Decaying of macroscopic quantum objects in far from equilibrium Bose-Einstein condensates

• Grant number: 24/20641-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: April 01, 2025
• End date: August 31, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Principal Investigator: Vanderlei Salvador Bagnato
• Grantee: Leandro Alvares Machado
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

Although the decay of excited atomic states, driven by interactions with external modes, is relatively well understood, the same phenomenon in many-body systems remains largely unexplored. Just as external modes coupled to an atom determine its decay, a similar mechanism should apply to many- body systems. In this project, we will use an interacting Bose-Einstein condensate (BEC) as our many-body system to investigate the decay of multicharged vortices, considered as a superfluid excitation. Analogous to excited atoms, multicharged vortices are expected to decay into singly quantized vortices. This decay can either be accelerated or delayed, depending on how the vortex interacts with the superfluid environment. This dynamic is comparable to "cavity quantum electrodynamics" (QED) but involves macroscopic quantum objects, representing a novel phenomenon. In the proposed study, we will simulate the introduction of vortices with charge |q| = 2 or |q| = 4 into a condensate trapped by an external potential, examining their decay under various external conditions. These conditions will include temporal fluctuations in the potential, variations in the two-body interaction (scattering length), thermal fluctuations, and configurations where two vortices with |q| = 2 coexist within the same superfluid to explore how one vortex influences the decay of the other. Delta-like repulsive impurities in an oscillatory regime will also be introduced to complement the analysis of vortex decay. Additionally, we will consider thermal fluctuations and analyze their influence on the system in various equilibrium states, from the presence of few vortices to complete coherence loss. We will observe processes of dynamic stabilization and decay stimulation, as well as the impact of the sound wave spectrum on the decay behavior. This study aims to reveal novel effects on the stability and decay modes of macroscopic quantum objects, allowing for the identification of dynamic stabilization processes and decay stimulation. Finally, we will explore how these phenomena influence the generation and decay of turbulence in the superfluid, investigating the relaxation pathways that the system assumes towards the equilibrium and comparing them with the spontaneous phase ordering process in superfluid formation, governed by the Kibble-Zurek mechanism.