337 research outputs found
Hall magnetoresistivity response under Microwave excitation revisited
We theoretically analyzed the microwave-induced modification of the Hall
magnetoresistivity in high mobility two-dimensional electron systems. These
systems present diagonal magnetoresistivity oscillations and zero-resistance
states when are subjected to microwave radiation. The most surprising
modification of the Hall magnetoresistivity is a periodic reduction which
correlates with a periodic increase in the diagonal resistivity. We present a
model that explains the experimental results considering that radiation affects
directly only the diagonal resistivity and the observed Hall resistivity
changes are coming from the tensor relationship between both of them.Comment: 3 pages, 2 figure
Magnetoresistivity Modulated Response in Bichromatic Microwave Irradiated Two Dimensional Electron Systems
We analyze the effect of bichromatic microwave irradiation on the
magnetoresistivity of a two dimensional electron system. We follow the model of
microwave driven Larmor orbits in a regime where two different microwave lights
with different frequencies are illuminating the sample ( and ).
Our calculated results demonstrate that now the electronic orbit centers are
driven by the superposition of two harmonic oscillatory movements with the
frequencies of the microwave sources. As a result the magnetoresisitivity
response presents modulated pulses in the amplitude with a frequency of
, whereas the main response oscillates with
.Comment: 4 pages, 3 figures Accepted in Applied Physics Letter
From zero resistance states to absolute negative conductivity in microwave irradiated 2D electron systems
Recent experimental results regarding a 2D electron gas subjected to
microwave radiation reveal that magnetoresistivity, apart from presenting
oscillations and zero resistance states, can evolve to negative values at
minima. In other words, the current can evolve from flowing with no
dissipation, to flow in the opposite direction of the dc bias applied. Here we
present a theoretical model in which the existence of radiation-induced
absolute negative conductivity is analyzed. Our model explains the transition
from zero resistance states to absolute negative conductivity in terms of
multiphoton assisted electron scattering due to charged impurities. It shows as
well, how this transition can be driven by tuning microwave frequency and
intensity. Then it opens the possibility of controlling the electron Larmor
orbits dynamics (magnetoconductivity) in microwave driven nanodevices. The
analysis of zero resistance states is therefore promising because new optical
and transport properties in nanodevices will be expected.Comment: 5 pages and 4 figure
Ferromagnetically coupled magnetic impurities in a quantum point contact
We investigate the ground and excited states of interacting electrons in a
quantum point contact using exact diagonalization method. We find that strongly
localized states in the point contact appear when a new conductance channel
opens due to momentum mismatch. These localized states form magnetic impurity
states which are stable in a finite regime of chemical potential and excitation
energy. Interestingly, these magnetic impurities have ferromagnetic coupling,
which shed light on the experimentally observed puzzling coexistence of Kondo
correlation and spin filtering in a quantum point contact
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