Berkeley Lab observes tunable exciton Bose-Einstein condensate switchable by magnets

A team led by Lawrence Berkeley National Laboratory has observed a tunable Bose-Einstein condensate of excitons in an atomically thin semiconductor and found the condensate's internal structure can be switched with a magnetic field, phys.org reported, citing a Nature study. Bose-Einstein condensates are a quantum state in which many particles behave as one collective object. Creating them from excitons-electron-hole pairs-in solid devices has been hard because optically generated excitons last only about a billionth of a second. The researchers engineered a 2D semiconducting device with ground-state excitons, used magneto-optical spectroscopy near absolute zero, and reported condensate signatures that persisted up to about 2 kelvins. Principal investigator Feng Wang said prior work lacked an easy way to tell whether excitons formed a condensate or what internal quantum order it had. Co-author Ruishi Qi said a small magnetic field can switch the same exciton fluid's internal structures. phys.org linked the platform to quantum simulations, optoelectronics, and exciton-based devices. DOI: 10.1038/s41586-026-10636-y.