Random quantum states: recent developments and applications

We review the methods and use of random quantum states with particular emphasis on recent theoretical developments and applications in various fields. The guiding principle of the review is the idea that random quantum states can be understood as classical probability distributions in the Hilbert space of the associated quantum system. We show how this central concept connects questions of physical interest that cover different fields such as quantum statistical physics, quantum chaos, mesoscopic systems of both non-interacting and interacting particles, including superconducting and spin–orbit phenomena, and stochastic Schrödinger equations describing open quantum systems.     

纳米La_(0.67)Sr_(0.33)MnO_3块体的磁性与电输运特性研究

采用溶胶–凝胶法制备了纳米La0.67Sr0.33MnO3样品,通过XRD、TEM及PPMS(物理性质测量系统)研究了样品的结构、磁性和电输运特性。结果表明,样品为单相菱方钙钛矿结构,平均晶粒大小为61 nm,在10 K到300 K间样品具有铁磁性和绝缘体导电行为,在温度小于60 K时因库仑阻塞效应样品电阻随温度降低急遽增加。纳米晶粒尺寸导致样品具有强的磁电阻效应,其中低场磁电阻效应由晶粒间自旋极化电子隧穿界面引起,高场磁电阻效应由界面磁无序引起。     

集成化单电子器件研究进展

传统MOSFET结构正以较快的发展速度接近其物理极限,而单电子器件将成为新型的高性能集成化器件结构。本文采用量子点及其库伦阻塞效应等概念对单电子器件的工作原理进行了系统分析,并介绍了单电子器件在存储器和高灵敏度静电计方面的应用,最后指出了单电子器件的新发展方向及所面临的问题。     

Single-electron tunneling and Coulomb blockade in carbon-based quantum dots

Single-electron tunneling (SET) and Coulomb blockade (CB) phenomena have been widely observed in nanoscaled electronics and have received intense attention around the world. In the past few years, we have studied SET in carbon nanotube fragments and fullerenes by applying the so-called “Orthodox” theory [28]. As outlined in this review article, we investigated the single-electron charging and discharging process via current-voltage characteristics, gate effect, and electronic structure-related factors. Because the investigated geometric structures are three-dimensionally confined, resulting in a discrete spectrum of energy levels resembling the property of quantum dots, we evidenced the CB and Coulomb staircases in these structures. These nanostructures are sufficiently small that introducing even a single electron is sufficient to dramatically change the transport properties as a result of the charging energy associated with this extra electron. We found that the Coulomb staircases occur in the I–V characteristics only when the width of the left barrier junction is smaller than that of the right barrier junction. In this case, the transmission coefficient of the emitter junction is larger than that of the collector junction; also, occupied levels enter the bias window, thereby enhancing the tunneling extensively.      

Preparation of size controllable copper nanocrystals for nonvolatile memory applications

A method of fabricating Cu nanocrystals embedded in SiO2 dielectric film for nonvolatile memory applications by magnetron sputtering is introduced in this paper. The average size and distribution density of Cu nanocrystal grains are controlled by adjusting experimental parameters. The relationship between nanocrystal floating gate micro-structure and its charge storage capability is also discussed theoretically.     

Resistively coupled single-electron transistor using tunnel gate resistor

A resistively coupled single-electron transistor (R-SET) was fabricated using a modulation-doped heterostructure and metal Schottky gates, and measured at low temperature. Currents of R-SET with tunnel gate resistor were calculated using the orthodox theory. It is shown that the R-SET with tunnel gate resistor has quite similar properties to the originally proposed R-SET.     

Single FIR-photon detection using a quantum dot

We study single-electron-transistor (SET) operation of the quantum dot (QD) in a strong magnetic field under weak illumination of far-infrared (FIR) radiation, which causes cyclotron resonance (CR) excitation inside the QD. We find that the SET conductance resonance is exceedingly sensitive to the FIR: It switches on (off) upon the excitation of just one electron to a higher Landau level inside the QD, whereby enabling us to detect individual events of FIR-photon (hν 6 meV) absorption.     

电容耦合互初型单电子晶体管逻辑单元的数值模拟

根据单电子系统半经典模型,采用蒙特卡罗法单电子模拟程序对电容耦合的类ＣＭＯＳ单电子逻辑单元在不同参数条件下转移特性进行数值模拟,这种模拟器的物理内涵是通过建立ｎ沟单电子晶体管（ＳＥＴ）开关单元、ｑ沟ＳＥＴ开关单元以及互补型ＳＥＴ开关单元的电容电压荷方程,然后根据隧道前后系统自由能的变化来确定系统的隧穿率,建立电流－电压方程来决定开关特性而得到的。     

MAPK‐Targeted Drug Delivered by a pH‐Sensitive MSNP Nanocarrier Synergizes with PD‐1 Blockade in Melanoma without T‐Cell Suppression

The combination of BRAF/MEK‐targeted therapy with immune checkpoint blockade is regarded as a promising regimen for patients with metastatic melanoma due to their complementary advantages. However, MEK‐inhibitor‐induced T‐cell toxicity impedes effective cooperation. In this experiment, a pH‐responsive on‐demand controlled release mesoporous silica nanoparticles (MSNPs) system is designed. Fluorescein‐isothiocyanate‐loaded MSNP can be specifically delivered into tumor cells rather than T‐cells. MEK‐inhibitor‐loaded MSNP avoids proliferative and functional inhibitions of T‐cells, while preserving growth suppression of tumor cells in vitro. In an in vivo model, MSNP encapsulation reverses the MEK‐inhibitor‐induced suppression of activated CD8⁺ T‐cells, and enhances the secretion of INF‐γ and IL‐2. The combination of BRAF inhibitor plus MSNP‐loaded MEK inhibitor and anti‐PD‐1 antibody synergistically inhibits tumor growth via promoting robust immune‐related antitumor response. This work provides a novel and generalized framework for combining T‐cell‐impaired targeted therapy and immune checkpoint blockade by using a nanoparticle‐based delivery system.     

单电子晶体管通断图及其分析

通过研究单电子晶体管在电路中的静电能量的变化,得到了它的阻塞、导通情况与其两端偏压和控制栅压之间的关系,从而给出了它的通断图.并且发现单电子晶体管的对外特性主要由其对外的总电容决定;而单电子岛两个隧道结电容的不同主要反映在通断图上由隧道结电容所决定的晶体管阻塞、导通边界线上,这两条边界线同时也与外电路有关 关键词： 单电子晶体管 库仑阻塞 隧穿