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Register a new userGiant fluctuations and gate control of the g-factor in InAs Nanowire Quantum Dots
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We study the g-factor of discrete electron states in InAs nanowire based quantum dots. The g values are determined from the magnetic field splitting of the zero bias anomaly due to the spin 1/2-Kondo effect. Unlike to previous studies based on 2DEG quantum dots, the g-factors of neighboring electron states show a surprisingly large fluctuation: g can scatter between 2 and 18. Furthermore electric gate tunability of the g-factor is demonstrated.
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We study the effects of magnetic and electric fields on the g-factors of spins confined in a two-electron InAs nanowire double quantum dot. Spin sensitive measurements are performed by monitoring the leakage current in the Pauli blockade regime. Rotations of single spins are driven using electric-dipole spin resonance. The g-factors are extracted from the spin resonance condition as a function of the magnetic field direction, allowing determination of the full g-tensor. Electric and magnetic field tuning can be used to maximize the g-factor difference and in some cases altogether quench the EDSR response, allowing selective single spin control.
Photoluminescence data from single, self-assembled InAs/InP quantum dots in magnetic fields up to 7 T are presented. Exciton g-factors are obtained for dots of varying height, corresponding to ground state emission energies ranging from 780 meV to 1100 meV. A monotonic increase of the g-factor from -2 to +1.2 is observed as the dot height decreases. The trend is well reproduced by sp3 tight binding calculations, which show that the hole g-factor is sensitive to confinement effects through orbital angular momentum mixing between the light-hole and heavy-hole valence bands. We demonstrate tunability of the exciton g-factor by manipulating the quantum dot dimensions using pyramidal InP nanotemplates.
The knowledge of electron and hole g-factors, their control and engineering are key for the usage of the spin degree of freedom for information processing in solid state systems. The electronic g-factor will be materials dependent, the effect being larger for materials with large spin-orbit coupling. Since electrons can be individually trapped into quantum dots in a controllable manner, they may represent a good platform for the implementation of quantum information processing devices. Here we use self-assembled quantum dots of InAs embedded in GaAs for the g-factor control and engineering.
Semiconducting nanowires (NWs) are a versatile, highly tunable material platform at the heart of many new developments in nanoscale and quantum physics. Here, we demonstrate charge pumping, i.e., the controlled transport of individual electrons through an InAs NW quantum dot (QD) device at frequencies up to $1.3,$GHz. The QD is induced electrostatically in the NW by a series of local bottom gates in a state of the art device geometry. A periodic modulation of a single gate is enough to obtain a dc current proportional to the frequency of the modulation. The dc bias, the modulation amplitude and the gate voltages on the local gates can be used to control the number of charges conveyed per cycle. Charge pumping in InAs NWs is relevant not only in metrology as a current standard, but also opens up the opportunity to investigate a variety of exotic states of matter, e.g. Majorana modes, by single electron spectroscopy and correlation experiments.
Three-dimensional anisotropy of the Lande g-factor and its electrical modulation are studied for single uncapped InAs self-assembled quantum dots (QDs). The g-factor is evaluated from measurement of inelastic cotunneling via Zeeman substates in the QD for various magnetic field directions. We find that the value and anisotropy of the g-factor depends on the type of orbital state which arises from the three-dimensional confinement anisotropy of the QD potential. Furthermore, the g-factor and its anisotropy are electrically tuned by a side-gate which modulates the confining potential.
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