In experiments with specially arranged semiconductors, experts have discovered a new phase of matter, the so-called chiral Bose liquid. As the team led by Rui-Rui Du from Peking University reports, the unusual phase arises in a "frustrated" quantum system in which an imbalance prevents it from assuming a true energetic ground state. As a result, very exotic phenomena can occur in such systems. According to the publication in "Nature", the chiral Bose liquid consists of electrons that assume an ordered state at very low temperatures, in which the individual particles are quantum entangled over long distances. This state is unusually stable and is neither disturbed by interactions with other particles nor by additional magnetic fields. This makes the discovery interesting for stable data storage for quantum computers.
The research group describes their construction as a "frustration machine" for electrons: It can potentially be used to produce many such exotic states of matter. It consists of two semiconductor layers with different properties. The upper layer contains free electrons, while the lower layer contains "holes", i.e. quasi vacancies that behave like positively charged particles and can combine with electrons. Both combine to form quasiparticles, known as excitons. Du's team configured the semiconductors in such a way that the lower one contains many more free holes than the upper one contains electrons. The latter can therefore form excitons of almost the same energy with several holes; as a result, the entire system does not have a clearly defined ground state of lowest energy, which is known as frustration.
The chiral Bose liquid is created because these electrons and holes of the same energy each migrate in channels in which all particles have the same spin orientation. When the working group applies the magnetic field, these channels with different spin orientations move apart. This forms the chiral Bose liquid. This has a number of strange properties. The particles involved are quantum entangled over quite large distances and their common spin orientation is very stable against disturbances. In addition to the at least theoretical possibility of one day using such systems in quantum computers, these frustrated quantum systems are interesting in principle. They are special cases in which particles interact in a very strange way. Due to their exotic properties, new phases of matter such as the chiral Bose liquid could possibly provide new insights into how the subatomic world works as a whole.
