} of
the driving-field frequency have been obtained, at which the above effect can
be observed. In particular, E_\perp = 1 kV/cm corresponds to T < 70 mK and
\omega/2\pi < 30 Hz.Comment: 4 pages, 1 figur
Resonant Inelastic X-ray Scattering from Charge and Orbital Excitations in Manganites
We present a theory of the resonant inelastic x-ray scattering (RIXS) to
study electronic excitations in orbital ordered manganites. The charge and
orbital excitations of the Mn 3d electron are caused by the Coulomb
interactions in the intermediate scattering state. The scattering cross section
is formulated by the Liouville operator method where the local and itinerant
natures of the excitations are taken into account on an equal footing. As a
result, the cross section is expressed by the charge and orbital correlation
functions associated with local corrections. The RIXS spectra are calculated
numerically as functions of momentum and polarization of x ray. Through the
calculations, we propose that RIXS provides a great opportunity to study the
unique electronic excitations in correlated electron systems with orbital
degeneracy.Comment: 8 pages, 5 figure
Power of Anisotropic Exchange Interactions: Universality and Efficient Codes for Quantum Computing
We study the quantum computational power of a generic class of anisotropic
solid state Hamiltonians. A universal set of encoded logic operations are found
which do away with difficult-to-implement single-qubit gates in a number of
quantum computer proposals, e.g., quantum dots and donor atom spins with
anisotropic exchange coupling, quantum Hall systems, and electrons floating on
helium.We show how to make the corresponding Hamiltonians universal by encoding
one qubit into two physical qubits, and by controlling nearest neighbor
interactions.Comment: 5 pages, no figures. v4: Title and abstract changed. Added paragraph
on state preparation and measurement. Parafermionic notation replaced with
standard qubit notation. For treatment of qubits as parafermions see
http://xxx.lanl.gov/abs/quant-ph/010907
Structure of the Magneto-Exciton and Optical Properties in Fractional Quantum Hall Systems
We report calculated dependence of magneto-exciton energy spectrum upon
electron-hole separation in Fractional Quantum Hall systems. We calculated
the dependence of photoluminescence upon , and we obtained the doublet
structure observed recently. The Raman scattering spectrum around resonance is
calculated: a robust resonance peak at around gap value is reported.Comment: 13 pages, REVTEX, compressed postscript file (3 figures included
Indirect Interaction of Solid-State Qubits via Two-Dimensional Electron Gas
We propose a mechanism of long-range coherent coupling between nuclear spins
to be used as qubits in solid-state semiconductor-heterojunction quantum
information processing devices. The coupling is via localized donor electrons
which in turn interact with the two-dimensional electron gas. An effective
two-spin interaction Hamiltonian is derived and the coupling strength is
evaluated. We also discuss mechanisms of qubit decoherence and consider
possibilities for gate control of the interaction between neighboring qubits.
The resulting quantum computing scheme retains all the gate-control and
measurement aspects of earlier approaches, but allows qubit spacing at
distances of order 100nm, attainable with the present-day semiconductor device
technologies.Comment: 12 pages in plain Te
- âŠ