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Bloch Oscillations
Bloch oscillation is a phenomenon from solid state physics. It describes the oscillation of a particle (e.g. an electron) confined in a periodic potential when a constant force is acting on it. It was first pointed out by Felix Bloch and Clarence Zener while studying the electrical properties of crystals. In particular, they predicted that the motion of electrons in a perfect crystal under the action of a constant electric field would be oscillatory instead of uniform. While in natural crystals this phenomenon is extremely hard to observe due to the scattering of electrons by lattice defects, it has been observed in semiconductor superlattices and in different physical systems such as cold atoms in an optical potential and ultrasmall Josephson junctions. Derivation The one-dimensional equation of motion for an electron with wave vector k in a constant electric field E is: \frac = \hbar \frac = -eE, which has the solution k(t) = k(0) - \frac t. The group velocity v of the el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bloch Oscillations
Bloch oscillation is a phenomenon from solid state physics. It describes the oscillation of a particle (e.g. an electron) confined in a periodic potential when a constant force is acting on it. It was first pointed out by Felix Bloch and Clarence Zener while studying the electrical properties of crystals. In particular, they predicted that the motion of electrons in a perfect crystal under the action of a constant electric field would be oscillatory instead of uniform. While in natural crystals this phenomenon is extremely hard to observe due to the scattering of electrons by lattice defects, it has been observed in semiconductor superlattices and in different physical systems such as cold atoms in an optical potential and ultrasmall Josephson junctions. Derivation The one-dimensional equation of motion for an electron with wave vector k in a constant electric field E is: \frac = \hbar \frac = -eE, which has the solution k(t) = k(0) - \frac t. The group velocity v of the el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group Velocity
The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the ''modulation'' or ''envelope'' of the wave—propagates through space. For example, if a stone is thrown into the middle of a very still pond, a circular pattern of waves with a quiescent center appears in the water, also known as a capillary wave. The expanding ring of waves is the wave group, within which one can discern individual waves that travel faster than the group as a whole. The amplitudes of the individual waves grow as they emerge from the trailing edge of the group and diminish as they approach the leading edge of the group. Definition and interpretation Definition The group velocity is defined by the equation: :v_ \ \equiv\ \frac\, where is the wave's angular frequency (usually expressed in radians per second), and is the angular wavenumber (usually expressed in radians per meter). The phase velocity is: . The function , whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Super Bloch Oscillations
In physics, a Super Bloch oscillation describes a certain type of motion of a particle in a lattice potential under external periodic driving. The term super refers to the fact that the amplitude in position space of such an oscillation is several orders of magnitude larger than for 'normal' Bloch oscillations. Bloch oscillations vs. Super Bloch oscillations Normal Bloch oscillations and Super Bloch oscillations are closely connected. In general, Bloch oscillations are a consequence of the periodic structure of the lattice potential and the existence of a maximum value of the Bloch wave vector k_\text. A constant force F_0 results in the acceleration of the particle until the edge of the first Brillouin zone is reached. The following sudden change in velocity from +\hbar k_\text/m to -\hbar k_\text/m can be interpreted as a Bragg scattering of the particle by the lattice potential. As a result, the velocity of the particle never exceeds , \hbar k_\text/m, but oscillates in a saw-to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomas Dekorsy
Thomas may refer to: People * List of people with given name Thomas * Thomas (name) * Thomas (surname) * Saint Thomas (other) * Thomas Aquinas (1225–1274) Italian Dominican friar, philosopher, and Doctor of the Church * Thomas the Apostle * Thomas (bishop of the East Angles) (fl. 640s–650s), medieval Bishop of the East Angles * Thomas (Archdeacon of Barnstaple) (fl. 1203), Archdeacon of Barnstaple * Thomas, Count of Perche (1195–1217), Count of Perche * Thomas (bishop of Finland) (1248), first known Bishop of Finland * Thomas, Earl of Mar (1330–1377), 14th-century Earl, Aberdeen, Scotland Geography Places in the United States * Thomas, Illinois * Thomas, Indiana * Thomas, Oklahoma * Thomas, Oregon * Thomas, South Dakota * Thomas, Virginia * Thomas, Washington * Thomas, West Virginia * Thomas County (other) * Thomas Township (other) Elsewhere * Thomas Glacier (Greenland) Arts, entertainment, and media * ''Thomas'' (Burton novel) 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hartmut Roskos
Hartmut is a given name. Notable people with the name include: *Hartmut of Saint Gall (died 905), Benedictine abbot * Hartmut Bagger (born 1938), retired German general of the Bundeswehr * Hartmut Becker (born 1938), German actor * Hartmut Boockmann (1934–1998), German historian and researcher in medieval history * Hartmut Briesenick (born 1949), East German athlete, mainly men's shot put * Hartmut Büttner, German politician (German Christian Democratic Union) * Hartmut Elsenhans (born 1941), German political scientist, professor at the Universität Leipzig *Hartmut Erbse (1915–2004), German classical philologist *Hartmut Esslinger (born 1944), German-American industrial designer * Hartmut Fähndrich (born 1944), German-Arabic translator * Hartmut Faust (born 1965), West German sprint canoeist * Hartmut Fromm (born 1950), retired German football defender * Hartmut Geerken (born 1939), German musician, composer, writer, journalist, playwright, and filmmaker * Hartmut Gründler ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karl Leo
Karl Leo (born 10 July 1960 in Freiburg im Breisgau, Baden-Württemberg, Germany) is a German physicist. Career Leo studied physics at the Albert-Ludwigs-Universität Freiburg and obtained the Diplomphysiker degree with a thesis on solar cells under supervision of Adolf Goetzberger at the Fraunhofer-Institut für Solare Energiesysteme. In 1986 he joined the Max-Planck-Institut für Festkörperforschung in Stuttgart for a PhD under the guidance of Hans Queisser. He then joined AT&T Bell Laboratories in Holmdel (New Jersey) as a postdoctoral research associate. In 1991 he joined the RWTH Aachen as an assistant professor and obtained the Habilitation degree. In 1993 he joined the Technische Universitaet Dresden as a professor of optoelectronics. Since 2002 he has been also with the Fraunhofer-Institut für Photonische Mikrosysteme, currently as director. Achievements Leo works in the field of semiconductor optics and the physics of thin organic films. In 1992 he discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jochen Feldmann
Jochen is a given name. Notable people with the name include: *Jochen Asche, East German luger, competed during the 1960s *Jochen Böhler (born 1969), German historian, specializing in the history of World War II *Jochen Babock (born 1953), East German bobsledder * Jochen Bachfeld (born 1952), retired boxer from East Germany *Jochen Balke (1917–1944), German breaststroke swimmer * Jochen Behle (born 1960), former (West) German cross-country skier *Jochen Bleicken (1926–2005), German professor of ancient history * Jochen Borchert (born 1940), German politician and member of the CDU *Jochen Breiholz, German opera manager *Jochen Busse (born 1941), German television actor * Jochen Carow (born 1944), German former footballer * Jochen Cassel (born 1981), German badminton player *Jochen Danneberg (born 1953), East German ski jumper * Jochen Dornbusch, the coach for the men's Hong Kong national team * Jochen Endreß (born 1972), retired German football player * Jochen Förster (born 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy Band
In solid-state physics, the electronic band structure (or simply band structure) of a solid describes the range of energy levels that electrons may have within it, as well as the ranges of energy that they may not have (called ''band gaps'' or ''forbidden bands''). Band theory derives these bands and band gaps by examining the allowed quantum mechanical wave functions for an electron in a large, periodic lattice of atoms or molecules. Band theory has been successfully used to explain many physical properties of solids, such as electrical resistivity and optical absorption, and forms the foundation of the understanding of all solid-state devices (transistors, solar cells, etc.). Why bands and band gaps occur The electrons of a single, isolated atom occupy atomic orbitals each of which has a discrete energy level. When two or more atoms join together to form a molecule, their atomic orbitals overlap and hybridize. Similarly, if a large number ''N'' of identical atom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersion Relation
In the physical sciences and electrical engineering, dispersion relations describe the effect of dispersion on the properties of waves in a medium. A dispersion relation relates the wavelength or wavenumber of a wave to its frequency. Given the dispersion relation, one can calculate the phase velocity and group velocity of waves in the medium, as a function of frequency. In addition to the geometry-dependent and material-dependent dispersion relations, the overarching Kramers–Kronig relations describe the frequency dependence of wave propagation and attenuation. Dispersion may be caused either by geometric boundary conditions ( waveguides, shallow water) or by interaction of the waves with the transmitting medium. Elementary particles, considered as matter waves, have a nontrivial dispersion relation even in the absence of geometric constraints and other media. In the presence of dispersion, wave velocity is no longer uniquely defined, giving rise to the distinction o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Vector
In physics, a wave vector (or wavevector) is a vector used in describing a wave, with a typical unit being cycle per metre. It has a magnitude and direction. Its magnitude is the wavenumber of the wave (inversely proportional to the wavelength), and its direction is perpendicular to the wavefront. In isotropic media, this is also the direction of wave propagation. A closely related vector is the angular wave vector (or angular wavevector), with a typical unit being radian per metre. The wave vector and angular wave vector are related by a fixed constant of proportionality, 2π radians per cycle. It is common in several fields of physics to refer to the angular wave vector simply as the ''wave vector'', in contrast to, for example, crystallography. It is also common to use the symbol ''k'' for whichever is in use. In the context of special relativity, ''wave vector'' can refer to a four-vector, in which the (angular) wave vector and (angular) frequency are combined. Def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid State Physics
Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from their atomic-scale properties. Thus, solid-state physics forms a theoretical basis of materials science. It also has direct applications, for example in the technology of transistors and semiconductors. Background Solid materials are formed from densely packed atoms, which interact intensely. These interactions produce the mechanical (e.g. hardness and elasticity), thermal, electrical, magnetic and optical properties of solids. Depending on the material involved and the conditions in which it was formed, the atoms may be arranged in a regular, geometric pattern (crystalline solids, which include metals and ordinary water ice) or irregularly (an amorphous solid such as com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equation Of Motion
In physics, equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time.''Encyclopaedia of Physics'' (second Edition), R.G. Lerner, G.L. Trigg, VHC Publishers, 1991, ISBN (Verlagsgesellschaft) 3-527-26954-1 (VHC Inc.) 0-89573-752-3 More specifically, the equations of motion describe the behavior of a physical system as a set of mathematical functions in terms of dynamic variables. These variables are usually spatial coordinates and time, but may include momentum components. The most general choice are generalized coordinates which can be any convenient variables characteristic of the physical system.''Analytical Mechanics'', L.N. Hand, J.D. Finch, Cambridge University Press, 2008, The functions are defined in a Euclidean space in classical mechanics, but are replaced by curved spaces in relativity. If the dynamics of a system is known, the equations are the solutions for the differential equations describi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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