We study the rectification of voltage fluctuations in a system consisting of two Coulomb-coupled quantum dots. The first quantum dot is connected to a reservoir where voltage fluctuations are supplied and the second one is attached to two separate leads via asymmetric and energy-dependent transport barriers. We observe a rectified output current through the second quantum dot depending quadratically on the noise amplitude supplied to the other Coulomb-coupled quantum dot. The current magnitude and direction can be switched by external gates, and maximum output currents are found in the nA region. The rectification delivers output powers in the pW region. Future devices derived from our sample may be applied for energy harvesting on the nanoscale beneficial for autonomous and energy-efficient electronic applications. DOI: 10.1103/PhysRevLett.114.146805 PACS numbers: 73.23.-b, 73.50.Td, 73.61.Ey, 85.30.-z Extracting work from random fluctuations by energy conversion to a unidirectional particle flow is a key enabling technology and has consequently triggered substantial experimental and theoretical work [1][2][3][4]. The exploitation of temperature and fluctuation gradients for energy harvesting has led to new concepts such as Brownian and Büttiker-Landauer motors [5][6][7][8], phonon rectifiers [9,10], and piezoelectric nanogenerators [11][12][13]. Challenging factors in miniaturizing heat engines are an efficient energy conversion and the maintenance of welldefined hot and cold spots [14]. Quantum dot structures are among the smallest possible heat engines conceived thus far. Pioneering work in this field was conducted by, among others, Molenkamp et al., who measured the Seebeck voltage of single quantum dots (QDs) and quantum point contacts (QPCs) [15][16][17]. In recent years, research concerning heat engines based on QDs and QPCs followed [18][19][20][21][22]. Furthermore, Coulomb-coupled systems attracted attention due to their ability to generate currents in unbiased wires via the Coulomb drag [23][24][25]. A striking proposal combining rectifying effects with QDs was recently made by Sánchez et al., who showed that two capacitively coupled QDs connected to electron reservoirs operated in the Coulomb-blockade regime can act as a rectifier that transfers each energy quantum that passes from one to the other QD to the motion of single electrons (i.e., to charge quanta) [26]. Notably, the heat and charge current directions are decoupled in the proposed system. Later, Sothmann et al. investigated a similar design based on open QD systems (with conductances higher than the conductance quantum) exhibiting higher output currents, which makes this proposal more accessible to experimental realization [27,28]. Furthermore, it combines maximum output power as well as maximum efficiency at the same electrostatic configuration, which is in contrast to Coulomb-blockade systems, where maximum efficiency theoretically occurs at zero output power [26].In this Letter, we present a system that converts voltage fluctuation...

Photocurrent spectroscopy of intersubband transitions in GaInAsN/(Al)GaAs asymmetric quantum well infrared photodetectors

Noise is mostly considered to be an adverse factor in electronics. Yet, effects like logical stochastic resonance (LSR) can render electronic fluctuations useful. Here, we study LSR in a system consisting of two Coulomb-coupled quantum dots (QDs). We observe that voltage fluctuations applied to one of the QDs lead to a rectified and controllable current in the other QD. The interplay between applied noise and gate voltages enables our system to offer logic AND, OR, NAND, and NOR gate functionalities, which can be switched by either a variation of the noise or of a single gate voltage. For an optimal amount of noise, all four functionalities can be toggled by changing solely one single gate voltage. The presented results may prove beneficial for future autonomous, noise-tolerant, and energy-efficient electronics.

We report the optical control of localized charge on positioned quantum dots in an electro-photo-sensitive memristor. Interband absorption processes in the quantum dot barrier matrix lead to photo-generated electron-hole-pairs that, depending on the applied bias voltage, charge or discharge the quantum dots and hence decrease or increase the conductance. Wavelength-dependent conductance control is observed by illumination with red and infrared light, which leads to charging via interband and discharging via intraband absorption, respectively. The presented memristor enables optical conductance control and may thus be considered for sensory applications in artificial neural networks as light-sensitive synapses or optically tunable memories. a) Corresponding

Submicron-sized mesas of resonant tunneling diodes (RTDs) with split drain contacts have been realized and the current-voltage characteristics have been studied in the bistable regime at room temperature. Dynamically biased, the RTDs show noise-triggered firing of spikelike signals and can act as reconfigurable universal logic gates for small voltage changes of a few millivolt at the input branches. These observations are interpreted in terms of a stochastic nonlinear processes. The logic gate operation shows gain for the fired-signal bursts with transconductance slopes exceeding the thermal limit. The RTD junction can be easily integrated to arrays of multiple inputs and have thus the potential to mimic neurons in nanoelectronic circuits.