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Is inelastic cotunneling phase coherent?a)
a)This paper is based on a talk presented by the authors at the 28th International Conference on the Physics of Semiconductors, which was held 24–28 July 2006, in Vienna, Austria. Contributed papers for that conference may be found in “Physics of Semiconductors: 28th International Conference on the Physics of Semiconductors,” AIP Conference Proceedings No. 893 (AIP, Melville, NY, 2007); see http://proceedings.aip.org/proceedings/confproceed/893.jsp
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10.1063/1.2722725
/content/aip/journal/jap/101/8/10.1063/1.2722725
http://aip.metastore.ingenta.com/content/aip/journal/jap/101/8/10.1063/1.2722725
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

(Color online) (a) SFM micrograph of the structure. In-plane gates (white letters), titanium oxide lines (black lines), and top gates (black letters) are indicated. The ring–double-dot system is illustrated by the quantum dots (full circles) and the AB loop (bright lines through QDs). (b) The conductance from source to drain through the open ring as a function of magnetic field is plotted. For the upper curve the top plunger gate was adjusted to . This allows significant tunneling between the two branches of the ring. For the lower curve the coupling point contact between the branches was closed by applying a more negative voltage of to the top plunger gate. AB oscillations are observed for both curves. (c) The Fourier transform as a function of period is plotted for both top plunger gate settings. An additional AB period for a small orbit is found for the case of coupled branches corresponding to interference around one oxide dot in the structure.

Image of FIG. 2.
FIG. 2.

(Color online) (a) A conductance trace as a function of magnetic field containing weak AB oscillations is plotted (black). The step size of the magnetic field provides about 20 data points per AB period. The superposed curve is composed of the filtered AB signal and the background conductance without the high-frequency part. (b) The filtered AB signal is plotted as a function of magnetic field. It still contains a small varying background due to the finite width of the Gauss window in Fourier space. (c) Subtracting the two curves in (a) yields the high-frequency fluctuations plotted here. Many features are symmetric in magnetic field and therefore reproducible. They mostly originate from interference effects in the contacts of the structure.

Image of FIG. 3.
FIG. 3.

(a) The charge stability diagram of double-dot system as a function of both in-plane plunger gates is shown in the regime of only capacitive coupling between the dots. The dot marks the gate settings for further finite-bias cotunneling measurements. (b) The charge stability diagram of double-dot system as a function of both in-plane plunger gates is shown in the regime of finite tunnel coupling between the dots.

Image of FIG. 4.
FIG. 4.

(Color online) Experiments are performed for only capacitive coupling between the two dots in the cotunneling regime indicated by the black dot in Fig. 3(a). (a) In the upper curve, differential conductance is plotted as a function of DC source-drain voltage averaged over one AB period around zero magnetic field. The inelastic onsets are highlighted. The lower curve shows the phase of the AB oscillations as a function of dc source-drain bias voltage around zero magnetic field. We do not observe a phase jump for every inelastic onset. (b) The filtered AB oscillations with a period of about 22 mT are illustrated as a function of magnetic field and dc bias voltage. Slight shifts of the AB maxima as a function of bias voltage indicate a change in AB period.

Image of FIG. 5.
FIG. 5.

(Color online) Experiments are performed for finite tunnel coupling between the two dots in the cotunneling regime indicated by the black dot in Fig. 3(b). (a) Differential conductance is plotted as a function of magnetic field and dc bias voltage on a nonlinear scale. AB oscillations with a period of about 47 mT are observed corresponding to interference around an oxide dot in the structure. (b) The normalized AB signal is illustrated as a function of magnetic field and dc bias voltage. A phase jump in the AB oscillations is observed across the inelastic onset.

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/content/aip/journal/jap/101/8/10.1063/1.2722725
2007-04-27
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Is inelastic cotunneling phase coherent?a)
http://aip.metastore.ingenta.com/content/aip/journal/jap/101/8/10.1063/1.2722725
10.1063/1.2722725
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