504 research outputs found
Charge Detection in a Closed-Loop Aharonov-Bohm Interferometer
We report on a study of complementarity in a two-terminal "closed-loop"
Aharonov-Bohm interferometer. In this interferometer, the simple picture of
two-path interference cannot be applied. We introduce a nearby quantum point
contact to detect the electron in a quantum dot inserted in the interferometer.
We found that charge detection reduces but does not completely suppress the
interference even in the limit of perfect detection. We attribute this
phenomenon to the unique nature of the closed-loop interferometer. That is, the
closed-loop interferometer cannot be simply regarded as a two-path
interferometer because of multiple reflections of electrons. As a result, there
exist indistinguishable paths of the electron in the interferometer and the
interference survives even in the limit of perfect charge detection. This
implies that charge detection is not equivalent to path detection in a
closed-loop interferometer. We also discuss the phase rigidity of the
transmission probability for a two-terminal conductor in the presence of a
detector.Comment: 4 pages with 4 figure
Entanglement, measurement, and conditional evolution of the Kondo singlet interacting with a mesoscopic detector
We investigate various aspects of the Kondo singlet in a quantum dot (QD)
electrostatically coupled to a mesoscopic detector. The two subsystems are
represented by an entangled state between the Kondo singlet and the
charge-dependent detector state. We show that the phase-coherence of the Kondo
singlet is destroyed in a way that is sensitive to the charge-state information
restored both in the magnitude and in the phase of the scattering coefficients
of the detector. We also introduce the notion of the `conditional evolution' of
the Kondo singlet under projective measurement on the detector. Our study
reveals that the state of the composite system is disentangled upon this
measurement. The Kondo singlet evolves into a particular state with a fixed
number of electrons in the quantum dot. Its relaxation time is shown to be
sensitive only to the QD-charge dependence of the transmission probability in
the detector, which implies that the phase information is erased in this
conditional evolution process. We discuss implications of our observations in
view of the possible experimental realization.Comment: Focus issue on "Interference in Mesoscopic Systems" of New J. Phy
Coulomb blockade double-dot Aharonov-Bohm interferometer: giant fluctuations
Electron transport through two parallel quantum dots is a kind of solid-state
realization of double-path interference. We demonstrate that the inter-dot
Coulomb correlation and quantum coherence would result in strong current
fluctuations with a divergent Fano factor at zero frequency. We also provide
physical interpretation for this surprising result, which displays its generic
feature and allows us to recover this phenomenon in more complicated systems.Comment: 5 pages, 4 figure
On Pan-Africanism, Feminism, and Psychotherapy: The Perspectives of Three Black Scholar-Practitioners from the U.S., Uganda, and St. Kitts/U.S
Three African-descended psychologists discuss the case of a psychotherapy dyad in which the first author, a U.S. national, and a Caribbean student who had immigrated to the U.S. served respectively as therapist and client. We discuss the relevance of Helms’ racial identity development theory to the cultivation of psychological health among African-descended women, proposing that this form of health is intimately tied to our association with other African-descended people. With particular focus on the client’s disclosures about certain groups of Black people in stereotypical ways, what we term “othering by the other,” we offer a conceptualization that knits together issues of personal vulnerability, the reproduction of structural violence, and racial identity development. We conclude by presenting our views on the process and outcome of the therapeutic case and the significance of the theory to addressing the violence that continues to disrupt the lives of Black men and women around the world
Beating of Aharonov-Bohm oscillations in a closed-loop interferometer
One of the points at issue with closed-loop-type interferometers is beating
in the Aharonov-Bohm (AB) oscillations. Recent observations suggest the
possibility that the beating results from the Berry-phase pickup by the
conducting electrons in materials with the strong spin-orbit interaction (SOI).
In this study, we also observed beats in the AB oscillations in a gate-defined
closed-loop interferometer fabricated on a GaAs/AlGaAs two-dimensional
electron-gas heterostructure. Since this heterostructure has very small SOI,
the picture of the Berry-phase pickup is ruled out. The observation of beats in
this study, with the controllability of forming a single transverse subband
mode in both arms of our gate-defined interferometer, also rules out the
often-claimed multiple transverse subband effect. It is observed that nodes of
the beats with an h/2e period exhibit a parabolic distribution for varying the
side gate. These results are shown to be well interpreted, without resorting to
the SOI effect, by the existence of two-dimensional multiple longitudinal modes
in a single transverse subband. The Fourier spectrum of measured conductance,
despite showing multiple h/e peaks with the magnetic-field dependence that are
very similar to that from strong-SOI materials, can also be interpreted as the
two-dimensional multiple-longitudinal-modes effect
Metal-Insulator oscillations in a Two-dimensional Electron-Hole system
The electrical transport properties of a bipolar InAs/GaSb system have been
studied in magnetic field. The resistivity oscillates between insulating and
metallic behaviour while the quantum Hall effect shows a digital character
oscillating from 0 to 1 conducatance quantum e^2/h. The insulating behaviour is
attributed to the formation of a total energy gap in the system. A novel looped
edge state picture is proposed associated with the appearance of a voltage
between Hall probes which is symmetric on magnetic field reversal.Comment: 4 pages, 5 Postscript figures: revised versio
Coulomb blockade double-dot Aharonov-Bohm interferometer: harmonic decomposition of the interference pattern
For the solid state double-dot interferometer, the phase shifted interference
pattern induced by the interplay of inter-dot Coulomb correlation and multiple
reflections is analyzed by harmonic decomposition. Unexpected result is
uncovered, and is discussed in connection with the which-path detection and
electron loss.Comment: 5 pages, 3 figure
- …