Single-electron effects in a coupled dot-ring system

Meier, Lorenz; Fuhrer, Andreas; Ihn, Thomas; Ensslin, Klaus; Wegscheider, Werner; Bichler, Max

doi:10.1103/physrevb.69.241302

Cited by 21 publications

(9 citation statements)

References 21 publications

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“…The unperturbed AB-oscillations in Fig. 2 indicate that unlike recently reported results 17,29 we are in a regime where the direct Coulomb interaction between the two structures is negligibly small. Furthermore, the gate on the dot changes neither the characteristic amplitude nor the phase of ABoscillations in the ring over a range ∆V igd ≥ 45 mV.…”

Section: B Coupling the Ring And The Dotcontrasting

confidence: 63%

Fano effect in a quantum-ring–quantum-dot system with tunable coupling

et al. 2006

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Transport measurements are presented on a quantum ring that is tunnel-coupled to a quantum dot. When the dot is in the Coulomb blockade regime, but strongly coupled to the open ring, Fano line shapes are observed in the current through the ring, when the electron number in the dot changes by one. The symmetry of the Fano resonances is found to depend on the magnetic flux penetrating the area of the ring and on the strength of the ring-dot coupling. At temperatures above T=0.65 K the Fano effect disappears while the Aharonov-Bohm interference in the ring persists up to T=4.2 K. Good agreement is found between these experimental observations and a single-channel scattering matrix model including decoherence in the dot.

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Section: B Coupling the Ring And The Dotcontrasting

confidence: 63%

Fano effect in a quantum-ring–quantum-dot system with tunable coupling

et al. 2006

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“…The QPC can thus be used as a non-invasive charge detector [10] in regimes, where direct transport through the quantum dot is experimentally difficult to access. Similarly the central ring struc ture can be used as a charge detector of the dot [11]. Phase-coherent transport through the open ring gives rise to Aharonov-Bohm oscillations in the conductance.…”

Section: Dots and Ringsmentioning

confidence: 99%

Quantum physics in quantum rings

et al. 2005

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T he symmetry of a ring system is crucial for classical and quantum effects. Mathematically speaking a ring is a nonsingly connected geometry. In quantum mechanics the ring symmetry of the benzene molecule gives rise to its delocalized electronic states [1]. In ring geometries strongly connected to external leads the electron wave packets can take two different paths around the ring which gives rise to interference. This is reminiscent of Young's double-slit experiment for photons. The use of charged particles in a ring geometry rather than neutral photons allows the relative phase of the electronic wave function in the two arms of the ring to be manipulated by a magnetic field perpendicular to the plane of the ring. Aharonov and Bohm proposed such a set-up to test experimentally the signifi cance of the magnetic vector potential in quantum mechanics [2]. They predicted that the phase difference of the alternative paths changes by 271 as the flux through the ring is changed by one flux quantum h/q (q is the charge of the particle). Many experiments over the last three decades have demonstrated mag netic field periodic resistance oscillations in ring structures with a phase coherence length longer than or comparable to the perimeter. In mesoscopic physics the Aharonov-Bohm (AB) effect has become a standard tool to quantitatively investigate the phase coherence of transport in metallic [3] and semiconducting systems. In closed systems with fixed electron number a characteristic magnetic flux-periodic energy spectrum evolves. Such a spec trum can be detected experimentally by measuring electron transport through a lithographically defined quantum ring in the Coulomb blockade regime. In ring-shaped confined quantum systems the angular momen tum becomes a good quantum number. In the case of a single mode ring the single-particle energy levels are given by:Here l is the angular momentum quantum number and m is the magnetic quantum number, i.e. the number of flux quanta penetrating the ring at a given external magnetic field. The only material-dependent parameter is the effective mass, m*. The ring radius is denoted by r. At zero magnetic field, m = 0, the ground state has angular momentum l = 0 , the next two degenerate states are characterized by 1 = ± 1 and so forth. At finite magnetic field the ground state develops a finite angular momentu n which can be translated into a persistent current [4]. In this model the wave functions are plane waves extended around the ring independent of magnetic field. Fabrication of quantum ringsIn this article we describe recent experiments on quantum ring: realized in semiconductor heterostructures. Figure 1 shows the Aharonov-Bohm effectAn electron wave coming from the left travels through the ring. The wave propagates in the upper as well as in the lower arm and interferes with itself. The phase accumulation in the upper arm is (ϕ1, in the lower arm (ϕ 2. The phase difference ϕp is determined by a constant depending on the details of the wave propagation in the two arms (ϕ geom) ...

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“…2 They measured the amplitude of the Aharonov-Bohm interference of the ring, and simultaneously detected electron current along a separate circuit containing the dot. The amplitude shows a dip, when the dot has degenerate states with different excess charges and thus shows a Coulomb blockade peak of electron conductance.…”

Section: Introductionmentioning

confidence: 99%

Electronic interferometer capacitively coupled to a quantum dot

2009

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We theoretically study electron interference in a ballistic electronic interferometer capacitively coupled to a quantum dot. The visibility of the interference is reduced when the dot has degenerate ground states with different excess charges. The degree of the reduction depends on system parameters such as the strength of the capacitive coupling, and the dependence is analyzed in the regime where the dwell time of electrons in the dot is much longer than the electron flight time through the interferometry region coupled to the dot. The result is consistent with recent experimental data.Comment: 4 pages, 2 figure

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Single-electron effects in a coupled dot-ring system

Cited by 21 publications

References 21 publications

Fano effect in a quantum-ring–quantum-dot system with tunable coupling

Fano effect in a quantum-ring–quantum-dot system with tunable coupling

Quantum physics in quantum rings

Electronic interferometer capacitively coupled to a quantum dot

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