Exploration of exotic quantum phase transitions has always been a focus in condensed matter physics. Critical phenomena in a phase transition are entirely determined by the universality class, which is controlled by the spatial and/or order-parameters and is independent of microscopic details.
The quantum phase transition is a class of phase transitions that occurs due to quantum fluctuations, tuned by certain parameters of the system at the zero-temperature limit. The superconductor-insulator/metal phase transition is a classic example of quantum phase transition, which has been intensely studied for more than 40 years.
Disorder is considered one of the most important influencing factors, and therefore has received widespread attention. During the phase transitions, the system usually satisfies scaling invariance, so the universality class will be characterized by a single critical exponent. In contrast, the peculiarity of quantum Griffith singularity is that it breaks the traditional scaling invariance, where exotic physics emerges.
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