Phase transitions in systems with a finite number of dominant ground states

Joseph Marie Thijssen

Zheng-Da Hu, Wei Zhong, Jicheng Wang +2 more

Quantum phase transition is a fundamental physical phenomenon in a quantum many-body system. This work aims to explore the quantum phase transition in an atom–molecule conversion system through quantum information tools. We show that the ground state of the system undergoes significant changes in the quantum critical region, with both atomic number fluctuation and the quantum information embedded in the ground state exhibiting drastic alterations. As the rescaled phase transition parameter increases, the atomic state sharply transits into the molecular state in the critical region. Even for finite total number, the phase transition point can be accurately predicted through finite-size scaling laws. Our study confirms that the finite-size scaling analysis based on quantum coherence and quantum Fisher information is a reliable method for studying critical phenomena in the atom–molecule system from a quantum information perspective.

Ph. Chomaz, Veronique DUFLOT, Francesca Gulminelli

Liliana Arrachea, N. Canosa, Angelo Plastino +2 more

A scheme for detecting signatures of phase transitions associated with pure quantum states, from the knowledge of a limited set of expectation values, is introduced. An accurate prediction of critical regions in ground states of systems with a finite number of particles is obtained.

Tsz Hin Hui, Xiaodan Xia, Pedro D. Sacramento +1 more

We introduce a general scheme for constructing order parameters (OPs) by extracting generic patterns from the dominant Fock states of many-body ground states. While topological phases are traditionally characterized by non-local invariants, we demonstrate that our real-space OPs provide a more refined classification. In the extended Su-Schrieffer-Heeger model, we show that the standard winding number is insufficient to fully distinguish all phases; our OPs reveal a hidden sub-structure where each topological sector splits into two distinct phases. Beyond identifying the phase boundaries, these OPs quantify the depth of a phase, and remain robust in characterizing transitions in disordered systems. Furthermore, our approach provides a practical finite-size diagnostic for the Berezinskii-Kosterlitz-Thouless transition in the interacting spin-1/2 XXZ model. The presented framework offers a broadly applicable tool for uncovering the phase diagrams of diverse interacting and non-interacting quantum many-body systems.

E. D. D. Davis, H. G. Miller