The Secret Switch that Decides How Quantum Matter Changes

 

Most phase transitions, like water freezing, follow wellknown rules. Nevertheless, in quantum physics , there is a rare type of change where one ordered state turns directly into a different ordered state without becoming disordered in between. These unusual points are called deconfined quantum critical points (DQCPs), and their true behaviour has been debated for years.

Physicists at HKU provide a clearer answer. Using largescale quantum Monte Carlo simulations, the team examined entanglement entropy, which reveals how strongly different parts of a quantum system are linked beneath the surface.

 

The key result is that DQCPs do not behave the same in all systems. Their behaviour depends on a parameter
called N, which describes the symmetry of the system:

 

Identifying this threshold gives scientists a solid guide for when DQCPs behave predictably, paving the way for future research in quantum materials and technology.

 

量子物理中存在一種罕見轉變，物質可在不經無序階段下，直接由一種有序狀態變成另一種有序狀態，稱為解禁閉量子臨界點。我們的物理學團隊利用大規模量子蒙地卡羅模擬，觀察糾纏熵的變化，發現其行為取決於系統對稱性的參數 N：當 N 較大時，轉變呈現平滑連續；當 N 較小時，則出現較突兀的異常特徵。此結果釐清解禁閉量子臨界點的關鍵分界，為未來量子材料與相關研究提供重要指引。