258 research outputs found
Magnetotransport in dilute 2D Si-MOSFET system
The beating pattern of Shubnikov-de Haas oscillations is reproduced in both
the crossed and tilted magnetic field configuration and in presence of
zero-field valley splitting in Si-MOSFET system. The consequences of IQHE in
extremely dilute 2DEG are discussed.Comment: 4 pages, 4 figure
Weak anisotropy and disorder dependence of the in-plane magnetoresistance in high mobility (100) Si-inversion layers
We report studies of the magnetoresistance (MR) in a two-dimensional electron
system in (100) Si-inversion layers, for perpendicular and parallel
orientations of the current with respect to the magnetic field in the 2D-plane.
The magnetoresistance is almost isotropic; this result does not support the
suggestion of the orbital origin of the MR in Si-inversion layer. In the
hopping regime, however, the MR contains a weak anisotropic component that is
non-monotonic in magnetic field. We found that the field, at which the MR
saturates, for different samples varies by a factor of two, being lower or
higher than the field of complete spin polarization of free carriers.
Therefore, the saturation of the MR can not be identified with the spin
polarization of free carriers.Comment: 4 pages, 4 figures; New data adde
Weak Field Hall Resistance and Effective Carrier Density Through Metal-Insulator Transition in Si-MOS Structures
We studied the weak field Hall voltage in 2D electron layers in Si-MOS
structures with different mobilities, through the metal-insulator transition.
In the vicinity of the critical density on the metallic side of the transition,
we have found weak deviations (about 6-20 %) of the Hall voltage from its
classical value. The deviations do not correlate with the strong temperature
dependence of the diagonal resistivity rho_{xx}(T). The smallest deviation in
R_{xy} was found in the highest mobility sample exhibiting the largest
variation in the diagonal resistivity \rho_{xx} with temperature (by a factor
of 5).Comment: 4 pages, 4 figures, RevTe
On the Cooling of Electrons in a Silicon Inversion Layer
The cooling of two-dimensional electrons in silicon-metal-oxide semiconductor
field effect transistors is studied experimentally. Cooling to the lattice is
found to be more effective than expected from the bulk electron-phonon coupling
in silicon. Unexpectedly, the extracted heat transfer rate to phonons at low
temperatures depends cubically on electron temperature, suggesting that
piezoelectric coupling (absent in bulk silicon) dominates over deformation
potential. According to our findings, at 100 mK, electrons farther than 0.1 mm
from the contacts are mostly cooled by phonons. Using long devices and low
excitation voltage we measure electron resistivity down to 100 mK and find that
some of the "metallic" curves, reported earlier, turn insulating below about
300 mK. This finding renders the definition of the claimed 2D metal-insulator
transition questionable. Previous low temperature measurements in silicon
devices are analyzed and thumb rules for evaluating their electron temperatures
are provided.Comment: 5 pages, 4 figures. Discussion corrected and a few references adde
Measurements of the magnetic properties of conduction electrons
We consider various methods and techniques for measuring electron
magnetization and susceptibility, which are used in experimental condensed
matter physics. The list of considered methods for macroscopic measurements
includes magnetomechanic, electromagnetic, modulation-type, and also
thermodynamic methods based on the chemical potential variation. We also
consider local methods of magnetic measurements based on the spin Hall effects
and NV-centers. Several scanning probe magnetometers-microscopes are
considered, such as magnetic resonance force microscope, SQUID-microscope, and
Hall microscope. The review focuses on the spin magnetization measurements of
electrons in non-magnetic materials and artificial systems, particularly, in
low-dimensional electron systems in semiconductors and in nanosystems, which
came to the forefront in recent years.Comment: 31 pages, 26 figures. To appear in: Phys.Us
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