Fumika Suzuki, Rajesh K. Malla, Nikolai A. Sinitsyn,
Competing Bosonic Reactions: Insight from Exactly Solvable Time-Dependent Models,
arXiv:2504.13027 (2025)

We discuss the progress on exactly solvable multistate Landau-Zener models from the perspective of their application to competing reactions of particle creation from a false vacuum. Such models generally predict that, even with identical initial conditions and nearly the same other particle parameters, quantum coherent evolution results in a final particle distribution with significant asymmetry. We use an exact solution of the driven bosonic Tavis-Cummings model for two reaction pathways to quantify this effect, reveal a corresponding phase transition, and identify its universality class. These studies of quantum phase transitions can be relevant to quantum optics, condensed matter physics, quantum simulations, as well as cosmology and high-energy physics.

Fumika Suzuki, and W. H. Zurek,
Dynamics of the order parameter in symmetry breaking phase transitions,
arXiv:2412.15568 (2024)

The formation of topological defects in second-order phase transitions can be studied by solving partial differential equations for the order parameter, such as the Langevin equation. We show that the ordinary differential equations governing the temporal or spatial evolution provide key insights into the dynamics of the phase transition. The temporal evolution predicts aspects of the adiabatic-impulse scenario, including freeze-out time scaling essential to the Kibble-Zurek mechanism (KZM). In particular, Bernoulli equations can be solved analytically in the overdamped case. The spatial evolution determines the characteristic domain size. This approach not only offers fundamental insights into KZM solely by ordinary differential equations but also enables exploration of Kibble-Zurek scaling over a broad range of quench timescales, which would be challenging with numerical simulations of full partial differential equations.

*Answers to some common questions:
We occasionally receive questions referring to theorems derived for equilibrium systems. However, the Kibble-Zurek mechanism addresses "non-equilibrium" dynamics during critical quenches. Please be mindful of the assumptions under which those mathematical theorems were proved.

Fumika Suzuki, and W. H. Zurek,
Topological defect formation in a phase transition with tunable order,
Phys. Rev. Lett. 132, 241601 (2024)
APS Physics Magazine
LANL News
Supplementary Movie
Poster Presentation
The Kibble-Zurek mechanism (KZM) describes the non-equilibrium dynamics and topological defect formation in systems undergoing second-order phase transitions. KZM has found applications in fields such as cosmology and condensed matter physics. KZM is generally applicable only to second-order phase transitions. However, here we extend the applicability of KZM to first-order phase transitions by combining it with nucleation theory.

*Answers to some common questions:
- We occasionally receive questions referring to theorems derived for equilibrium systems. However, the Kibble-Zurek mechanism addresses "non-equilibrium" dynamics during critical quenches. Please be mindful of the assumptions under which those mathematical theorems were proved.

- Q: Can I use the potential of the form V = φ⁶ - ε φ² - c φ⁴ for a weakly first-order phase transition?
  A: Yes, you can. It gives results (of course) very similar to those presented in the paper.

Bhavay Tyagi, Fumika Suzuki, Vladimir A. Chernyak, Nikolai A. Sinitsyn,
Asymmetry Amplification by a Nonadiabatic Passage through a Critical Point,
Phys. Rev. A 111, 032205 (2025)

We propose and solve a minimal model of dynamic passage through a second-order phase transition in the presence of symmetry-breaking interactions and no dissipation. It turns out that the evolution eventually leads to a highly asymmetric state, regardless of how weak the symmetry-breaking parameter of the Hamiltonian is.

Vijay Ganesh Sadhasivam, Fumika Suzuki, Bin Yan, Nikolai A. Sinitsyn,
Parametric tuning of dynamical phase transitions in ultracold reactions,
Nat. Commun. 15, 10246 (2024)

A coherent transformation between ultracold atoms and molecules, including between completely bosonic condensates, is enabled by the magneto-association of atoms at a Feshbach resonance, which results in a passage through a quantum critical point. In this study, we show that the presence of generic interactions between the constituent atoms and molecules can fundamentally alter the nature of the critical point, change the yield of the reaction, and modify the order of the consequent phase transition. Furthermore, we demonstrate that non-adiabatic excitations in a first-order quantum phase transition can be described by the sum of Kibble-Zurek scaling and a first-order correction, similarly to the result presented in Phys. Rev. Lett. 132, 241601 (2024).

Nikolai A. Sinitsyn, Vijay Ganesh Sadhasivam, Fumika Suzuki,
Nonadiabatic transitions during a passage near a critical point,
J. Chem. Phys. 160, 074104 (2024)

The study of nonadiabatic excitations that emerge during a slow passage through a quantum critical point is crucial for quantum annealing computers, and also has applications in cosmology, quantum metrology and control. We derived the exact number of excitations analytically within a regime where a system pass in the vicinity of the critical point without crossing it.