Towards spin injection from silicon into topological insulators: Schottky barrier between Si and Bi2Se3

A scheme is proposed to electrically measure the spin-momentum coupling in the topological insulator surface state by injection of spin polarized electrons from silicon. As a first approach, devices were fabricated consisting of thin (<100nm) exfoliated crystals of Bi2Se3 on n-type silicon with independent electrical contacts to silicon and Bi2Se3. Analysis of the temperature dependence of thermionic emission in reverse bias indicates a barrier height of 0.34 eV at the Si-Bi2Se3 interface. This robust Schottky barrier opens the possibility of novel device designs based on sub-band gap internal photoemission from Bi2Se3 into Si

Nonequilibrium Transport through a Kondo Dot in a Magnetic Field: Perturbation Theory

Using nonequilibrium perturbation theory, we investigate the nonlinear transport through a quantum dot in the Kondo regime in the presence of a magnetic field. We calculate the leading logarithmic corrections to the local magnetization and the differential conductance, which are characteristic of the Kondo effect out of equilibrium. By solving a quantum Boltzmann equation, we determine the nonequilibrium magnetization on the dot and show that the application of both a finite bias voltage and a magnetic field induces a novel structure of logarithmic corrections not present in equilibrium. These corrections lead to more pronounced features in the conductance, and their form calls for a modification of the perturbative renormalization group.Comment: 16 pages, 7 figure

Suppression of Kondo effect in a quantum dot by external irradiation

We demonstrate that the external irradiation brings decoherence in the spin states of the quantum dot. This effect cuts off the Kondo anomaly in conductance even at zero temperature. We evaluate the dependence of the DC conductance in the Kondo regime on the power of irradiation, this dependence being determined by the decoherence.Comment: 4 pages, 1 figur

Restorative Justice-Informed Moral Acquaintance: Resolving the Dual Role Problem in Correctional and Forensic Practice

The issue of dual roles within forensic and correctional fields has typically been conceptualized as dissonance—experienced by practitioners— when attempting to adhere to the conflicting ethical requirements associated with client well-being and community protection. In this paper, we argue that the dual role problem should be conceptualized more broadly; to incorporate the relationship between the offender and their victim. We also propose that Restorative Justice (RJ) is able to provide a preliminary ethical framework to deal with this common ethical oversight. Furthermore, we unite the RJ framework with that of Ward’s (2013) moral acquaintance model to provide a more powerful approach—RJ informed moral acquaintance—aimed at addressing the ethical challenges faced by practitioners within forensic and correctional roles

Empresas nanotecnológicas en México: hacia un primer inventario

En este artículo presentamos un inventario inicial de compañías mexicanas que venden productos que son manufacturados a partir de nanotecnología, o que utilizan nanotecnología en sus operaciones. El inventario permite a los interesados identificar el número de empresas, su ubicación geográfica y los sectores industriales en los que se insertan. Esto es, de hecho, un primer acercamiento para el análisis los vínculos productivos de la nanotecnología en México. Los resultados muestran una alta concentración de empresas en dos estados: Nuevo León y la ciudad de México. Esto sucede en un contexto donde no hay una iniciativa nacional, ni una política pública específica ni datos disponibles públicamente o bases de datos que contienen información relevante

The Kondo Effect in Non-Equilibrium Quantum Dots: Perturbative Renormalization Group

While the properties of the Kondo model in equilibrium are very well understood, much less is known for Kondo systems out of equilibrium. We study the properties of a quantum dot in the Kondo regime, when a large bias voltage V and/or a large magnetic field B is applied. Using the perturbative renormalization group generalized to stationary nonequilibrium situations, we calculate renormalized couplings, keeping their important energy dependence. We show that in a magnetic field the spin occupation of the quantum dot is non-thermal, being controlled by V and B in a complex way to be calculated by solving a quantum Boltzmann equation. We find that the well-known suppression of the Kondo effect at finite V>>T_K (Kondo temperature) is caused by inelastic dephasing processes induced by the current through the dot. We calculate the corresponding decoherence rate, which serves to cut off the RG flow usually well inside the perturbative regime (with possible exceptions). As a consequence, the differential conductance, the local magnetization, the spin relaxation rates and the local spectral function may be calculated for large V,B >> T_K in a controlled way.Comment: 9 pages, invited paper for a special edition of JPSJ "Kondo Effect -- 40 Years after the Discovery", some typos correcte

For China to realise its research and innovation potential the government may have to place greater trust in the academic community

After three decades of being the world's manufacturing powerhouse, China is now looking to science and technology to drive its economic future. However, a recent study suggests that China's higher education research environment faces numerous challenges that may hinder the country from realising its research and innovation potential; from the promotion of short-term thinking, to an excessive level of bureaucratic and governmental intervention. Xueying Han and Richard P. Appelbaum argue that for China to reach the next level of research and innovation, the central government may have to cede control and trust the academic community to take a more active role in guiding the country’s research direction

Transverse momentum nonconservation at the ErAs/GaAs interface

Because ErAs, a semimetal, grows epitaxially on GaAs(100), ErAs-base/ GaAs-collector metal-base transistors provide a uniquely simple system in which to study the interfacial transverse momentum conservation of hot electrons. This system is also of interest for metal-semiconductor superlattice thermal energy conversion devices that utilize ErAs as the interbarrier material. A key requirement for such devices to outperform bulk thermal energy converters is the nonconservation of transverse momentum. Our results, indicating total nonconservation of transverse momentum, could therefore lead to significantly more efficient thermal energy conversion devices