Researchers at Berkeley Lab have achieved a significant milestone in quantum physics by observing a tunable Bose-Einstein condensate of excitons within an atomically thin semiconductor. This development offers a new approach to studying quantum fluids in solid materials, moving away from the traditional, highly difficult methods using supercold gasses in a vacuum.
For decades, scientists worked to create these condensates using electron-hole pairs known as excitons. In past attempts, these particles proved difficult to control because they existed only for a billionth of a second after being generated by light. By engineering a 2D semiconducting device, the team successfully created excitons in their ground state. This allows the particles to reach equilibrium and remain stable for study.
The research reveals that this condensate is more complex than previously thought. It contains multiple internal spin-valley structures that function like different flavors. Researchers can switch these structures using a magnetic field. This discovery effectively turns the condensate into a controllable platform for future applications, including high-speed optoelectronics and next-generation quantum computing.
The team conducted their experiments at temperatures near absolute zero, though they observed the condensate signatures persisting up to 2 Kelvin. While still very cold, this is a notable improvement over standard atomic gas demonstrations. The ability to tune the density of these excitons electrically adds another layer of precision to the experimental setup.
This work involved collaboration across several institutions, including UC Berkeley and the University of Texas at Austin. By providing direct access to the hidden internal order of quantum fluids, this study sets the stage for the creation of new superfluid-based circuits and simulation tools. The findings appear in the journal Nature, marking a shift in how we might handle macroscopic quantum coherence in solid-state devices.