We have investigated the noise properties of the tunneling current through vertically coupled self-assembled InAs quantum dots. We observe super-Poissonian shot noise at low temperatures. For increased temperature this effect is suppressed. The super-Poissonian noise is explained by capacitive coupling between different stacks of quantum dots.

We investigate the noise properties of a zero-dimensional InAs quantum dot (QD) embedded in a GaAs-AlAs-GaAs tunneling structure. We observe an approximately linear dependence of the Fano factor and the current as function of bias voltage. Both effects can be linked to the scanning of the 3-dimensional emitter density of states by the QD. At the current step the shape of the Fano factor is mainly determined by the Fermi function of the emitter electrons. The observed voltage and temperature dependence is compared to the results of a master equation approach.

We study the noise properties of a gate controlled single electron pump at a driving frequency fp=400MHz. We observe a significant reduction of the noise power on the current plateaus. This is a strong indication for true quantized charge pumping. We furthermore observe a small level of low frequency fluctuations which indicates a good frequency stability of the pump.

We present noise measurements of self-assembled InAs quantum dots at high magnetic field. In comparison to I-V characteristics at zero magnetic field, we notice a strong current overshoot that is due to a Fermi-edge singularity. We observe an enhanced suppression in the shot noise power simultaneous to the current overshoot that is attributed to the electron-electron interaction at the Fermi-edge singularity. DOI: 10.1103/PhysRevB.75.233304 PACS number͑s͒: 73.63.Kv, 72.70.ϩm, 73.40.Gk The measurement of shot noise provides information that cannot be extracted from conductance measurements alone. 1It has its origin in time dependent fluctuations of the electrical current due to the discreteness of the charge. For an uncorrelated flow of electrons, the shot noise power S induced by individual tunneling events is proportional to the stationary current I and the absolute charge of the electrons, S =2eI.2 Interactions between the electrons, e.g., Coulomb interaction or Pauli exclusion principle, can reduce 3,4 or enhance 5,6 the shot noise power in resonant tunneling devices. For tunneling through zero dimensional states, which form in the so-called quantum dots, it has been shown both theoretically and experimentally that the shot noise power S is suppressed down to half its normal value, 7-12 eI ഛ S ഛ 2eI. Recently, deviations in the shot noise power from the previous values have been proposed due to certain electronelectron interaction effects, such as the Kondo effect 13-15 or cotunneling. 16Motivated by these results, we present temperature dependent noise measurements of self-assembled InAs quantum dots under the influence of a high magnetic field, leading to another electron-electron interaction effect, a so-called Fermi-edge singularity effect. This effect is caused by an interaction induced rearrangement of the states in the lead at the resonance of the dot level with the emitter lead Fermi energy. This results in an increased tunneling rate. Its dominant observable feature is a strong overshoot in the current at certain values of the bias voltage. [17][18][19][20] This overshoot is accompanied by a suppression of the measured shot noise. 21 We examine this effect in detail and find that this suppression is stronger than expected and reveals the interaction effect between the lead and the dot.The active part of the investigated sample consists of a GaAs-AlAs-GaAs heterostructure with a cross section of 9 ϫ 9 m 2 . N-doped GaAs acts as three-dimensional emitter and collector. Situated inside the AlAs are 1.8 monolayers InAs. Due to the Stranski-Krastanov growth mechanism, InAs quantum dots ͑QDs͒ are formed with a density of Ϸ220/ m 2 ; only a small fraction participate in electronic transport. 22 The lower and upper AlAs tunneling barriers are 4 and 6 nm thick, respectively. Since transmission electron microscopy images show that the QDs have a height of 2 -3 nm, the effective thickness of the AlAs barrier on top of the QDs is reduced to 3 -4 nm.The sample is inserted into a 3 He system. This allows us to...

Studies of non-equilibrium current fluctuations enable assessing correlations involved in quantum transport through nanoscale conductors. They provide additional information to the mean current on charge statistics and the presence of coherence, dissipation, disorder, or entanglement. Shot noise, being a temporal integral of the current autocorrelation function, reveals dynamical information. In particular, it detects presence of non-Markovian dynamics, i.e., memory, within open systems, which has been subject of many current theoretical studies. We report on low-temperature shot noise measurements of electronic transport through InAs quantum dots in the Fermi-edge singularity regime and show that it exhibits strong memory effects caused by quantum correlations between the dot and fermionic reservoirs. Our work, apart from addressing noise in archetypical strongly correlated system of prime interest, discloses generic quantum dynamical mechanism occurring at interacting resonant Fermi edges.