介观物理系统的统计物理和持续电流

本文讨论介观系统的统计物理一些基本概念 ,在一般教科书和文献都很少有解释到的。我们讨论自平均效应 ,它在介观与宏观系统之不同 ,对杂质作系统平均后热力学量在介观与宏观系之不同。我们较详细引介用格林函数和图解法计算介观持续电流。同样 ,我们强调宏观系统和介观系统不同之处 ,对介观物理系统从计算热力学量的角度来看需要特别考虑因素。     

介观体系的物理

从对无序电子系统低温输运性质－弱局域电性的讨论出发，介绍了弹性散射和非弹发型用射的基本区别，引进了介观体系的概念，特别强调了与宏观体系不同之处，简单讲述了主要的物理发现，最后对本领域的现状做了简短的评述。     

介观系统的量子力学及统计物理特征

 介观体系是指介于宏观与微观之间的一类体系。介观体系的线度L满足aL≤Lφ的条件,其中a为原子半径,Lφ是介观体系的载流子保持相位记忆的特征长度,被称为退相位长度,因此介观体系中的载流子始终是相位关联的。退相位长度Lφ由体系的温度和物性共同决定,例如在液氦温度下,正常金属的Lφ可以达到μm量级,因此低温下介观系统的线度几乎是宏观的。介观系统的可观测的物理量仍然定义为大量微观粒子物理量的统计平均,与宏观系统的定义无异,微观粒子的运动遵循量子力学规律。对介观系统的研究始于20世纪80年代,现已成为凝聚态物理中一个令人瞩目的领域。     

介观物理系统的量子场论模型一维持续电流的Luttinger模型

本文以研究生进入选题前水平介绍介观物理系统中的一种重要的量子场论模型和方法。讨论一维介观电子系统的Luttinger模型和非费米液体的特征和基本物理。我们简单介绍重整化群概念和玻色化技术和用于一维Luttinger模型。     

介观体系和介场物理

20世纪 80年代初中期开始兴起的介观物理是凝聚态物理中人们十分关注的研究领域 ,“介观”一词大家已听得很多了 .一段时间以来 ,常读到介观尺度是由电子非弹性散射平均自由程决定的说法 ,觉得不太确切 .想到这一说法可能和我早先发表在《物理》杂志的文章[1] ,以及我们主编的《介观物理》一书第一版的前言[2 ] 有关 ,特写此短文说明 .这里的说明也许仍有不妥之处 ,请读者指正 .1　介观尺度介观体系的大小是由介观尺度来刻划的 .介观尺度是载流子保持相位记忆的长度 ,一般记为Ｌφ,称为退相位长度 .相位记忆的丢失源于载流子的非弹性散射 ,…     

电子相位相干时间

本期《物理双月刊》的“介观物理”专集中，马中水教授的《介观物理基础和近期发展几个方面的简单介绍》是一篇力作．该文对介观系统、介观物理的基础概念、介观物理发展的来龙去脉，以及近几年来介观物理领域因结合纳米科技而发展出来的新课题，做了非常全面性的介绍．这篇文章值得想要进入介观物理领域的研究生、博士后研究，以及已经在该领域从事某些课题研究的学者，仔细研读．马教授的文章，集中于讨论介观体系的（低温量子）电子传输性质．     

介观物理系统中的噪声

描述了介观物理系统中噪声的研究现况. 对热噪声和散粒噪声的物理起源做了详细介绍，热噪声是系统的能态占据数发生涨落引起的，而散粒噪声源于载流子传输的微粒特性. 还介绍了研究噪声的主要理论——散射理论，并给出了其在马鞍形半导体量子线和铁磁/绝缘体/半导体双异质结两种介观系统中的应用，指出了噪声研究的实际物理意义. 关键词： 介观物理 热噪声 散粒噪声 散射理论     

《介观物理》一书评介

介观系统的尺度一般在纳米到微米之间．今天的实验室已可制造介观样品．介观样品既类似宏观系统（例如包含数量巨大的粒子，物理量可按宏观那样定义和测量），又类似于微观系统（例如量子力学起决定作用，特别是波函数的相位起重要作用）．介观系统展示出许多奇特的与量子干涉有关的性质，引起物理学家的广泛兴趣．由于传统电子元件已日益接近工作原理的极限，以及量子干涉元件可能导致电子技术新革命，必将使已习惯于运用欧姆定律的电子工程师产生危机感．当前，即使不涉足凝聚态物理研究物理工作者，都对这一前途不可估量的新领域产生兴趣…     

介观物理基础和近期发展几个方面的简单介绍

低维和介观物理系统的研究是当前凝聚态理论的一个重要方向.文章将从回顾介观物理中的几个基本概念开始,就近年来在量子点、二维电子气和介观物理系统中的电子关联效应等几个方面的研究,简略地介绍介观物理的新发展和机遇.     

介观物理系统的量子场论模型一维持续电流的Luttinger模型

本文以研究生进入选题前水平介绍介观物理系统中的一种重要的量子场论模型和方法。讨论一维介观电子系统的Luttinger模型和非费米液体的特征和基本物理。我们简单介绍重整化群概念和玻色化技术和用于一维Luttinger模型。     

介观金属双环系统中的持续电流和量子能谱

基于电荷的不连续性,对处于外磁场中的介观双环系统进行量子化.假设系统在电荷表象中具有变换的对称性,通过求解电流和Hamilton算符的本征值方程,给出介观金属环互感系统中的量子电流和能谱关系;分析和研究了介观金属环中量子电流和能谱的性质.结果表明,持续电流和量子能谱不仅与外磁场、介观双环参数有关,而且还明显地依赖于电荷的量子化性质.     

有源介观LC电路的量子涨落

本文利用含时微扰论,研究了电源幅值较小时介观LC电路中电荷与电流的量子涨落。在确定的温度下,系统将处在混合态,进一步得到有限温度下含源介观LC电路的量子涨落。研究表明有源介观LC电路的量子涨落不仅与电路参数有关,还与时间和温度有关。     

Shapiro effect in mesoscopic LC circuit

In this paper we consider the movement of an electron in the single electron tunnel process through a mesoscopic capacitor. The results show that, due to the Coulomb force, there is a threshold voltage V_t in the mesoscopic LC circuit. When the external voltage is lower than the threshold voltage, the tunnel current value is zero, and the Coulomb blockade phenomenon arises. Furthermore, considering that the mesoscopic dimension is comparable to the coherence length in which charge carriers retain the phase remembrance, a weak coupling can be produced through the proximity effect of the normal metal electrons of both electrodes of a mesoscopic capacitor. By varying the external voltage, we can observe the Shapiro current step on the current－voltage characteristic curve of a mesoscopic LC circuit.     

Time dependence of the average charge and current in a dissipative mesoscopic circuit

Taking into consideration the interactions between electrons and phonons,we have studied the temporal evolution of the average charge and current in a dissipative mesoscopic RLC circuit.Our results show that a mesoscopic RLC circuit can be treated as an interactive system between an electromagnetic harmonic oscillator and many lattice harmonic oscillators;this is called the bathing of the harmonic oscillators.The results also show that the quantum equation of motion of the linear mesoscopic RLC circuit is identical in form to its classical equation of motion,the only difference between them being their respective meanings.In order to thoroughly study the quantum properties of a dissipative mesoscopic circuit,we have to consider not only the electromagnetic energy of the circuit,but also the crystal lattice vibration energy and the interactive energy between electrons and phonons.     

Photocurrent, rectification, and magnetic field symmetry of induced current through quantum dots

We report mesoscopic dc current generation in an open chaotic quantum dot with ac excitation applied to one of the shape-defining gates. For excitation frequencies large compared to the inverse dwell time of electrons in the dot (i.e., GHz), we find mesoscopic fluctuations of induced current that are fully asymmetric in the applied perpendicular magnetic field, as predicted by recent theory. Conductance, measured simultaneously, is found to be symmetric in field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is always symmetric in field, suggesting its origin is mesoscopic rectification.     

Dynamic conductance of a ballistic quantum wire

Within the framework of exact linear response theory, we derive a general formula, with which the dynamic conductance of mesoscopic system can be determined in the absence of Coulomb interaction. In addition, we present a solution to the problem of current partition in the system. These allow the derivation of dynamic conductance in time-dependent case. As a natural consequence, the current (charge) conservation and gauge invariance conditions are fulfilled. To give an example, we discuss the dynamic conductance of a ballistic quantum wire, and the effect of contacts on the conductance is also discussed.     

Quantum Effect in the Mesoscopic RLC Circuits with a Source

The research work on the quantum effects in mesoscopic circuits has undergone a rapid development recently, however the whole quantum theory of the mesoscopic circuits should consider the discreteness of the electric charge. In this paper, based on the fundamental fact that the electric charge takes discrete values, the finite-difference Schrodinger equation of.the mesoscopic RLC circuit with a source is achieved. With a unitary transformation, the Schrodinger equation becomes the standard Mathieu equation, then the energy spectrum and the wave functions of the system are obtained. Using the WKBJ method, the average of currents and square of the current are calculated. The results show the existence of the current fluctuation, which causes noise in the circuits. This paper is an application of the whole quantum mesoscopic circuits theory to the fundamental circuits, and the results will shed light on the design of the miniation circuits, especially on the purpose of reducing quantum noise coherent controlling of the mesoscopic quantum states.     

Quantum Effect in the Mesoscopic RLC Circuits with a Source

The research work on the quantum effects in mesoscopic circuits has undergone a rapid development recently, however the whole quantum theory of the mesoscopic circuits should consider the discreteness of the electric charge. In this paper, based on the fundamental fact that the electric charge takes discrete values, the finite-difference Schrodinger equation of the mesoscopic RLC circuit with a source is achieved. With a unitary transformation, the Schrodinger equation becomes the standard Mathieu equation, then the energy spectrum and the wave functions of the system are obtained. Using the WKBJ method, the average of durrents and square of the current are calculated. The results show the existence of the current fluctuation, which causes noise in the circuits. This paper is an application of the whole quantum mesoscopic circuits theory to the fundamental circuits, and the results will shed light on the design of the miniation circuits, especially on the purpose of reducing quantum noise coherent controlling of the mesoscopic quantum states.     

三臂环中的持续电流

利用量子波导理论研究三臂环中的持续电流.结果表明,输运电流存在时,不含磁场且上、下臂等长的三臂环中仍可以有持续电流出现,而且上臂和下臂中的持续电流是相同的.三臂环的各臂长不等时,三个臂中的持续电流各不相同.我们还发现,即使三臂环和单环的上、下臂比值一样,两个环中的持续电流也明显不同.