Quantum Nature of the Nanoworld

The particles of matter (electrons, protons, neutrons) provide limits to the smallness of anything composed of chemical matter, which is itself composed of atoms. The rules that these particles obey are different from the rules of macroscopic matter. An understanding of the rules is useful to understand the structure of atoms and chemical matter. An understanding of these rules, and of the relation between the wave and particle natures of light, is also key to understanding deviations from...

Quantum Technologies Based on Magnetism Electron and Nuclear Spin and Superconductivity 173

8.1 The Stern-Gerlach Experiment Observation of Spin V2 Angular Momentum of the Electron 176 8.2 Two Nuclear Spin Effects MRI (Magnetic Resonance Imaging) and the 21.1 cm Line 177 8.3 Electron Spin V2 as a Qubit for a Quantum Computer Quantum Superposition, Coherence 180 8.4 Hard and Soft Ferromagnets 183 8.5 The Origins of GMR (Giant Magnetoresistance) Spin-dependent Scattering of Electrons 184 8.6 The GMR Spin Valve, a Nanophysical Magnetoresistance Sensor 186 8.7 The Tunnel Valve, a Better...

Linear Engines on Tracks

The spring and ratchet systems, structurally ill-defined but clearly electrostatic in mechanism, contrast with well defined linear and rotary engines, which move in stepwise fashions, however, with mechanisms that remain unclear. In this discussion we mention the linear motors myosin and kinesin 8 and an example of a rotary motor, suitable for driving a flagellum, in this case F1-adenosine triphosphate synthase. In contrast to the spring systems, the energetics of these linear and rotary motors...

Josephson Effect and the Superconducting Quantum Interference Detector SQUID

The superconducting wavefunction has a reliable phase, 0, which applies to a macroscopic number of electrons. This regularity is enforced by the pairing phenomenon, which leads to a macroscopic number of pairs of electrons in precisely the same quantum state, analogous to the macroscopic number of photons occupying a single electromagnetic mode in a laser. (The phenomenon is also similar to a single ferromagnetic domain, where all electron spins are parallel.) The reliability of the...

Ion Channels the Nanotransistors of Biology

The smallest forms of life are bacteria, which are single cells of micrometer size. Cells are enclosed by an impermeable lipid bilayer membrane, the cell wall. This hydrophobic layer is akin to a soap bubble. Lipid cell walls are ubiquitous in all forms of life. Communication from the cell to the extracellular environment is accomplished in part by ion channels, which allow specific ion species to enter or leave the cell. Two specific types of transmembrane protein ion channels are the Ca++...

The Degenerate Semiconductor

Now consider an extreme case, which will lead to an understanding of a heavily doped, metallic semiconductor, as is typical of the important 2DEG electron gas. Consider pure InAs, for which data in Table 5.2 indicate a bandgap of 0.33 eV, electron mass 0.02, hole mass 0.41 and dielectric constant 14.5. First we estimate Ne at 300 K, assuming for simplicity that the Fermi energy is exactly at the center of the energy gap. We find Ne 2(2pme*kBT h2)3 2 exp -(EG-EF) fcBT 7.165 x 1022 x 1.7 x 10-3...

Piezoelectric Materials

A piezoelectric material can be characterized, e.g., by the fractional change in its x-dimension per unit electric field in the z-direction. As an example, for the useful and commercially available (polycrystalline) material known as PZT-5H, a quoted value of the coefficient D31 S1 E3 strain in 1-direction electric field in 3-direc-tion -2.74 A V. Here the acronym PZTrefers to Strain is a fractional distortion, so that for a bar of length x L, the strain, DL L, is calculated as D31V't, if the...

Spin Injection the Johnson Silsbee Effect

Johnson and Silsbee 13 demonstrated experimentally that a non-equilibrium density of spin-polarized electrons can be transferred from a ferromagnet into a nonmagnetic metal, like aluminum, under proper conditions. An important corollary, demonstrated experimentally in their pioneering work, is that the same type of fer-romagnet-insulator-normal metal junction responds to the presence of non-equilib- Figure 8.10 Geometry of the spin injection device 14 . (a) SEM image of device with spacing L of...

What is the Future of Silicon Computer Technology

The ongoing improvement of silicon computer chips continues, with innovative new device designs appearing frequently. In addition to the International Technology Roadmap for Silicon 1 , a further analysis of the trends is given by Meindl et al. 6 . One of the recent trends has been to build the basic field effect transistor, FET, or MOSFET Metal Oxide Silicon Field Effect Transistor , on a silicon chip with a buried oxide layer BOX . The effect of the BOX is intended to reduce the thickness of...

C60 Buckyball 05 nm

These molecules are empty spherical shells, containing exactly 60 carbon atoms in five- and six-membered rings. It is essentially a graphene sheet closed onto itself, with pentagons added to allow curvature. The pentagonal and hexagonal benzene rings are located in a similar fashion to pentagonal and hexagonal panels in a soccer ball. These molecules are very stable and fully tie up the four valence electrons of each carbon atom. A simple model of this molecule is shown in Figure 6.2 2 . Figure...

Ethylene C2H4 Benzene C6H6 and Acetylene C2H2

The carbon molecules considered so far have involved only single bonds, based simply on the covalent bonding found in molecular hydrogen that was discussed in Chapter 5, acting on wavefunctions as listed in Table 4.1. Carbon and other atoms also sometimes form double and triple covalent bonds. The linear acetylene molecule C2H2 is formed by carbon atoms which each share three of their four valence electrons with each other, a structure called a triple bond. Thus, six valence electrons are...

Scaling the xylophone

The familiar xylophone produces musical sounds when its keys a linear array of rectangular bars of dimensions a x b x c, with progressively longer key lengths c producing lower audio frequencies are struck by a mallet and go into transverse vibration perpendicular to the smallest, a, dimension. The traditional middle C in music corresponds to 256 Hz. If the size scale of the xylophone key is reduced to the micrometer scale, as has recently been achieved, using the semiconductor technology, and...