Superfluid helium-4 is the superfluid form of helium-4, an isotope of the element helium. A superfluid is a state of matter in which matter behaves like a fluid with zero viscosity. The substance, which looks like a normal liquid, flows without friction past any surface, which allows it to continue to circulate over obstructions and through pores in containers which hold it, subject only to its own inertia.
Sonoluminescence is the emission of light from imploding bubbles in a liquid when excited by sound.
Triboluminescence is a phenomenon in which light is generated when a material is mechanically pulled apart, ripped, scratched, crushed, or rubbed. The phenomenon is not fully understood but appears in most cases to be caused by the separation and reunification of static electric charges, see also triboelectric effect. The term comes from the Greek τρίβειν and the Latin lumen (light). Triboluminescence can be observed when breaking sugar crystals and peeling adhesive tapes.
The triboelectric effect describes electric charge transfer between two objects when they contact or slide against each other. It can occur with different materials, such as the sole of a shoe on a carpet, or between two pieces of the same material. It is ubiquitous, and occurs with differing amounts of charge transfer (tribocharge) for all solid materials. There is evidence that tribocharging can occur between combinations of solids, liquids and gases, for instance liquid flowing in a solid tube or an aircraft flying through air.
Quantum turbulence is the name given to the turbulent flow – the chaotic motion of a fluid at high flow rates – of quantum fluids, such as superfluids. The idea that a form of turbulence might be possible in a superfluid via the quantized vortex lines was first suggested by Richard Feynman. The dynamics of quantum fluids are governed by quantum mechanics, rather than classical physics which govern classical (ordinary) fluids. Some examples of quantum fluids include superfluid helium, Bose–Einstein condensates (BECs), polariton condensates, and nuclear pasta theorized to exist inside neutron stars. Quantum fluids exist at temperatures below the critical temperature at which Bose-Einstein condensation takes place.
In condensed matter physics, a supersolid is a spatially ordered material with superfluid properties. In the case of helium-4, it has been conjectured since the 1960s that it might be possible to create a supersolid. Starting from 2017, a definitive proof for the existence of this state was provided by several experiments using atomic Bose–Einstein condensates. The general conditions required for supersolidity to emerge in a certain substance are a topic of ongoing research.
A fermionic condensate is a superfluid phase formed by fermionic particles at low temperatures. It is closely related to the Bose–Einstein condensate, a superfluid phase formed by bosonic atoms under similar conditions. The earliest recognized fermionic condensate described the state of electrons in a superconductor; the physics of other examples including recent work with fermionic atoms is analogous. The first atomic fermionic condensate was created by a team led by Deborah S. Jin using potassium-40 atoms at the University of Colorado Boulder in 2003.
John Frank Allen, FRS FRSE was a Canadian-born physicist. At the same time as Pyotr Leonidovich Kapitsa in Moscow, Don Misener and Allen independently discovered the superfluid phase of matter in 1937 using liquid helium in the Royal Society Mond Laboratory in Cambridge, England.
Pyroelectric fusion refers to the technique of using pyroelectric crystals to generate high strength electrostatic fields to accelerate deuterium ions (tritium might also be used someday) into a metal hydride target also containing deuterium (or tritium) with sufficient kinetic energy to cause these ions to undergo nuclear fusion. It was reported in April 2005 by a team at UCLA. The scientists used a pyroelectric crystal heated from −34 to 7 °C (−29 to 45 °F), combined with a tungsten needle to produce an electric field of about 25 gigavolts per meter to ionize and accelerate deuterium nuclei into an erbium deuteride target. Though the energy of the deuterium ions generated by the crystal has not been directly measured, the authors used 100 keV (a temperature of about 109 K) as an estimate in their modeling. At these energy levels, two deuterium nuclei can fuse to produce a helium-3 nucleus, a 2.45 MeV neutron and bremsstrahlung. Although it makes a useful neutron generator, the apparatus is not intended for power generation since it requires far more energy than it produces.
Lithium tantalate is the inorganic compound with the formula LiTaO3. It is a white, diamagnetic, water-insoluble salt. The compound has the perovskite structure. It has optical, piezoelectric, and pyroelectric properties that make it valuable for nonlinear optics, passive infrared sensors such as motion detectors, terahertz generation and detection, surface acoustic wave applications, cell phones. Considerable information is available from commercial sources about this material.
A quantum gyroscope is a very sensitive device to measure angular rotation based on quantum mechanical principles. The first of these was built by Richard Packard and his colleagues at the University of California, Berkeley. The extreme sensitivity means that theoretically, a larger version could detect effects like minute changes in the rotational rate of the Earth.
In physics, a quantum vortex represents a quantized flux circulation of some physical quantity. In most cases, quantum vortices are a type of topological defect exhibited in superfluids and superconductors. The existence of quantum vortices was first predicted by Lars Onsager in 1949 in connection with superfluid helium. Onsager reasoned that quantisation of vorticity is a direct consequence of the existence of a superfluid order parameter as a spatially continuous wavefunction. Onsager also pointed out that quantum vortices describe the circulation of superfluid and conjectured that their excitations are responsible for superfluid phase transitions. These ideas of Onsager were further developed by Richard Feynman in 1955 and in 1957 were applied to describe the magnetic phase diagram of type-II superconductors by Alexei Alexeyevich Abrikosov. In 1935 Fritz London published a very closely related work on magnetic flux quantization in superconductors. London's fluxoid can also be viewed as a quantum vortex.
A macroscopic quantum state is a state of matter in which macroscopic properties, such as mechanical motion, thermal conductivity, electrical conductivity and viscosity, can be described only by quantum mechanics rather than merely classical mechanics. This occurs primarily at low temperatures where little thermal motion is present to mask the quantum nature of a substance.
Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two isotopes of helium when they are liquefied by cooling to cryogenic temperatures. It is also a property of various other exotic states of matter theorized to exist in astrophysics, high-energy physics, and theories of quantum gravity. The theory of superfluidity was developed by Soviet theoretical physicists Lev Landau and Isaak Khalatnikov.
Immanuel Bloch is a German experimental physicist. His research is focused on the investigation of quantum many-body systems using ultracold atomic and molecular quantum gases. Bloch is known for his work on atoms in artificial crystals of light, optical lattices, especially the first realization of a quantum phase transition from a weakly interacting superfluid to a strongly interacting Mott insulating state of matter.
Tilman Esslinger is a German experimental physicist. He is Professor at ETH Zurich, Switzerland, and works in the field of ultracold quantum gases and optical lattices.
Bose–Einstein condensation of polaritons is a growing field in semiconductor optics research, which exhibits spontaneous coherence similar to a laser, but through a different mechanism. A continuous transition from polariton condensation to lasing can be made similar to that of the crossover from a Bose–Einstein condensate to a BCS state in the context of Fermi gases. Polariton condensation is sometimes called “lasing without inversion”.
Egor Babaev is a Russian-born Swedish physicist. In 2001, he received his PhD in theoretical physics from Uppsala University (Sweden). In 2006 he joined the faculty of the KTH Royal Institute of Technology in Stockholm. In 2007-2013 he shared this position with a faculty appointment at Physics Department of the University of Massachusetts, Amherst (USA). He is currently full professor at the Physics Department KTH Royal Institute of Technology.
Victor Malka is a French plasma physicist and a pioneer in laser plasma acceleration. In 2004, Malka demonstrated that high energy monoenergetic electron beams could be generated using the technique of laser wakefield acceleration, and subsequently used them to develop compact X-ray and gamma radiation sources with applications in medicine, security technology and phase-contrast imaging. For these contributions to the field, he was awarded the IEEE Particle Accelerator Science and Technology Award in 2007, the Julius Springer Prize for Applied Physics in 2017, and the Hannes Alfvén Prize in 2019.
Max Born was a widely influential German physicist and mathematician who was awarded the 1954 Nobel Prize in Physics for his pivotal role in the development of quantum mechanics. Born won the prize primarily for his contributions to the statistical interpretation of the wave function, though he is known for his work in several areas of quantum mechanics as well as solid-state physics, optics, and special relativity. Born's entry in the Biographical Memoirs of Fellows of the Royal Society included thirty books and 330 papers.
