Scientists at NIST and the Joint Quantum Institute have discovered that dark solitons in ultracold quantum fluids behave differently when impurities are present. These impurities, which retain their classical billiard-ball behavior, interact with the dark soliton like a heavy particle colliding with lightweight impurities. This causes the soliton to accelerate rather than slow down, exceeding its speed limit and destabilizing into sound waves.
The researchers found that treating the dark soliton as having negative mass provided the correct mathematical framework to explain this behavior. This discovery could help clarify the boundary between classical and quantum physics, and may also shed light on similar phenomena in optical fibers where noise disrupts precise timing for long-distance communication.
Source: https://www.nist.gov/news-events/news/2017/02/mystery-dark-solitons
Keywords: soliton, quantum fluid, ultracold atoms, negative mass
