Ian Affleck, University of British Columbia
Title: The Kondo effect in quantum dots and in atoms on surfaces

A spin-1/2 impurity in a metal or a quantum dot on a semi-conductor interface can lead to some simple but interesting many body physics in which the impurity spin acts freely at T >> T_K but forms a spin singlet with a conduction electron at T<<T_K where T_K is called the Kondo temperature.

In these lectures I will:

1. Review the renormalization group picture and phenomenology of the Kondo
   effect in metals
2. Discuss the Kondo effect in quantum dots
3. Introduce non-Fermi liquid Kondo effects seen in double quantum dots

Maxwell invented his famous demon to illustrate the subtleties of the second law of thermodynamics and his conjecture has inspired much discussion ever since. Technology has now reached a point where it is possible to build an electronic Maxwell’s demon that can be interposed between the two contacts (source and drain) of a nanoscale conductor (the channel) to allow electrons to flow preferentially in one direction so that a current will flow in the external circuit even without any external source of power.

 In this series of three talks I will use this device to illustrate the fundamental role of “contacts” and “demons” in transport and energy conversion. The discussion is kept at an academic level steering clear of real world details, but the illustrative devices we use are very much within the capabilities of present-day technology. Indeed the Maxwell’s demon device itself is very similar to the pentalayer spin-torque device which has been studied by a number of groups though we are not aware of any attempt to use it as a nanoscale heat engine or as a refrigerator as proposed here.

The objective, however, is not to evaluate possible practical applications. Rather it is to introduce a transparent model for quantum transport far from equilibrium based on a combination of the Landauer approach with the non-equilibrium Green function (NEGF) method, which is now being widely used in the analysis and design of nanoscale devices. It provides a unified description for all kinds of devices from molecular conductors to carbon nanotubes to silicon transistors covering different transport regimes from the ballistic to the diffusive limit. But most importantly, it leads to a unique view of current flow that is very different from the conventional viewpoint.

References:

1. S.Datta, Nanodevices and Maxwell’s demon, to appear in the Proceedings of the Third ASI International Workshop on Nano Science & Technology, Ed. Z.K. Tang, Taylor & Francis (2007), arXiv:cond-mat/0704.1623.
2. S.Datta, Concepts of Quantum Transport, a series of video lectures, http://www.nanohub.org/courses/cqt.
3. S.Datta, Quantum Transport: Atom to Transistor, Cambridge (2005).
   

The first demonstration of electron spin detection in solid state materials came with the advent of electron spin resonance in the 1940's. Electron spin resonance (ESR) is an ensemble measurement, sensitive to the minute magnetic moment of an electron spin only when integrated over 10^9 or more electrons. Over the past 5 years, a variety of experimental techniques have been developed that push the detection limit down to the single electron level. These efforts have been motivated in part by aspirations of quantum information processing, and in part by a more fundamental interest in spin decoherence mechanisms and interactions with the spin degree of freedom in a solid state material. This series of seminars will present an overview of these developments, their motivations, and an outlook for the future.

Hong Guo, Center for the Physics of Materials and Department of Physics, University McGill
Title: Computational Nano-Electronics

One of the most important branches of nanotechnology research is the nanoelectronics. Nanoelectronic devices operate by the principle of quantum mechanics and device properties are closely related to the atomic structure of the system. It has been a theoretical challenge to calculate device characteristics including relevant microscopic details of the device structure in the nonequilibrium and quantum regime.

In these lectures, I will review the present status of nanoelectronic device theory, the existing theoretical and numerical challenges, and some important problems of nanoelectronics. I will then introduce and discuss various approaches for calculating quantum transport properties of coherent quantum structures. This discussion leads to the introduction of a formalism where density functional theory (DFT) is carried out within the Keldysh nonequilibrium Green's function (NEGF) framework. We demonstrate that the NEGF-DFT formalism allows quantitative calculations of nonlinear and nonequilibrium charge and spin transport properties of various nanoscale conductors without involving any phenomenological parameter. The detailed theoretical background of the NEGF-DFT formalism as well as its numerical implementation will be presented. Quantitative comparisons to measured data on various nanoelectronic devices will be made. I will then go through examples of quantum transport through nanoscale devices based on the NEGF-DFT analysis: resistance of atomic and molecular wires, nano-scale spintronics, field effects, STM image simluations, molecular vibrational spectrum during current flow, non-equilibrium electron-phonon coupling strength, inelastic current, MRAM modeling, current induced magnetic moment reversal, graphene electronics and various ideas of novel quantum devices.

The NEGF-DFT formalism is most conveniently carried out for device simulations in the steady-state within a mean field manner. Extensions and improvements are necessary for situations of transient transport and strong correlation. I will discuss some efforts in these directions and provide a outlook on computational nanoelectronics.

Student Posters

Full counting statistics in nanoelectromechanical systems

Dewetting in molecule on insulator systems: two prototypical examples

Nanoscale Hall probes: fabrication of magnetic sensors

Spin Properties of the lateral triple quantum dot molecule in the presence of a magnetic field

Controlled deposition of metal wires and contacts on KBr using nanostencils and surface structures

Nonlocal spin and charge effects in two-dimensional electron gas nanostructures

Simultaneous STM/AFM measurements with defined tips - understanding interactions at the atomic scale

Dephasing effect in ab initio modeling of a benzene molecule with aluminium leads

Two- and Three- Energy Level Mixing Effects in Vertically Coupled Quantum Dots

Coherent Transport in Triple Quantum Dots

Calculations of Electron Transport through Substituted Benzenes

New Lithography methods for fabricating structures of micro and nanoelectronics