10,697 research outputs found
Quaternionic factorization of the Schroedinger operator and its applications to some first order systems of mathematical physics
We consider the following first order systems of mathematical physics.
1.The Dirac equation with scalar potential. 2.The Dirac equation with
electric potential. 3.The Dirac equation with pseudoscalar potential. 4.The
system describing non-linear force free magnetic fields or Beltrami fields with
nonconstant proportionality factor. 5.The Maxwell equations for slowly changing
media. 6.The static Maxwell system.
We show that all this variety of first order systems reduces to a single
quaternionic equation the analysis of which in its turn reduces to the solution
of a Schroedinger equation with biquaternionic potential. In some important
situations the biquaternionic potential can be diagonalized and converted into
scalar potentials
Instability of the Two-Dimensional Metallic Phase to Parallel Magnetic Field
We report on magnetotransport studies of the unusual two-dimensional metallic
phase in high mobility Si-MOS structures. We have observed that the magnetic
field applied in the 2D plane suppresses the metallic state, causing the
resistivity to increase dramatically by more than 30 times. Over the total
existence range of the metallic state, we have found three distinct types of
the magnetoresistance, related to the corresponding quantum corrections to the
conductivity. Our data suggest that the unusual metallic state is a consequence
of both spin- and Coulomb-interaction effects.Comment: 6 pages, Latex, 4 ps fig
A New Liquid Phase and Metal-Insulator Transition in Si MOSFETs
We argue that there is a new liquid phase in the two-dimensional electron
system in Si MOSFETs at low enough electron densities. The recently observed
metal-insulator transition results as a crossover from the percolation
transition of the liquid phase through the disorder landscape in the system
below the liquid-gas critical temperature. The consequences of our theory are
discussed for variety of physical properties relevant to the recent
experiments.Comment: 12 pages of RevTeX with 3 postscript figure
Scaling and the Metal-Insulator Transition in Si/SiGe Quantum Wells
The existence of a metal-insulator transition at zero magnetic field in two-
dimensional electron systems has recently been confirmed in high mobility
Si-MOSFETs. In this work, the temperature dependence of the resistivity of
gated Si/SiGe/Si quantum well structures has revealed a similar metal-
insulator transition as a function of carrier density at zero magnetic field.
We also report evidence for a Coulomb gap in the temperature dependence of
the resistivity of the dilute 2D hole gas confined in a SiGe quantum well.
In addition, the resistivity in the insulating phase scales with a single
parameter, and is sample independent. These results are consistent with the
occurrence of a metal-insulator transition at zero magnetic field in SiGe
square quantum wells driven by strong hole-hole interactions.Comment: 3 pages, 3 figures, LaTe
Addendum to "Coherent radio pulses from GEANT generated electromagnetic showers in ice"
We reevaluate our published calculations of electromagnetic showers generated
by GEANT 3.21 and the radio frequency pulses they produce in ice. We are
prompted by a recent report showing that GEANT 3.21-modeled showers are
sensitive to internal settings in the electron tracking subroutine. We report
the shower and pulse characteristics obtained with different settings of GEANT
3.21 and with GEANT 4. The default setting of electron tracking in GEANT 3.21
we used in previous work speeds up the shower simulation at the cost of
information near the end of the tracks. We find that settings tracking electron
and positron to lower energy yield a more accurate calculation, a more intense
shower, and proportionately stronger radio pulses at low frequencies. At high
frequencies the relation between shower tracking algorithm and pulse spectrum
is more complex. We obtain radial distributions of shower particles and phase
distributions of pulses from 100 GeV showers that are consistent with our
published results.Comment: 4 pages, 3 figure
Flow diagram of the metal-insulator transition in two dimensions
The discovery of the metal-insulator transition (MIT) in two-dimensional (2D)
electron systems challenged the veracity of one of the most influential
conjectures in the physics of disordered electrons, which states that `in two
dimensions, there is no true metallic behaviour'; no matter how weak the
disorder, electrons would be trapped and unable to conduct a current. However,
that theory did not account for interactions between the electrons. Here we
investigate the interplay between the electron-electron interactions and
disorder near the MIT using simultaneous measurements of electrical resistivity
and magnetoconductance. We show that both the resistance and interaction
amplitude exhibit a fan-like spread as the MIT is crossed. From these data we
construct a resistance-interaction flow diagram of the MIT that clearly reveals
a quantum critical point, as predicted by the two-parameter scaling theory
(Punnoose and Finkel'stein, Science 310, 289 (2005)). The metallic side of this
diagram is accurately described by the renormalization group theory without any
fitting parameters. In particular, the metallic temperature dependence of the
resistance sets in when the interaction amplitude reaches gamma_2 = 0.45 - a
value in remarkable agreement with the one predicted by the theory.Comment: as publishe
Metal-insulator transition in disordered 2DEG including temperature effects
We calculate self-consistently the mutual dependence of electron correlations
and electron-defect scattering for a two dimensional electron gas at finite
temperature. We employ an STLS approach to calculate the electron correlations
while the electron scattering rate off Coulombic impurities and surface
roughness is calculated using self-consistent current-relaxation theory. The
methods are combined and self-consistently solved. We discuss a metal-insulator
transition for a range of disorder levels and electron densities. Our results
are in good agreement with recent experimental observations.Comment: 4 pages, RevTeX + epsf, 5 figure
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