We report on conductance measurements in carbon nanotube based double quantum dots connected to two normal electrodes and a central superconducting finger. By operating our devices as beam splitters, we provide evidence for crossed Andreev reflections tunable in situ. This opens an avenue to more sophisticated quantum opticslike experiments with spin entangled electrons.

https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.104.026801

Carbon nanotubes as Cooper pair beam splitters

In this study, a detailed investigation of the nonlinear optical properties of a spherical quantum dot (QD) containing one and two electrons has been carried out. First, intersublevel linear, third-order, and total absorptions of both single- and double-electron QDs have been investigated for cases with (i.e., D0 and D− donor) and without impurity. Second, linear, third-order, and total refractive indices have been examined in the same structure. In the calculation of optical properties, for the density of electrons in the QD considered, some symbolic values chosen are not similar to those in previous studies. The full numeric matrix diagonalization technique has been employed in determining sublevel energy eigenvalues and their wave functions. The Poisson–Schrodinger equations have been solved self-consistently in the Hartree approximation. In addition, the quantum mechanical many-body effects have been taken into account in local density approximation. The results are presented as a function of QD radii...

Third-order nonlinear optical properties of a one- and two-electron spherical quantum dot with and without a hydrogenic impurity

We analyze various limits of vibrationally coupled resonant electron transport in single-molecule junctions. Based on a master equation approach, we discuss analytic and numerical results for junctions under a high bias voltage or weak electronic-vibrational coupling. It is shown that in these limits, the vibrational excitation of the molecular bridge increases indefinitely, i.e., the junction exhibits a vibrational instability. Moreover, our analysis provides analytic results for the vibrational distribution function and reveals that these vibrational instabilities are related to electron-hole pair creation processes.

Vibrational instabilities in resonant electron transport through single-molecule junctions

The real-time, personalized and highly sensitive early-stage diagnosis of disease remains an important challenge in modern medicine. With the ability to interact with matter at the nanoscale, the development of nanotechnology architectures and materials could potentially extend subcellular and molecular detection beyond the limits of conventional diagnostic modalities. At the very least, nanotechnology should be able to dramatically accelerate biomarker discovery, as well as facilitate disease monitoring, especially of maladies presenting a high degree of molecular and compositional heterogeneity. This article gives an overview of several of the most promising nanodevices and nanomaterials along with their applications in clinical practice. Significant work to adapt nanoscale materials and devices to clinical applications involving large interdisciplinary collaborations is already underway with the potential for nanotechnology to become an important enabling diagnostic technology.

/pdf/nanodevices-in-diagnostics-1tmhjqsiga.pdf

Nanodevices in diagnostics.

Modern techniques of lithography make it possible to confine electrons to sufficiently small dimensions that the quantization of both their charge and their energy are easily observable. When such confined electrons are allowed to tunnel to metallicle ads a single electron transistor (SET) is created. This transistor turns on and off again every time one electron is added to the isolated region. Whereas we can understand conventional transistors using classical concepts, the SET is quantum mechanical in an essential way. In fact, there is a close analogy between the confined electrons inside an SET and an atom. In this review, the physics underlying the operation of SETs is explained, a brief history of its invention is presented, and issues of current interest are discussed. A conventional field-effect transistor, the kind that makes all modern electronics work, is a switch that turns on when electrons are added to a semiconductor and turns off when they are removed. These on and off states give the ones and zeros that digital computers need for calculation. Interestingly, these transistors are almost completely classical in their physics. Only a few numbers that characterize their behaviour are affected by quantum mechanics. However, if one makes a new kind of transistor, in which the electrons are confined within a small volume and communicate with the electrical leads by tunnelling, all this changes. One then has a transistor that turns on and off again every time one electron is added to it; we call it a single electron transistor (SET). Furthermore, the behaviour of the device is entirely quantum mechanical.

http://ijiet.com/wp-content/uploads/2013/02/63.pdf

Single Electron Transistor

Modern techniques of lithography make it possible to confine electrons to sufficiently small dimensions that the quantization of both their charge and their energy are easily observable. When such confined electrons are allowed to tunnel to metallic leads a single electron transistor (SET) is created. This transistor turns on and off again every time one electron is added to the isolated region. Whereas we can understand conventional transistors using classical concepts, the SET is quantum mechanical in an essential way. In fact, there is a close analogy between the confined electrons inside an SET and an atom. In this review, the physics underlying the operation of SETs is explained, a brief history of its invention is presented, and issues of current interest are discussed.

M.A. Kastner

Papers

The single electron transistor and artificial atoms