Inter-dot coupling effects on transport through correlated parallel coupled quantum dots

Transport through symmetric parallel coupled quantum dot system has been studied, using non-equilibrium Green function formalism. The inter-dot tunnelling with on-dot and inter-dot Coulomb repulsion is included. The transmission coefficient and Landaur-Buttiker like current formula are shown in terms of internal states of quantum dots. The effect of inter-dot tunnelling on transport properties has been explored. Results, in intermediate inter-dot coupling regime show signatures of merger of two dots to form a single composite dot and in strong coupling regime the behaviour of the system resembles the two decoupled dots.      

基于非线性受控电压源的单电子晶体管宏模型

提出了一种新颖的基于非线性受控电压源的单电子晶体管宏模型.该宏模型通过受栅压和温度控制的非线性受控电压源使温度效应和栅控效应的模拟更加方便,并提高了单电子晶体管特性的模拟精度.此外,该宏模型结构简单,可以利用极小的计算机资源得到与传统的蒙特卡罗方法基本一致的模拟结果,并可方便地嵌入SPICE中进行一定规模的单电子晶体管电路的模拟     

纳米级SET/CMOS混合器件的研究进展

SET/CMOS作为一种单电子晶体管与纳米级CMOS混合结构的新兴纳米电子器件,不仅实现两者优势互补,而且其突出的功能特性极大影响着电路微型化发展的道路。从SET/CMOS的串联和并联两种基本结构出发,阐述了各自的工作原理与特性、进而介绍了该混合器件目前在实验室制备、电路设计以及数值模拟研究方面的现状,最后讨论了器件在发展中尚需解决的问题及其应用前景。SET/CMOS的容错电路及互连结构新型设计将会加速实用化的进程,使集成电路产生质的飞跃,进而有望实现超高密度的信息存储和超高速信息处理,并将在未来智能计算机、通信设备和自动化方面发挥重要作用。     

Effect of Coulomb blockade on the switching time of Ag–Ag2S–Pt atomic switches

A theoretical model based on the single electron tunneling phenomenon is employed to calculate the time-dependent electrical resistance of an Ag–Ag₂S–Pt atomic switch at different applied voltages. While a negative voltage is applied to Pt electrode, Ag atoms precipitate on the surface of Ag₂S electrode where they form Ag clusters. The resistance of switch decreases as Ag clusters grow larger between two electrodes. Our model calculations imply the time required to decrease the resistance of switch below the resistance quantum (switching time) is mainly determined by the Coulomb blockade effect of Ag clusters. The switching time is found to decrease exponentially with increasing the applied voltage, which agrees very well with the experimental observations.     

Background charges and quantum effects in quantum dots transport spectroscopy

We extend a simple model of a charge trap coupled to a single-electron box to energy ranges and parameters such that it gives new insights and predictions readily observable in many experimental systems. We show that a single background charge is enough to give lines of differential conductance in the stability diagram of the quantum dot, even within undistorted Coulomb diamonds. It also suppresses the current near degeneracy of the impurity charge, and yields negative differential lines far from this degeneracy. We compare this picture to two other accepted explanations for lines in diamonds, based respectively on the excitation spectrum of a quantum dot and on fluctuations of the density-of-states in the contacts. In order to discriminate between these models, we emphasize the specific features related to environmental charge traps. Finally we show that our model accounts very well for all the anomalous features observed in silicon nanowire quantum dots.     

Fano effect in a double T-shaped interferometer

We study the coherent transport in a one-dimensional lead with two side-coupled quantum dots using the Keldysh’s Green function formalism.The effect of the interdot Coulomb interaction is taken into account by computing the firstand second order contributions to the self-energy.We show that the Fano interference due to the resonance of one dotis strongly affected by the fixed parameters that characterize the second dot. If the second dot is tuned close to resonance an additionalpeak develops between the peak and dip of the Fano line shape of the current. In contrast, when the second dotis off-resonance and its occupation number is close to unity the interdot Coulomb interaction merely shifts the Fano line and no other maxima appear.The system we consider is more general than the single-dot interferometer studied experimentally by Kobayashi et al. [Phys. Rev. B 70, 035319 (2004)] and may be used for controlling quantum interference and studying decoherence effects in mesoscopic transport.     

Quantum many‐body phenomena in coupled cavity arrays

The increasing level of experimental control over atomic and optical systems gained in recent years has paved the way for the exploration of new physical regimes in quantum optics and atomic physics, characterised by the appearance of quantum many‐body phenomena, originally encountered only in condensed‐matter physics, and the possibility of experimentally accessing them in a more controlled manner. In this review article we survey recent theoretical studies concerning the use of cavity quantum electrodynamics to create quantum many‐body systems. Based on recent experimental progress in the fabrication of arrays of interacting micro‐cavities and on their coupling to atomic‐like structures in several different physical architectures, we review proposals on the realisation of paradigmatic many‐body models in such systems, such as the Bose‐Hubbard and the anisotropic Heisenberg models. Such arrays of coupled cavities offer interesting properties as simulators of quantum many‐body physics, including the full addressability of individual sites and the accessibility of inhomogeneous models.     

Biphenyl Ether Analogs Containing Pomalidomide as Small-Molecule Inhibitors of the Programmed Cell Death-1/Programmed Cell Death-Ligand 1 Interaction

New biphenyl-based chimeric compounds containing pomalidomide were developed and evaluated for their activity to inhibit and degrade the programmed cell death-1/programmed cell death- ligand 1 (PD-1/PD-L1) complex. Most of the compounds displayed excellent inhibitory activity against PD-1/PD-L1, as assessed by the homogenous time-resolved fluorescence (HTRF) binding assay. Among them, compound 3 is one of the best with an IC₅₀ value of 60 nM. Using an ex vivo PD-1/PD-L1 blockade cell line bioassay that expresses human PD-1 and PD-L1, we show that compounds 4 and 5 significantly restore the repressed immunity in this co-culture model. Western blot data, however, demonstrated that these anti-PD-L1/pomalidomide chimeras could not reduce the protein levels of PD-L1.     

利用纳米孔研究DNA

脱氧核糖核酸 (DNA)和蛋白质是构成生命体最为重要的两类生物大分子 .随着科学技术的快速发展 ,越来越多的纳米技术被用来研究这些生物大分子 .文章详细介绍了近来利用纳米孔技术研究DNA的一些进展 .结合作者近期利用聚焦离子束 (FIB)制作纳米孔的工作 ,提出了利用纳米孔解离核小体的设想 .如果能够利用纳米孔将双螺旋DNA从组蛋白八聚体上剥离下来 ,并探测这一过程 ,将揭示核小体中包含的许多生物化学、物理信息 .文章对此进行了较为详细的分析 :处于电场中的核小体在电场的作用下 ,DNA分子穿越纳米孔 ,同时由于纳米孔的阻挡力 ,使组蛋白不能穿越 ,从而诱使DNA从组蛋白八聚体上分离下来 .通过准确检测DNA分子穿孔过程中引起的电流阻塞效应 ,可将DNA与组蛋白的相互作用的一些性质反映出来     

Evidence for Coulomb staircase in tunneling through an antidot island in the quantum Hall regime

We studied the – characteristics of tunneling devices, defined by two trench fingers and an antidot island patterned on Corbino rings in the quantum Hall plateau regime. Well-developed current steps were observed at filling factors near , which we interpret as a Coulomb staircase phenomenon due to charging of compressible strips around the antidot. The evolution of the current steps with filling factor is explained in the quasi-elastic inter landau level scattering model.