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In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter that is typically formed when a gas of bosons at very low densities is cooled to temperatures very close to absolute zero, i.e., 0 K. Under such conditions, a large fraction of bosons occupy the lowest quantum state, at which microscopic quantum-mechanical phenomena, particularly wavefunction interference, become apparent macroscopically. More generally, condensation refers to the appearance of macroscopic occupation of one or several states: for example, in BCS theory, a superconductor is a condensate of Cooper pairs. As such, condensation can be associated with phase transition, and the macroscopic occupation of the state is the order parameter.
In theoretical physics, a roton is an elementary excitation, or quasiparticle, seen in superfluid helium-4 and Bose–Einstein condensates with long-range dipolar interactions or spin-orbit coupling. The dispersion relation of elementary excitations in this superfluid shows a linear increase from the origin, but exhibits first a maximum and then a minimum in energy as the momentum increases. Excitations with momenta in the linear region are called phonons; those with momenta close to the minimum are called rotons. Excitations with momenta near the maximum are called maxons.
Wolfgang Ketterle is a German physicist and professor of physics at the Massachusetts Institute of Technology (MIT). His research has focused on experiments that trap and cool atoms to temperatures close to absolute zero, and he led one of the first groups to realize Bose–Einstein condensation in these systems in 1995. For this achievement, as well as early fundamental studies of condensates, he was awarded the Nobel Prize in Physics in 2001, together with Eric Allin Cornell and Carl Wieman.
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The Gross–Pitaevskii equation describes the ground state of a quantum system of identical bosons using the Hartree–Fock approximation and the pseudopotential interaction model.
In a standard superconductor, described by a complex field fermionic condensate wave function, vortices carry quantized magnetic fields because the condensate wave function is invariant to increments of the phase by . There a winding of the phase by creates a vortex which carries one flux quantum. See quantum vortex.
The Landau–Zener formula is an analytic solution to the equations of motion governing the transition dynamics of a two-state quantum system, with a time-dependent Hamiltonian varying such that the energy separation of the two states is a linear function of time. The formula, giving the probability of a diabatic transition between the two energy states, was published separately by Lev Landau, Clarence Zener, Ernst Stueckelberg, and Ettore Majorana, in 1932.
The Aharonov–Casher effect is a quantum mechanical phenomenon predicted in 1984 by Yakir Aharonov and Aharon Casher, in which a traveling magnetic dipole is affected by an electric field. It is dual to the Aharonov–Bohm effect, in which the quantum phase of a charged particle depends upon which side of a magnetic flux tube it comes through. In the Aharonov–Casher effect, the particle has a magnetic moment and the tubes are charged instead. It was observed in a gravitational neutron interferometer in 1989 and later by fluxon interference of magnetic vortices in Josephson junctions. It has also been seen with electrons and atoms.
Scissors Modes are collective excitations in which two particle systems move with respect to each other conserving their shape. For the first time they were predicted to occur in deformed atomic nuclei by N. LoIudice and F. Palumbo, who used a semiclassical Two Rotor Model, whose solution required a realization of the O(4) algebra that was not known in mathematics. In this model protons and neutrons were assumed to form two interacting rotors to be identified with the blades of scissors. Their relative motion (Fig.1) generates a magnetic dipole moment whose coupling with the electromagnetic field provides the signature of the mode.
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Periodic instantons are finite energy solutions of Euclidean-time field equations which communicate between two turning points in the barrier of a potential and are therefore also known as bounces. Vacuum instantons, normally simply called instantons, are the corresponding zero energy configurations in the limit of infinite Euclidean time. For completeness we add that ``sphalerons´´ are the field configurations at the very top of a potential barrier. Vacuum instantons carry a winding number, the other configurations do not. Periodic instantons were discovered with the explicit solution of Euclidean-time field equations for double-well potentials and the cosine potential with non-vanishing energy and are explicitly expressible in terms of Jacobian elliptic functions. Periodic instantons describe the oscillations between two endpoints of a potential barrier between two potential wells. The frequency of these oscillations or the tunneling between the two wells is related to the bifurcation or level splitting of the energies of states or wave functions related to the wells on either side of the barrier, i.e. . One can also interpret this energy change as the energy contribution to the well energy on either side originating from the integral describing the overlap of the wave functions on either side in the domain of the barrier.
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Spinor condensates are degenerate Bose gases that have degrees of freedom arising from the internal spin of the constituent particles . They are described by a multi-component (spinor) order parameter. Since their initial experimental realisation, a wealth of studies have appeared, both experimental and theoretical, focusing on the physical properties of spinor condensates, including their ground states, non-equilibrium dynamics, and vortices.
Crispin William Gardiner is a New Zealand physicist, who has worked in the fields of quantum optics, ultracold atoms and stochastic processes. He has written about 120 journal articles and several books in the fields of quantum optics, stochastic processes and ultracold atoms.
Thierry Giamarchi is a French physicist.
Christopher John Pethick is a British theoretical physicist, specializing in many-body theory, ultra-cold atomic gases, and the physics of neutron stars and stellar collapse.
Turbulent phenomena are observed universally in energetic fluid dynamics, associated with highly chaotic fluid motion, and typically involving excitations spreading over a wide range of length scales. The particular features of turbulence are dependent on the fluid and geometry, and specifics of forcing and dissipation.
Sung Ryul Eric Yang is a theoretical condensed matter physicist. He is a full professor in the Department of Physics of Korea University.
Leo Radzihovsky is a Russian American condensed matter physicist and academic serving as a professor of Distinction in Physics at the University of Colorado Boulder.
References
- ↑ "Prof. Tin-Lun (Jason) Ho". Department of Physics, The Ohio State University.
- ↑ Mermin, N. D.; Ho, T. L. (March 1976). "Circulation and angular momentum in the A phase of superfluid Helium-3". Physical Review Letters. 36 (11): 594–597. doi:10.1103/PhysRevLett.36.594. (This article has over 500 citations.)
- 1 2 3 4 "Tin-Lun Ho". 2008 Lars Onsager Prize Recipient, American Physical Society.
- ↑ "Tin-Lun Ho". Physics Tree.
- 1 2 3 "Tin-Lun Ho, Curriculum Vita" (PDF). Physics Department, Ohio State University.
- ↑ "Tin-Lun Ho". John Simon Guggenheim Memorial Foundation.
- ↑ "APS Fellow Archive". American Physical Society.
- ↑ "Physics Professors named AAAS Fellows". Department of Physics, Ohio State University. December 8, 2011.
- ↑ "Member Directory, election year 2015, Ohio State University". American Academy of Arts & Sciences.
- ↑ Physicists Discover Important Steps for Making Light Crystals, Research News, Ohio State University, 2009 at the Wayback Machine (archived 2010-06-21)
- ↑ Ho, Tin-Lun; Zhou, Qi (2009). "Squeezing out the entropy of fermions in optical lattices". Proceedings of the National Academy of Sciences. 106 (17): 6916–6920. doi:10.1073/pnas.0809862105. PMC 2678422 .
