The research team made significant advances in experimental studies of localization phase transitions in interacting Bose gases. Their findings were published in Physical Review Letters under the title “Observation of interaction-induced mobility edge in an atomic Aubry-André wire.” The paper was highlighted as an Editors’ Suggestion and featured on the journal’s homepage. Additionally, Physics magazine published a spotlight article titled “A Wire on the Edge” by Professor Martin Rodriguez-Vega to discuss the study's key insights.

The research team has successfully synthesized a one-dimensional momentum lattice in an ultracold Bose quantum gas with tunable interactions. By introducing a quasiperiodic disordered potential, they observed Anderson localization transitions dependent on the system’s eigenenergy, demonstrating an interaction-tunable mobility edge. Using a broad Feshbach resonance, the researchers controlled the sign of interatomic interactions and adjusted parameters of the momentum lattice and quasiperiodic potential. This enabled the adiabatic preparation of the system's highest excited state via the ground state of a negative Hamiltonian.

The study explored how interactions affect Anderson localization dynamics across different eigenstates. For the ground state, repulsive interactions accelerated the transition from extended to localized phases, while attractive interactions delayed the localization transition. Conversely, for the system’s highest excited state, the impact of interactions on localization was reversed. The team identified critical quasiperiodic disorder strengths for extended-localized transitions across various eigenstates as functions of interaction strength, constructing a phase diagram of the mobility edge. The experimental results align with the predictions of the nonlinear quasiperiodic Aubry-André (AA) model.

The momentum lattice based on interacting ultracold Bose atomic quantum gases serves as an ideal experimental platform for investigating Anderson localization and mobility edges in quasiperiodic disordered potentials. The findings advance our understanding of novel physical phenomena arising from the interplay of interactions and disorder, offering valuable insights for achieving interaction-controlled quantum transport and quantum phase transitions in disordered systems in the future.

Ph.D. candidate Yunfei Wang is the first author of the paper. Associate Professor Yuqing Li, Professors Feng Mei, Ying Hu, and Jie Ma are corresponding authors. Doctoral candidate Jiahui Zhang, Professors Jizhou Wu, Lecturer Wenliang Liu, Professor Liantuan Xiao, and Professor Cheng Chin from the University of Chicago contributed to this research.

This work was supported by the National Key R&D Program, the NSFC Key International Cooperation Project, and NSFC General Research Programs.

Link to the paper: https://link.aps.org/doi/10.1103/PhysRevLett.129.103401