A collaboration between physicists from Zhejiang University and Rice University in Houston establishes a new means of probing quantum entanglement of strange metals at a quantum critical point.

Just like water vaporizes or freezes upon the variation of thermal fluctuations, matter can undergo transformation from one quantum phase to another through the control of quantum fluctuations. A quantum critical point develops at a continuous quantum phase transition, and is expected to possess amplified quantum entanglement. This is the spooky action at a distance as Albert Einstein called it, which may drive such technologies as quantum computing.

In this work, which was published in Physical Review Letters, Cai et al. focus on an idealized but realistic model for quantum materials, featuring strongly correlated electrons at the border of itinerancy and localization. Only the spin degrees of freedom of the model interact with each other, and conventional expectation is that only physical quantities made up of the spins will be critical. Surprisingly, they show that quantities from the charge sector are also critical. These results provide a theoretical basis to understand the striking puzzles raised by recent experiments in “heavy fermion metals” and indicate new means to probe the quantum entanglement of electrons in a broad range of quantum materials.