Dephasing in Open Quantum Dots

Abstract

Shape-averaged magnetoconductance (weak localization) is used for the first time to obtain the electron phase coherence time t f in open ballistic GaAs quantum dots.Values for t f in the range of temperature T from 0.335 to 4 K are found to be independent of dot area, and are not consistent with the t f µ -T 2 behavior expected for isolated dots. Surprisingly, t f T ( ) agrees quantitatively with the predicted dephasing time for disordered two-dimensional electron systems.Decoherence is the process by which the quantum mechanical properties of a microscopic system are transformed into the familiar classical behavior seen in macroscopic objects. Mesoscopic electronic systems, which exhibit strong coherent quantum mechanical effects such as weak localization and universal conductance fluctuations (UCF), are ideal for investigations of decoherence. The key quantity in these phenomena is the phase coherence time, t f , which determines the energy and length scales at which quantum behavior is seen. Considerable theoretical [1-4] and experimental [5-9] study has been directed toward understanding the mechanisms responsible for the loss of phase coherence (dephasing) and their dependence on temperature, dimensionality, and disorder.Most studies of dephasing in mesoscopic systems have focused on disordered 1Dand 2D conductors, where the dimensional crossover for quantum corrections to transport and interactions responsible for dephasing occurs when the sample width exceeds the phase

Mesoscopic decoherence in Aharonov-Bohm rings

“…In 2D, experiments consistent with the expected 7 electronelectron scattering time τ φ ∼ (T 2 ln T ) −1 has been carried out 3,4 . In open quantum dots (a 0D system), an unexpected T −1 contribution was found 5,6 . In general, phase breaking mechanisms in ballistic, mesoscopic systems of dimensionality less than 2, are presently not well understood.…”

“…In disordered 1D and 2D conductors, the loss of phase coherence at low temperatures has been studied intensively, both theoretically and experimentally 2 . In clean electron systems, the number of investigations are fewer [3][4][5][6] . In 2D, experiments consistent with the expected 7 electronelectron scattering time τ φ ∼ (T 2 ln T ) −1 has been carried out 3,4 .…”

Experimental test of universal conductance fluctuations by means of wave-chaotic microwave cavities

“…Significant theoretical and experimental effort has been devoted to studying the dephasing of the transport electrons in quantum dots [10,11,12]. One class of theoretical dephasing models utilizes a "fictitious voltage probe (φ )" attached to the dot that has a number of channels (modes)…”

Orbital effect of an in-plane magnetic field on quantum transport in chaotic lateral dots

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We show how the in-plane magnetic field, which breaks time-reversal and rotational symmetries of the orbital motion of electrons in a heterostructure due to the momentumdependent inter-subband mixing, affects weak localisation correction to conductance of a large-area chaotic lateral quantum dot and parameteric dependences of universal conductance fluctuations in it.A high sensitivity of phase-coherent transport through quantum dots to external perturbations has recently enabled one to transform studies of mesoscopic effects [1][2][3] into a spectroscopic tool for detecting tiny energetic changes in the electron gas [4] and for studying electron dephasing and inelastic relaxation rates [5,6]. A convenient object [7], once used as a mesoscopic thermometer [8], consists of a lateral semiconductor dot weakly coupled to the reservoirs via two leads, l and r, each with N l,r 1 open conducting channels, and, therefore, quantum conductances g l,r = 2e 2 h N l,r .

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“…A high sensitivity of phase-coherent transport through quantum dots to external perturbations has recently enabled one to transform studies of mesoscopic effects [1][2][3] into a spectroscopic tool for detecting tiny energetic changes in the electron gas [4] and for studying electron dephasing and inelastic relaxation rates [5,6]. A convenient object [7], once used as a mesoscopic thermometer [8], consists of a lateral semiconductor dot weakly coupled to the reservoirs via two leads, l and r, each with N l,r 1 open conducting channels, and, therefore, quantum conductances g l,r = 2e 2 h N l,r .…”