Tunable nonadiabatic excitation in a single-electron quantum dot.
ABSTRACT We report the observation of nonadiabatic excitations of single electrons in a quantum dot. Using a tunable-barrier single-electron pump, we have developed a way of reading out the excitation spectrum and level population of the dot by using the pump current as a probe. When the potential well is deformed at subnanosecond time scales, electrons are excited to higher levels. In the presence of a perpendicular magnetic field, the excited states follow a Fock-Darwin spectrum. Our experiments provide a simple model system to study nonadiabatic processes of quantum particles.
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ABSTRACT: We study the evolution of a single-electron packet of Lorentzian shape along an edge of the integer quantum Hall regime or in a Mach-Zehnder interferometer, considering a capacitive Coulomb interaction and using a bosonization approach. When the packet propagates along a chiral quantum Hall edge, we find that its electron density profile becomes more distorted from Lorentzian due to the generation of electron-hole excitations, as the interaction strength increases yet stays in a weak interaction regime. However, as the interaction strength becomes larger and enters a strong interaction regime, the distortion becomes weaker and eventually the Lorentzian packet shape is recovered. The recovery of the packet shape leads to an interesting feature of the interference visibility of the symmetric Mach-Zehnder interferometer whose two arms have the same interaction strength. As the interaction strength increases, the visibility decreases from the maximum value in the weak interaction regime, and then increases to the maximum value in the strong interaction regime. We argue that this counterintuitive result also occurs under other types of interactions.Physical review. B, Condensed matter 04/2013; 86(23). · 3.77 Impact Factor
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ABSTRACT: We demonstrate the energy- and time-resolved detection of single-electron wave packets from a clock-controlled source transmitted through a high-energy quantum Hall edge channel. A quantum dot source is loaded with single electrons which are then emitted ∼150 meV above the Fermi energy. The energy spectroscopy of emitted electrons indicates that at high magnetic field these electrons can be transported over several microns without inelastic electron-electron or electron-phonon scattering. Using a time-resolved spectroscopic technique, we deduce the wave packet size at picosecond resolution. We also show how this technique can be used to switch individual electrons into different electron waveguides (edge channels).Physical Review Letters 11/2013; 111(21):216807. · 7.73 Impact Factor
Article: Noise of a single-electron emitter[Show abstract] [Hide abstract]
ABSTRACT: I analyze the correlation function of currents generated by the periodically driven quantum capacitor emitting single electrons and holes into the chiral waveguide. I compare adiabatic and non-adiabatic, transient working regimes of a single-electron emitter and find the striking difference between the correlation functions in two regimes. Quite generally for the system driven with frequency $\Omega$ the correlation function depends on two frequencies, $\omega$ and $\ell \Omega - \omega$, where $\ell$ is an integer. For the emitter driven non-adiabatically the correlation functions for different $\ell$ are similar and almost symmetric in $\omega$. While in the case of adiabatic drive the correlation functions for $\ell \ne 0$ are highly asymmetric in $\omega$ and exceed significantly the one corresponding to $\ell = 0$. Under optimal operating conditions the correlation function for odd $\ell$ is zero.Physical Review B 04/2013; 88(3). · 3.66 Impact Factor