News Overview

STRUC­TURES theo­re­ti­cal physicists from the group of Richard Schmidt ( STRUC­TURESInstitute for Theo­re­ti­cal Physics) at Hei­del­berg Uni­ver­si­ty together with experimentalists from the Max Planck Institute of Quan­tum Optics in Garching have made a major breakthrough in the study of atomic Bose-Fermi mixtures. These mixtures are ultracold atomic systems that are composed of both bosonic and fermionic particles and thus enable unique interactions forming new phases of matter. In their study, published in Nature Physics, the re­search team observed first evidence for a quan­tum phase transition from a so-called polaronic to a molecular phase in a density-matched degenerate Bose-Fermi mixture.

This transition, which occurs at low temperatures, is induced by interactions depleting the fraction of bosons that occupy the lowest energy state, and by the build-up of strong correlations. Both result in the emergence of a molecular Fermi gas, which has been theoretically modelled within the group of Prof. Schmidt together with Jonas von Milczewski. The features of the underlying quan­tum phase transition represent a new phenomenon, complementary to the paradigmatic Bose-Einstein condensate/Bardeen–Cooper–Schrieffer crossover observed in Fermi systems. By driving the system through the transition in an experiment by the group of Immanuel Bloch and Xin-Yu Luo in Munich, the researchers have used this novel quan­tum phase transition to produce a record-large sample of sodium-potassium molecules in their absolute ground state exhibiting a large molecule-frame dipole moment in the quantum-degenerate regime.

Further Information and Links:

• Original Publication in Nature Physics: Duda, M., Chen, XY., Schindewolf, A. et al., Nat. Phys. (2023)
• Re­search Briefing: Using a quan­tum phase transition to efficiently produce heteronuclear molecules
• Quan­tum Matter Theory Group - Richard Schmidt