108 research outputs found
Understanding the nature of electronic effective mass in double-doped SrTiO
We present an approach to tune the effective mass in an oxide semiconductor
by a double doping mechanism. We demonstrate this in a model oxide system
SrLaTiO, where we can tune the effective mass ranging
from 6--20 as a function of filling or carrier concentration and
the scattering mechanism, which are dependent on the chosen lanthanum and
oxygen vacancy concentrations. The effective mass values were calculated from
the Boltzmann transport equation using the measured transport properties of
thin films of SrLaTiO. Our method, which shows that
the effective mass decreases with carrier concentration, provides a means for
understanding the nature of transport processes in oxides, which typically have
large effective mass and low electron mobility, contrary to the tradional high
mobility semiconductors.Comment: 5 pages with 4 figure
Negative magneto-resistance of electron gas in a quantum well with parabolic potential
We have studied the electrical conductivity of the electron gas in parallel
electric and magnetic fields directed along the plane of a parabolic quantum
well (across the profile of the potential). We found a general expression for
the electrical conductivity applicable for any magnitudes of the magnetic field
and the degree of degeneration of the electron gas. A new mechanism of
generation of the negative magnetoresistance has been revealed. It has been
shown that in a parabolic quantum well with a non-degenerated electron gas the
negative magnetoresistance results from spin splitting of the levels of the
size quantization.Comment: 15 pages, 3 figure
Oscillations of the Nernst coefficient in bismuth
We calculate the magnetic-field dependence (oscillations) of the Nernst
coefficient in bismuth at low temperatures for the case when the magnetic field
is directed along the trigonal axis of the crystal. In the calculations we take
into account the scattering of the electrons and holes in bismuth on impurities
and the dependence of this scattering on the magnetic field. The results of
these calculations are compared with the experimental data recently published
Diameter-dependent thermopower of Bi nanowires
We present a study of electronic transport in individual Bi nanowires of
large diameter relative to the Fermi wavelength. Measurements of the resistance
and thermopower of intrinsic and Sn-doped Bi wires with various wire diameters,
ranging from 150-480 nm, have been carried out over a wide range of
temperatures (4-300 K) and magnetic fields (0-14 T). We find that the
thermopower of intrinsic Bi wires in this diameter range is positive (type-p)
below about 150 K, displaying a peak at around 40 K. In comparison, intrinsic
bulk Bi is type-n. Magneto-thermopower effects due to the decrease of surface
scattering when the cyclotron diameter is less than the wire diameter are
demonstrated. The measurements are interpreted in terms of a model of diffusive
thermopower, where the mobility limitations posed by hole-boundary scattering
are much less severe than those due to electron-hole scattering.Comment: 32 pages, 12 figures. Previous version replaced to improve
readabilit
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.
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