Physicists at the RIKEN Research Institute in Japan have discovered that hypothetical dark matter particles called axions are capable of generating mysterious strings inside topological insulators. The article by scientists, published in the journal Physics Letters B, is briefly in a press release at Phys.org.
Researchers have studied an unusual phenomenon that occurs inside a topological insulator – a material that is a dielectric (insulator) in volume, but is capable of conducting an electric current on the surface. Typically, when you place a DC conductor in a magnetic field, a transverse voltage (potential difference) occurs, which is called the Hole effect. However, in topological insulators, the anomalous Hole effect occurs when a voltage is generated in the absence of an external magnetic field.
Scientists have come to the conclusion that in topological insulators, when photons and axions interact, extended filamentous configurations – axion strings can appear, which explains the anomalous Hall effect.
Axions have not yet been found. It is believed that these particles can be candidates for the role of dark matter, an invisible mass that affects the motion of cosmic bodies and makes up 80 percent of the matter in the Universe. In addition, they can solve the problem in quantum chromodynamics, which is the violation of CP-invariance. In June 2020, the XENON1T experiment at the Gran Sasso laboratory in Italy reported that they could have detected an axion, but this result has yet to be confirmed.
CP-invariance is called the conservation of physical laws during the operation of mirroring a system with the simultaneous replacement of all particles with antiparticles. However, CP invariance has been shown to be violated in some experiments with weak interactions.