402 research outputs found
Quantization of the Hall conductivity well beyond the adiabatic limit in pulsed magnetic fields
We measure the Hall conductivity, , on a Corbino geometry sample
of a high-mobility AlGaAs/GaAs heterostructure in a pulsed magnetic field. At a
bath temperature about 80 mK, we observe well expressed plateaux in
at integer filling factors. In the pulsed magnetic field, the
Laughlin condition of the phase coherence of the electron wave functions is
strongly violated and, hence, is not crucial for quantization.Comment: 4 pages, 4 figures, submitted to PR
Direct measurements of the spin and the cyclotron gaps in a 2D electron system in silicon
Using magnetocapacitance data in tilted magnetic fields, we directly
determine the chemical potential jump in a strongly correlated two-dimensional
electron system in silicon when the filling factor traverses the spin and the
cyclotron gaps. The data yield an effective g-factor that is close to its value
in bulk silicon and does not depend on filling factor. The cyclotron splitting
corresponds to the effective mass that is strongly enhanced at low electron
densities
Opening an energy gap in an electron double layer system at integer filling factor in a tilted magnetic field
We employ magnetocapacitance measurements to study the spectrum of a double
layer system with gate-voltage-tuned electron density distributions in tilted
magnetic fields. For the dissipative state in normal magnetic fields at filling
factor and 4, a parallel magnetic field component is found to give rise
to opening a gap at the Fermi level. We account for the effect in terms of
parallel-field-caused orthogonality breaking of the Landau wave functions with
different quantum numbers for two subbands.Comment: 4 pages, 4 figures included, to appear in JETP Letter
Spin susceptibility and polarization field in a dilute two-dimensional electron system in (111) silicon
We find that the polarization field, B_chi, obtained by scaling the
weak-parallel-field magnetoresistance at different electron densities in a
dilute two-dimensional electron system in (111) silicon, corresponds to the
spin susceptibility that grows strongly at low densities. The polarization
field, B_sat, determined by resistance saturation, turns out to deviate to
lower values than B_chi with increasing electron density, which can be
explained by filling of the upper electron subbands in the fully spin-polarized
regime
Indication of the ferromagnetic instability in a dilute two-dimensional electron system
The magnetic field B_c, in which the electrons become fully spin-polarized,
is found to be proportional to the deviation of the electron density from the
zero-field metal-insulator transition in a two-dimensional electron system in
silicon. The tendency of B_c to vanish at a finite electron density suggests a
ferromagnetic instability in this strongly correlated electron system.Comment: 4 pages, postscript figures included. Revised versio
Observation of the parallel-magnetic-field-induced superconductor-insulator transition in thin amorphous InO films
We study the response of a thin superconducting amorphous InO film with
variable oxygen content to a parallel magnetic field. A field-induced
superconductor-insulator transition (SIT) is observed that is very similar to
the one in normal magnetic fields. As the boson-vortex duality, which is the
key-stone of the theory of the field-induced SIT, is obviously absent in the
parallel configuration, we have to draw conclusion about the theory
insufficiency.Comment: 3 pages, 4 figure
Nonlocal transport near the charge neutrality point in a two-dimensional electron-hole system
Nonlocal resistance is studied in a two-dimensional system with a
simultaneous presence of electrons and holes in a 20 nm HgTe quantum well. A
large nonlocal electric response is found near the charge neutrality point
(CNP) in the presence of a perpendicular magnetic field. We attribute the
observed nonlocality to the edge state transport via counter propagating chiral
modes similar to the quantum spin Hall effect at zero magnetic field and
graphene near Landau filling factor Comment: 5 pages, 4 figure
- …