97 research outputs found
Probing local electronic states in the quantum Hall regime with a side coupled quantum dot
We demonstrate a new method for locally probing the edge states in the
quantum Hall regime utilizing a side coupled quantum dot positioned at an edge
of a Hall bar. By measuring the tunneling of electrons from the edge states
into the dot, we acquire information on the local electrochemical potential and
electron temperature of the edge states. Furthermore, this method allows us to
observe the spatial modulation of the electrostatic potential at the edge state
due to many-body screening effect.Comment: 5 pages, 5 figure
Anisotropic Behavior of the Thermoelectric Power and the Thermal Conductivity in a Unidirectional Lateral Superlattice: A Typical Anisotropic System Exhibiting Two Distinct Nernst Coefficients
We have calculated the thermoelectric conductivity tensor
and the thermal conductivity tensor of a unidirectional lateral
superlattice (ULSL) (, with the -axis aligned to the principal
axis of the ULSL), %, given as the first- and the second-order moments,
employing based on the asymptotic analytic formulas of the electrical
conductivity tensor in the literature valid at low magnetic
fields where large numbers of Landau levels are occupied. With the resulting
analytic expressions, we clarify the conditions for the Mott formula
(Wiedemann-Franz law) to be applicable with high precision to
(). We further present plots of the
commensurability oscillations , ,
, and in , ,
(an alternative, more standard definition of) the thermal conductivity tensor
, and the thermopower tensor , calculated using typical
parameters for a ULSL fabricated from a GaAs/AlGaAs two-dimensional electron
gas (2DEG). Notable features of the are (i) anisotropic
behavior () and (ii) the dominance of the
component over the other components (). The latter clearly indicates that the two
Nernst coefficients, and , can be totally different from each
other in an anisotropic system. Both (i) and (ii) are at variance with the
previous theory and are attributable to the inclusion of a damping factor due
to the small-angle scattering characteristic of GaAs/AlGaAs 2DEGs, which have
not been taken into consideration in thus far.Comment: 14 pages, 9 figures, Title and Introduction altered to make the main
point of the paper clearer. Minor revisions throughout the paper. Some
additions to the IV Discussion. Explicit energy dependence of the
zero-temperature conductivity newly presented in the Appendi
Detection of spin polarization with a side coupled quantum dot
We propose realistic methods to detect local spin polarization, which utilize
a quantum dot side coupled to the target system. By choosing appropriate states
in the dot, we can put spin selectivity to the dot and detect spins in the
target with small disturbance. We also present an experiment which realizes one
of the proposed spin detection schemes in magnetic fields.Comment: 5 pages, 6 figure
Observation of the Fano-Kondo Anti-Resonance in a Quantum Wire with a Side-Coupled Quantum Dot
We have observed the Fano-Kondo anti-resonance in a quantum wire with a
side-coupled quantum dot. In a weak coupling regime, dips due to the Fano
effect appeared. As the coupling strength increased, conductance in the regions
between the dips decreased alternately. From the temperature dependence and the
response to the magnetic field, we conclude that the conductance reduction is
due to the Fano-Kondo anti-resonance. At a Kondo valley with the Fano parameter
, the phase shift is locked to against the gate voltage
when the system is close to the unitary limit in agreement with theoretical
predictions by Gerland {\it et al.} [Phys. Rev. Lett. {\bf 84}, 3710 (2000)].Comment: 4 pages, 4 figure
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