The first definition of a quasiparticle
The first person to define a quasiparticle was Lev D. Landau, who conducted studies on superfluidity in 1956. Landau introduced the concept of bosonic quantum liquids (isotope {\displaystyle {ce {^4_2He}}) and fermionic ones ({ce, ^3_2He}}).
The concept of a quasiparticle then arises as an extension of a general excitation of a condensed matter system. It allows to simplify the problem for many objects in quantum mechanics, since quasiparticle dynamics involves simpler equations
Majorana's hypothesis
One of the first quasiparticles discovered was the electron hole. In other words, the absence of an electron where it should be. Physicists in the 1940s discovered that holes jump around inside solids as positively charged particles.
Majorana gave a further definition of quasiparticles as objects with a dual nature. In fact, they are half electron and half hole at the same time.
In 2010, Das Sarma and his collaborators argued that Majorana's quasiparticles could be used to create quantum computers. When you twist the electron and the gap around each other, they store information, like a pattern woven into two strings. Different twists correspond to the 1s, 0s, and superpositions of 1s and 0s that are the bits of quantum computers.
Quantum computers
Efforts to build effective quantum computers have so far stumbled because the quantum superpositions of most types of particles break down when they get too hot or when they collide with other particles. Not so with Majorana quasiparticles. Their unusual composition gives them zero energy and zero charge, theoretically allowing them to exist in the depths of a type of superconductor, a material that conducts electricity without resistance.
Classification of quasiparticles
Only 17 particles are called "fundamental" because they are believed to be the building blocks of all material reality. Quasiparticles are created by interactions between a large number of these fundamental particles. Taking a solid, liquid, or plasma composed of a large number of particles and subjecting it to extreme temperatures and pressures, the resulting system can be described as a few robust, particle-like entities. The resulting quasiparticles can be quite stable, with well-defined properties such as mass and charge.
An example of a quasiparticle: polarons
One example of a quasiparticle is the polaron. It consists of an electron and an electric polarization field. The electron moves in a crystal by interacting with ions and is surrounded by a lattice polarization region caused by the lattice deformation of the ions. The electron attracts positively charged ions and will form a phonon cloud.
Polarons were discovered in 1933 by Lev Landau. These quasiparticles are also mentioned in Star Trek: Voyager in 1995. The main characteristic is that they are created when many electrons are trapped inside a crystal. The momentum and attraction between each electron and all the particles in its environment "dress" the electron so that it behaves like a quasiparticle with a higher mass.
Black holes made of polarons
The wide variety of quasiparticles allows physicists to construct analogues of other systems that are difficult or impossible to access, such as black holes.
A fluid phase map reveals their vortex-like flow.
Black holes form in the cosmos wherever gravity becomes so strong that even light cannot escape. An analog can be created with polaritons. Researchers use two mirrors to trap a photon in a cage that also contains an exciton, itself a type of quasiparticle consisting of an electron and a gap orbiting each other.
Research in recent years
Recent research in condensed matter suggests that it is possible to create quasiparticles that have a precise fraction of the charge or spin of the electron - a kind of intrinsic angular momentum. It is still unclear how these exotic properties are produced, to the point that researchers at the University of Maryland have described it as a magical effect.
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