Polariton superfluid
Encyclopedia
Polariton superfluid is predicted to be a state of the exciton-polariton
system that combines the characteristics of lasers with those of excellent electrical conductors. Researchers look for this state in a solid state optical microcavity
coupled with quantum well
exciton
s. The idea is to create an ensemble of particles known as exciton-polariton
s and trap them. Wave behavior in this state results in a light beam similar to that from a laser but possibly more energy efficient.
Unlike traditional superfluid
s that need temperatures of approximately ~4 K, the polariton superfluid could in principle be stable at much higher temperatures, and might soon be demonstrable at room temperature.
Claims of the polariton superfluid appeared in the May 18, 2007, issue of the journal Science
by David Snoke, an associate professor in the physics and astronomy department in the University of Pittsburgh School of Arts and Sciences
. Snoke worked with University of Pittsburgh
graduate students Ryan Balili and Vincent Hartwell on the project and their collaborators at the Bell Labs
of Alcatel-Lucent
in New Jersey
.
Although several other researchers are working in the same field, the Pittsburgh group terminology and conclusions are not completely shared by them. In particular, important properties of superfluid
s, such as zero viscosity
, and of laser
s, such as perfect optical coherence
, are a matter of debate. Although, there is some indication of quantized vortices
when the pump beam has orbital angular momentum.
Polariton
In physics, polaritons are quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation. They are an expression of the common quantum phenomenon known as level repulsion, also known as the anti-crossing principle...
system that combines the characteristics of lasers with those of excellent electrical conductors. Researchers look for this state in a solid state optical microcavity
Optical microcavity
An optical microcavity is a structure formed by reflecting faces on the two sides of a spacer layer or optical medium. The name microcavity stems from the fact that it is often only a few micrometers thick, the spacer layer sometimes even in the nanometer range...
coupled with quantum well
Quantum well
A quantum well is a potential well with only discrete energy values.One technology to create quantization is to confine particles, which were originally free to move in three dimensions, to two dimensions, forcing them to occupy a planar region...
exciton
Exciton
An exciton is a bound state of an electron and hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids...
s. The idea is to create an ensemble of particles known as exciton-polariton
Polariton
In physics, polaritons are quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation. They are an expression of the common quantum phenomenon known as level repulsion, also known as the anti-crossing principle...
s and trap them. Wave behavior in this state results in a light beam similar to that from a laser but possibly more energy efficient.
Unlike traditional superfluid
Superfluid
Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity. The substance, which appears to be a normal liquid, will flow without friction past any surface, which allows it to continue to circulate over obstructions and...
s that need temperatures of approximately ~4 K, the polariton superfluid could in principle be stable at much higher temperatures, and might soon be demonstrable at room temperature.
Claims of the polariton superfluid appeared in the May 18, 2007, issue of the journal Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
by David Snoke, an associate professor in the physics and astronomy department in the University of Pittsburgh School of Arts and Sciences
University of Pittsburgh School of Arts and Sciences
The Kenneth P. Dietrich School of Arts and Sciences is one of the 17 schools and colleges of University of Pittsburgh located in Pittsburgh, PA...
. Snoke worked with University of Pittsburgh
University of Pittsburgh
The University of Pittsburgh, commonly referred to as Pitt, is a state-related research university located in Pittsburgh, Pennsylvania, United States. Founded as Pittsburgh Academy in 1787 on what was then the American frontier, Pitt is one of the oldest continuously chartered institutions of...
graduate students Ryan Balili and Vincent Hartwell on the project and their collaborators at the Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
of Alcatel-Lucent
Alcatel-Lucent
Alcatel-Lucent is a global telecommunications corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services...
in New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
.
Although several other researchers are working in the same field, the Pittsburgh group terminology and conclusions are not completely shared by them. In particular, important properties of superfluid
Superfluid
Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity. The substance, which appears to be a normal liquid, will flow without friction past any surface, which allows it to continue to circulate over obstructions and...
s, such as zero viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
, and of laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s, such as perfect optical coherence
Coherence (physics)
In physics, coherence is a property of waves that enables stationary interference. More generally, coherence describes all properties of the correlation between physical quantities of a wave....
, are a matter of debate. Although, there is some indication of quantized vortices
Quantum vortex
In physics, a quantum vortex is a topological defect exhibited in superfluids and superconductors. Superfluids and superconductors are states of matter without friction. They exist only at very low temperatures. The existence of these quantum vortices was independently predicted by Richard Feynman...
when the pump beam has orbital angular momentum.