222 research outputs found
Photoinduced magnetism in the ferromagnetic semiconductors
We study the enhancement of the magnetic transition temperature due to
incident light in ferromagnetic semiconductors such as EuS. The photoexcited
carriers mediate an extra ferromagnetic interaction due to the coupling with
the localized magnetic moments. The Hamiltonian consists of a Heisenberg model
for the localized moments and an interaction term between the photoexcited
carriers and the localized moments. The model predicts a small enhancement of
the transition temperature in semi-quantitative agreement with the experiments.Comment: 5 pages, 5 figure
Electrical control of Kondo effect and superconducting transport in a side-gated InAs quantum dot Josephson junction
We measure the non-dissipative supercurrent in a single InAs self-assembled
quantum dot (QD) coupled to superconducting leads. The QD occupation is both
tuned by a back-gate electrode and lateral side-gate. The geometry of the
side-gate allows tuning of the QD-lead tunnel coupling in a region of constant
electron number with appropriate orbital state. Using the side-gate effect we
study the competition between Kondo correlations and superconducting pairing on
the QD, observing a decrease in the supercurrent when the Kondo temperature is
reduced below the superconducting energy gap in qualitative agreement with
theoretical predictions
Tuning the electrically evaluated electron Lande g factor in GaAs quantum dots and quantum wells of different well widths
We evaluate the Lande g factor of electrons in quantum dots (QDs) fabricated
from GaAs quantum well (QW) structures of different well width. We first
determine the Lande electron g factor of the QWs through resistive detection of
electron spin resonance and compare it to the enhanced electron g factor
determined from analysis of the magneto-transport. Next, we form laterally
defined quantum dots using these quantum wells and extract the electron g
factor from analysis of the cotunneling and Kondo effect within the quantum
dots. We conclude that the Lande electron g factor of the quantum dot is
primarily governed by the electron g factor of the quantum well suggesting that
well width is an ideal design parameter for g-factor engineering QDs
Kondo Universal Scaling for a Quantum Dot Coupled to Superconducting Leads
We study competition between the Kondo effect and superconductivity in a
single self-assembled InAs quantum dot contacted with Al lateral electrodes.
Due to Kondo enhancement of Andreev reflections the zero-bias anomaly develops
sidepeaks, separated by the superconducting gap energy Delta. For ten valleys
of different Kondo temperature T_K we tune the gap Delta with an external
magnetic field. We find that the zero-bias conductance in each case collapses
onto a single curve with Delta/kT_K as the only relevant energy scale,
providing experimental evidence for universal scaling in this system.Comment: 4 pages, 3 figure
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