We present a current and charge conserving theory for the low frequency admittance of a quantum point contact. We derive expressions for the electrochemical capacitance and the displacement current. The latter is determined by the emittance which equals the ca-pacitance only in the limit of vanishing transmission. With the opening of channels the capacitance and the emittance decrease in a step...

We present numerical calculations of the conductance of an interface between a phase-coherent twodimensional electron gas and a superconductor with a quantum point contact in the normal region. Using a scattering matrix approach we reconsider the geometry of De Raedt, Michielsen, and Klapwijk @Phys. Rev. B 50, 631 ~1994!# which was studied within the time-dependent Bogoliubov–de Gennes formalis...

In a quantum Hall ferromagnet, the spin polarization of the two-dimensional electron system can be dynamically transferred to nuclear spins in its vicinity through the hyperfine interaction. The resulting nuclear field typically acts back locally, modifying the local electronic Zeeman energy. Here we report a nonlocal effect arising from the interplay between nuclear polarization and the spatia...

Low-temperature transport experiments on a p-type GaAs quantum dot capacitively coupled to a quantum point contact are presented. The time-averaged as well as time-resolved detection of charging events of the dot are demonstrated and they are used to extract the tunneling rates into and out of the quantum dot. The extracted rates exhibit a super-linear enhancement with the bias applied across t...

We consider the counting statistics of electron transport through a double quantum dot with special emphasis on the dephasing induced by a nearby charge detector. The double dot is embedded in a dissipative enviroment, and the presence of electrons on the double dot is detected with a nearby quantum point contact. Charge transport through the double dot is governed by a non-Markovian generalize...

We have studied the THz magneto-photoresponse of a 2DEG in an InAs quantum well with an embedded Quantum Point Contact in the frequency/field region where electron cyclotron resonance (CR) dominates the response. The photoresponse near CR is manifested as an envelope of the amplitude of the Shubnikov-de Haas oscillations of the 2DEG with a peak near the CR field. Clear spin-splitting of the qua...

We study a quantum point contact in a quantum spin Hall insulator. It has recently been shown that the Luttinger liquid theory of such a structure maps to the theory of a weak link in a Luttinger liquid with spin with Luttinger liquid parameters g =1 /g =g 1. We show that for weak interactions, 1 /2 g 1, the pinch-off of the point contact as a function of gate voltage is controlled by a novel q...

We report on direct measurements of the electronic shot noise of a quantum point contact at frequencies nu in the range 4-8 GHz. The very small energy scale used ensures energy independent transmissions of the few transmitted electronic modes and their accurate knowledge. Both the thermal energy and the quantum point contact drain-source voltage V_{ds} are comparable to the photon energy hnu le...

We report the noise characteristics of quantum point contacts between 100 Hz and 100 kHz at 4.2 K. The noise consists of a 111 component on top of a white background. The 1I/noise increases as the contact width decreases and shows peaks between the quantized resistance plateaus. The white noise background increases with current but is much lower than the fuB shot noise level, suggesting that sh...