T. Hatano

Stability diagrams of laterally coupled triple vertical quantum dots in triangular arrangement

We investigate three vertical quantum dots (QDs) laterally coupled in a triangular arrangement forming a triple QD (tQD) with common source and drain electrodes. The three equidistant dot mesas each have one gate electrode allowing control of the electrochemical potential in each QD. From the stability diagrams observed by measuring current through the tQD on sweeping the voltages on two of the gate electrodes for different values of voltage on the third gate electrode, we build up part of the three-dimensional stability diagram. Our device can be useful to reveal the consequences of interdot coupling on electronic states in tQDs.

Single-Dot Spectroscopy via Elastic Single-Electron Tunneling through a Pair of Coupled Quantum Dots

We study the electronic structure of a single self-assembled InAs quantum dot by probing elastic single-electron tunneling through a single pair of weakly coupled dots. In the region below pinch-off voltage, the nonlinear threshold voltage behavior provides electronic addition energies exactly as the linear, Coulomb blockade oscillation does. By analyzing it, we identify the s and the p shell addition spectrum for up to six electrons in the single InAs dot, i.e., one of the coupled dots. The evolution of the shell addition spectrum with magnetic field provides Fock-Darwin spectra of the s and p shells.

Laterally coupled self-assembled InAs quantum dots embedded in resonant tunnel diode with multigate electrodes

We study the electronic properties of submicron vertical resonant tunneling structures containing several self-assembled InAs quantum dots (SADs) surrounded by four gate electrodes. The four gates are designed not only to squeeze the conductive channel containing a few SADs but also to differently modulate the electrochemical potential of each SAD. We measure the stability diagram and distinguish the features of lateral interdot coupling, such as the type of coupling (quantum mechanical or capacitive), the number of coupled dots, and the relative coupled dot position. This technique will be useful in characterizing the electronic properties of coupled SAD systems.

Aharonov-Bohm oscillations changed by indirect interdot tunneling via electrodes in parallel-coupled vertical double quantum dots.

Aharonov-Bohm (AB) oscillations are studied for a parallel-coupled vertical double quantum dot with a common source and drain electrode. We observe AB oscillations of current via a one-electron bonding state as the ground state and an antibonding state as the excited state. As the center gate voltage becomes more negative, the oscillation period is clearly halved for both the bonding and antibonding states, and the phase changes by half a period for the antibonding state. This result can be explained by a calculation that takes account of the indirect interdot coupling via the two electrodes.

Electron transport through Aharonov-Bohm interferometer with laterally coupled double quantum dots

We theoretically investigate electron transport through an Aharonov-Bohm interferometer containing laterally coupled double quantum dots. We introduce the indirect coupling parameter

Semiconductor quantum dots for electron spin qubits

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Intermediate low spin states in a few-electron quantum dot in the v =< 1 regime

, which characterizes the strength of the coupling via the reservoirs between two quantum dots.

Transport properties of a single pair of coupled self-assembled InAs quantum dots

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Fabrication of Si single-electron transistors having double SiO2 barriers

indicates the strongest coupling, where only a single mode contributes to the transport in the system. Two conduction modes exist in a system where

Wigner Distribution Function and Its Application to One-Dimensional Ballistic Channels

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