Polariton superfluid is predicted to be a state of the
exciton-polaritons
In physics, the exciton–polariton is a type of polariton; a hybrid light and matter quasiparticle arising from the strong coupling of the electromagnetic dipolar oscillations of excitons (either in bulk or quantum wells) and photons. Because ligh ...
system that combines the characteristics of lasers with those of excellent electrical conductors. Researchers look for this state in a solid state
optical microcavity
An optical microcavity or microresonator is a structure formed by reflecting faces on the two sides of a spacer layer or optical medium, or by wrapping a waveguide in a circular fashion to form a ring. The former type is a standing wave cavity, and ...
coupled with
quantum well
A quantum well is a potential well with only discrete energy values.
The classic model used to demonstrate a quantum well is to confine particles, which were initially free to move in three dimensions, to two dimensions, by forcing them to occup ...
exciton
An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb's law, Coulomb force resulting from their opposite charges. It is an electrically neutral quasiparticle regarded as ...
s. The idea is to create an ensemble of particles known as
exciton-polaritons
In physics, the exciton–polariton is a type of polariton; a hybrid light and matter quasiparticle arising from the strong coupling of the electromagnetic dipolar oscillations of excitons (either in bulk or quantum wells) and photons. Because ligh ...
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
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 vortex, vortices that continue to rotate indefinitely. Superfluidity occurs ...
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. Evidence for polariton
superfluidity
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 ...
was reported in by Alberto Amo and coworkers, based on the suppressed scattering of the polaritons during their motion.
Although several other researchers are working in the same field, the terminology and conclusions are not completely shared by the different groups. In particular, important properties of
superfluid
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 vortex, vortices that continue to rotate indefinitely. Superfluidity occurs ...
s, such as zero
viscosity
Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...
, and of
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
s, such as perfect optical
coherence
Coherence is, in general, a state or situation in which all the parts or ideas fit together well so that they form a united whole.
More specifically, coherence, coherency, or coherent may refer to the following:
Physics
* Coherence (physics ...
, are a matter of debate. Although, there is clear indication of
quantized vortices when the pump beam has
orbital angular momentum
Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity – the total angular momentum of a closed sy ...
.
Furthermore, clear evidence has been demonstrated also for superfluid motion of polaritons, in terms of the Landau criterion and the suppression of scattering from defects when the flow velocity is slower than the speed of sound in the fluid.
The same phenomena have been demonstrated in an organic exciton polariton fluid, representing the first achievement of room-temperature superfluidity of a hybrid fluid of photons and excitons.
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See also
*
Bose–Einstein condensation of polaritons
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 las ...
References
{{reflist
External links
YouTube animation explaining what is polariton in a semiconductor micro-resonator.Description of the experimental research on polariton fluids at the Institute of Nanotechnologies.
Phases of matter
Superfluidity