Strongly Dipolar Bose-Einstein Condensates Enable Exploration of Quantum Fluids and New Physics
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The creation of Bose-Einstein condensates using molecules, rather than atoms, represents a significant leap forward in understanding the behaviour of matter at ultra-cold temperatures, and promises to unlock new insights into the realm of quantum fluids. Andreas Schindewolf from TU Wien, Jens Hertkorn from the University of Stuttgart, and Ian Stevenson from Columbia University, alongside their colleagues, investigate the potential of strongly dipolar molecular Bose-Einstein condensates to reveal previously inaccessible states of matter. Their work explores the practical parameters for creating these condensates, identifies suitable molecular species for experimentation, and determines how existing theoretical models can be extended to describe these complex systems. By bridging the gap between few-body and many-body physics, this research establishes a pathway towards resolving long-standing questions in dipolar physics and opens exciting new avenues for exploring exotic quantum phenomena. The study explores how strong dipolar interactions, arising from the electric dipole moments of the molecules, influence the properties of these quantum systems, contributing to a deeper understanding of many-body physics and providing insights into the behaviour of complex quantum systems with long-range interactions, potentially impacting fields such as quantum simulation and materials science. Cryogenic Trapping and Collisional Molecular Cooling Recent advances in molecular cooling now allow scientists to realise strongly dipolar molecules in their lowest energy states. Experiments utilise a cryogenic buffer-gas trap to cool a pulsed beam of YbC molecules, created in a discharge and initially travelling at approximately 600m/s with a temperature around 300 K. Collisions with cold helium gas, at 8 K, cool the molecules both rotationally and translationally, while the trapping potential, created by electric fields, confines them, allowing repeated collisions with the buffer gas. This cooling process relies on interactions between the YbC molecules and the helium buffer gas, favouring transitions to lower energy states. The efficiency of cooling is limited by the low density of helium and potential heating collisions.
The team monitors the rotational distribution of the YbC molecules using laser-induced fluorescence, detecting transitions to excited states, and determines the rotational temperature from the width of the fluorescence signals. Experiments demonstrate cooling of the YbC molecules to a rotational temperature of approximately 40 mK, significantly reducing their kinetic energy. Vibrational cooling, though slower due to weaker coupling, is also investigated, representing a significant step towards controlling the internal and external properties of molecular samples for precision measurements and quantum simulations. Microwave Control of Ultracold Dipolar Molecules Research focuses on manipulating ultracold molecules, particularly dipolar molecules, using microwave fields, a technique crucial for building quantum simulators and exploring many-body physics. Scientists investigate the creation of molecules using laser cooling, photoassociation, and Feshbach resonances, and develop techniques for state selection and preparation, including high-voltage electrode designs. This allows them to shield molecules from unwanted interactions and control their interactions, preparing them in specific quantum states. Microwave shielding reduces unwanted interactions, while microwave-induced state control manipulates molecular states, with dual microwave shielding utilising two frequencies for enhanced control. Scientists search for “magic” wavelengths and frequencies where molecular interactions are insensitive to microwave fields, and explore microwave trapping techniques. These methods enable the investigation of quantum phases such as supersolidity, quantum droplets, and quantum filaments, and facilitate quantum simulation and the exploration of topological phases. Theoretical and computational studies complement experiments, employing potential energy surface calculations, path integral Monte Carlo simulations, and density functional theory to model the behaviour of ultracold molecular systems and provide insights into complex interactions. Researchers also study dynamics and relaxation processes, including thermalisation, collisional relaxation, viscous dynamics, and evaporation, extending investigations to specific molecular species, including NaCs, K2Rb2, NaK, Cs2, and Rb2.
Polar Molecules Achieve Bose-Einstein Condensation Recent research has demonstrated the creation of Bose-Einstein condensates (BECs) using polar molecules, building upon earlier work with magnetic atoms. This achievement opens new avenues for exploring dipolar physics and understanding strongly interacting systems, with molecules, possessing larger electric dipole moments, presenting both unique challenges and opportunities compared to atomic systems, potentially allowing for the exploration of novel collective phenomena. This achievement involved assessing the feasibility of different experimental parameters and techniques for creating and probing these condensates, and pushing the limits of existing theoretical models designed for weakly dipolar gases. Researchers acknowledge that current mean-field theories have limitations in fully describing the complex interactions within these systems, necessitating the use of more advanced computational methods like quantum Monte Carlo simulations. Future work will likely focus on extending these theoretical approaches and exploring the potential for observing phenomena such as dipolar droplets, quantum fluids, and supersolids in molecular BECs, ultimately deepening our understanding of many-body physics and potentially leading to new quantum sensing protocols. 👉 More information 🗞 From few- to many-body physics: Strongly dipolar molecular Bose-Einstein condensates and quantum fluids 🧠 ArXiv: https://arxiv.org/abs/2512.14511 Tags: