Periodic Reporting for period 3 - NEWMAT (Supersolids and Beyond: Exploring New States of Matter with Laser-Cooled Dipolar Molecules)
Reporting period: 2023-10-01 to 2024-12-31
The project focusses on the exploration of novel quantum states of matter using ultracold molecules. Such cold molecules are highly sought-after because they combine complex interactions with a rich internal structure. In particular, they feature large and tunable electric dipole moments that are known to be responsible for the emergence of supersolid states of matter. These supersolids, counterintuitively, combine the frictionless flow of a superfluid with the rigid structure of a crystal. After 60 years of searching, supersolids have only recently been observed using dipolar atoms. There are still many open questions about their properties, which we want to clarify with the help of the ultracold molecules. While these questions are fundamental research, cooling of molecules also sets the stage for the exploitation of molecular quantum effects in future real-life devices, very much in line with the agenda of the EU Quantum Flagship.
We have designed and are setting up a new experimental apparatus for the laser cooling of calcium monofluoride (CaF) molecules. The design is based around a cryogenic molecular source, in which molecules are formed by laser ablation. This source has been optimized extensively, in order to provide the largest number of molecules possible. The molecules emerge from this source as a molecular beam, which will be cooled transversally and, subsequently, slowed and trapped to near standstill. For this, we use the technique of molecular laser cooling, for which extensive laser systems have been designed and set up. Following laser cooling, further collisional cooling will be required to bring the molecular gas to the quantum regime, where supersolids can be investigated. In preparation for this, we have investigated the collisional properties of the molecules theoretically and, based on this, are designing microwave electrodes to control these collisional properties in our favor. Important theoretical work has been aimed at theoretically exploring the resulting many-body states of the molecules. Finally, in order to realize compact single-molecule manipulation, we have pioneered a new approach to optical tweezers for atoms and molecules based on 3D printed optics.
Our results have been disseminated to the scientific community at international conferences and meetings.
Due to the pandemic and the move of the experiment from Stuttgart to Vienna, participation in outreach activities to promote our research to younger physics and highschool students (e.g. through lab tours) has been limited, but we have recently been able to restart such activities. We have further communicated our research to non-expert scientists and the general public (e.g. through an article in "Physics Today", social media and the project website).
Our results have been disseminated to the scientific community at international conferences and meetings.
Due to the pandemic and the move of the experiment from Stuttgart to Vienna, participation in outreach activities to promote our research to younger physics and highschool students (e.g. through lab tours) has been limited, but we have recently been able to restart such activities. We have further communicated our research to non-expert scientists and the general public (e.g. through an article in "Physics Today", social media and the project website).
We have investigated the phase diagram of molecular BECs with dipolar interactions and found that molecules are an ideal platform to interpolate between different aspects of supersolidity --- so called droplet supersolids, which have previously been observed in magnetic atoms, and the elusive vacancy-induced supersolids, which are believed to be the mechanism for supersolidity in solid helium. Moreover, we have theoretically investigated the collisional properties of molecules and identified means to realize the tunability of all relevant interactions required to investigate supersolids. Due to these topics being largely unexplored so far, our theoretical contributions have developed into a research direction in its own right, with the ongoing aim to transition from established mean-field models to methods capable to describe strongly-interacting molecules. This work has been part of collaborations including partners in other EU countries, which we expect to lead to coordinated research efforts and joint funding applications are planned for the future. For the molecules, the results set the roadmap for their further cooling to quantum degeneracy and the exploration of supersolids.