Apart from the states of matter that we are all aware of and accustomed to, which correspond to solids, liquids, and gases, more exotic states can be generated in specific materials under special conditions. Such states are of great interest to physicists because they help them gain a deeper understanding of quantum phenomena, which is key for scientists and engineers to innovate state-of-the-art technology.
Bose-Einstein condensate is one such state of matter that occurs at very low temperatures. In this state, most of the constituent particles of the condensate are in the so-called "ground state," which is the state with the lowest energy, and microscopic quantum phenomena can be easily observed. Interestingly, this state can also be exhibited by quasiparticles, which are not actual particles but represent collective microscopic excitations in a system and can be thus used to describe the system in a simplified, yet very useful manner. Magnons, a type of quasiparticle that manifests in magnetic materials, are collective excitations originating from electrons in a crystal. Magnons can normally hop between different locations in the crystal; however, in some compounds and under the effect of a magnetic field, they can be trapped in a kind of catch-22 situation, which results in them exhibiting rigid crystallinity. This is a very interesting quantum phenomenon called "magnon crystallization," where the magnons are said to be in a 'frustrated' state.
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