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Dephasing
In physics, dephasing is a mechanism that recovers classical behaviour from a quantum system. It refers to the ways in which coherence caused by perturbation decays over time, and the system returns to the state before perturbation. It is an important effect in molecular and atomic spectroscopy, and in the condensed matter physics of mesoscopic devices. The reason can be understood by describing the conduction in metals as a classical phenomenon with quantum effects all embedded into an effective mass that can be computed quantum mechanically, as also happens to resistance that can be seen as a scattering effect of conduction electrons. When the temperature is lowered and the dimensions of the device are meaningfully reduced, this classical behaviour should disappear and the laws of quantum mechanics should govern the behavior of conducting electrons seen as waves that move ballistically inside the conductor without any kind of dissipation. Most of the time this is what one o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dephasing Rate SP Formula
The ''SP'' formula for the dephasing rate \Gamma_ of a particle that moves in a fluctuating environment unifies various results that have been obtained, notably in condensed matter physics Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter, especially the solid and liquid phases which arise from electromagnetic forces between atoms. More generally, the sub ..., with regard to the motion of electrons in a metal. The general case requires to take into account not only the temporal correlations but also the spatial correlations of the environmental fluctuations. These can be characterized by the spectral form factor \tilde(q,\omega), while the motion of the particle is characterized by its power spectrum \tilde(q,\omega). Consequently, at finite temperature the expression for the dephasing rate takes the following form that involves ''S'' and ''P'' functions: \Gamma_ \ = \ \int d \int \frac \,\tilde(,\om ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spin Echo
In magnetic resonance, a spin echo or Hahn echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) make use of this effect. The NMR signal observed following an initial excitation pulse decays with time due to both spin relaxation and any ''inhomogeneous'' effects which cause spins in the sample to precess at different rates. The first of these, relaxation, leads to an irreversible loss of magnetisation. But the inhomogeneous dephasing can be removed by applying a 180° ''inversion'' pulse that inverts the magnetisation vectors. Examples of inhomogeneous effects include a magnetic field gradient and a distribution of chemical shifts. If the inversion pulse is applied after a period ''t'' of dephasing, the inhomogeneous evolution will rephase to form an echo at time 2''t''. In simple cases, the intensity of the echo relative to the initial signal is given by ''e– ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spin–spin Relaxation
In physics, the spin–spin relaxation is the mechanism by which , the transverse component of the magnetization vector, exponentially decays towards its equilibrium value in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). It is characterized by the spin–spin relaxation time, known as 2, a time constant characterizing the signal decay. It is named in contrast to 1, the spin–lattice relaxation time. It is the time it takes for the magnetic resonance signal to irreversibly decay to 37% (1/ e) of its initial value after its generation by tipping the longitudinal magnetization towards the magnetic transverse plane. Hence the relation :M_(t) = M_(0) e^ \,. 2 relaxation generally proceeds more rapidly than 1 recovery, and different samples and different biological tissues have different 2. For example, fluids have the longest 2 (on the order of seconds for protons), and water based tissues are in the 40–200 ms range, while fat based tissues are in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boris Altshuler
Boris Leonidovich Altshuler (russian: Бори́с Леонидович Альтшу́лер, born 27 January 1955, Saint Petersburg, Leningrad, Soviet Union, USSR) is a professor of theoretical physics at Columbia University. His specialty is theoretical condensed matter physics. Education and career Altshuler attended State Secondary School 489 in Saint Petersburg. He received his diploma in physics from Leningrad State University in 1976. Altshuler continued on at the Leningrad Institute for Nuclear Physics, where he was awarded his Ph.D. in physics in 1979. Altshuler stayed at the institute for the next ten years as a research fellow. In 1989, Altshuler joined the faculty of the Massachusetts Institute of Technology. While there, he received the Hewlett-Packard Europhysics Prize (now called the Agilent Physics Prize) and became a fellow of the American Physical Society. Altshuler left MIT in 1996 to take a professorship at Princeton University. While there, he became affiliat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arkady Aronov
Arkady Girshevich Aronov (russian: Аркадий Гиршевич Аронов; July 26, 1939 in Leningrad, Soviet Union – November 13, 1994 in Rehovot, Israel) was a Russian and Israeli theoretical condensed matter physicist, notable for his achievements in physics of semiconductors and in mesoscopic physics. Biography Aronov was born in 1939 in Leningrad, currently Saint Petersburg, and in 1962 graduated from the Leningrad Electrotechnical Institute. He got his PhD degree from the Institute of Semiconductors of Russian Academy of Sciences in 1966 under supervision of Grigory Pikus. The title of his thesis was "Magnetic phenomena in crossed electric and magnetic fields". He stayed to work at the same institute as a researcher. In 1972, the Institute of Semiconductors was merged with into Ioffe Physical-Technical Institute. In 1974, Aronov moved to the Konstantinov Leningrad Nuclear Physics Institute, located in Gatchina. In 1977, he received there his Doktor nauk degree for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cavity Dephasing Simulation
Cavity may refer to: Biology and healthcare *Body cavity, a fluid-filled space in many animals where organs typically develop **Gastrovascular cavity, the primary organ of digestion and circulation in cnidarians and flatworms *Dental cavity or tooth decay, damage to the structure of a tooth *Lung cavity, an air-filled space within the lung Radio frequency resonance * Microwave cavity or ''RF cavity'', a cavity resonator in the radio frequency range, for example used in particle accelerators * Optical cavity, the cavity resonator of a laser * Resonant cavity, a device designed to select for waves of particular wavelengths Other uses *Cavity (band), a sludge metal band from Miami, Florida *Cavity method, a mathematical method to solve some mean field type of models *Cavity wall, a wall consisting of two skins with a cavity See also * Cavitation, the phenomenon of partial vacuums forming in fluid, for example, in propellers * Cavitary pneumonia, a type of pneumonia in which a hole ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum State
In quantum physics, a quantum state is a mathematical entity that provides a probability distribution for the outcomes of each possible measurement on a system. Knowledge of the quantum state together with the rules for the system's evolution in time exhausts all that can be predicted about the system's behavior. A mixture of quantum states is again a quantum state. Quantum states that cannot be written as a mixture of other states are called pure quantum states, while all other states are called mixed quantum states. A pure quantum state can be represented by a ray in a Hilbert space over the complex numbers, while mixed states are represented by density matrices, which are positive semidefinite operators that act on Hilbert spaces. Pure states are also known as state vectors or wave functions, the latter term applying particularly when they are represented as functions of position or momentum. For example, when dealing with the energy spectrum of the electron in a hydrogen at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Review Letters
''Physical Review Letters'' (''PRL''), established in 1958, is a peer-reviewed, scientific journal that is published 52 times per year by the American Physical Society. As also confirmed by various measurement standards, which include the ''Journal Citation Reports'' impact factor and the journal ''h''-index proposed by Google Scholar, many physicists and other scientists consider ''Physical Review Letters'' to be one of the most prestigious journals in the field of physics. ''According to Google Scholar, PRL is the journal with the 9th journal h-index among all scientific journals'' ''PRL'' is published as a print journal, and is in electronic format, online and CD-ROM. Its focus is rapid dissemination of significant, or notable, results of fundamental research on all topics related to all fields of physics. This is accomplished by rapid publication of short reports, called "Letters". Papers are published and available electronically one article at a time. When published in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxford University Press
Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print books by decree in 1586, it is the second oldest university press after Cambridge University Press. It is a department of the University of Oxford and is governed by a group of 15 academics known as the Delegates of the Press, who are appointed by the vice-chancellor of the University of Oxford. The Delegates of the Press are led by the Secretary to the Delegates, who serves as OUP's chief executive and as its major representative on other university bodies. Oxford University Press has had a similar governance structure since the 17th century. The press is located on Walton Street, Oxford, opposite Somerville College, in the inner suburb of Jericho. For the last 500 years, OUP has primarily focused on the publication of pedagogical texts and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-resolved Spectroscopy
In physics and physical chemistry, time-resolved spectroscopy is the study of dynamic processes in materials or chemical compounds by means of spectroscopic techniques. Most often, processes are studied after the illumination of a material occurs, but in principle, the technique can be applied to any process that leads to a change in properties of a material. With the help of pulsed lasers, it is possible to study processes that occur on time scales as short as 10−16 seconds. All time-resolved spectra are suitable to be analyzed using the two-dimensional correlation method for a correlation map between the peaks. Transient-absorption spectroscopy Transient-absorption spectroscopy (TAS), also known as flash photolysis, is an extension of absorption spectroscopy. Ultrafast transient absorption spectroscopy, an example of non-linear spectroscopy, measures changes in the absorbance/transmittance in the sample. Here, the absorbance at a particular wavelength or range of wavelengths ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fourier Transform
A Fourier transform (FT) is a mathematical transform that decomposes functions into frequency components, which are represented by the output of the transform as a function of frequency. Most commonly functions of time or space are transformed, which will output a function depending on temporal frequency or spatial frequency respectively. That process is also called ''analysis''. An example application would be decomposing the waveform of a musical chord into terms of the intensity of its constituent pitches. The term ''Fourier transform'' refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of space or time. The Fourier transform of a function is a complex-valued function representing the complex sinusoids that comprise the original function. For each frequency, the magnitude (absolute value) of the complex value represents the amplitude of a constituent complex sinusoid with that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spin–lattice Relaxation
During nuclear magnetic resonance observations, spin–lattice relaxation is the mechanism by which the longitudinal component of the total nuclear magnetic moment vector (parallel to the constant magnetic field) exponentially relaxes from a higher energy, non-equilibrium state to thermodynamic equilibrium with its surroundings (the "lattice"). It is characterized by the spin–lattice relaxation time, a time constant known as ''T1''. There is a different parameter, ''T2'', the spin-spin relaxation time, which concerns the exponential relaxation of the transverse component of the nuclear magnetization vector ( to the external magnetic field). Measuring the variation of ''T1'' and ''T2'' in different materials is the basis for some magnetic resonance imaging techniques. Nuclear physics ''T1'' relaxation or longitudinal relaxation curve ''T1'' characterizes the rate at which the longitudinal ''Mz'' component of the magnetization vector recovers exponentially towards its thermodynam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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