"An example of curiosity-driven research." — Professor Mikio Kozuma
Direct Observation of the Einstein-de Haas Effect
A team led by Professor Mikio Kozuma, along with Specially Appointed Assistant Professors Hiroki Matsui and Yuki Miyazawa, has reported the first direct observation of the Einstein-de Haas effect in a Bose-Einstein condensate (BEC) of europium atoms.
Background
The Einstein-de Haas effect, first proposed in 1915 by Albert Einstein and Wander Johannes de Haas, describes the rotation of an object that occurs when the spin of its constituent atoms is altered. This is a result of the conservation of angular momentum. Previous attempts to study this effect in solid materials were hindered by noise from atomic vibrations and impurities.
Methodology
The team cooled europium atoms into a BEC, a state where atoms behave coherently as a wave. External magnetic fields were reduced to near zero, and the condensate was observed using an interferometer.
Observation
The researchers observed that atoms with changed spins formed a ring-shaped distribution. Analysis of phase shifts confirmed that the condensate was rotating.
Significance
This experiment demonstrates the conversion of spin to rotation in an ultra-low-noise environment, allowing for a more detailed study of the quantum effect.
Theoretical Link Established in Spin Glass Dynamics
In a separate study, a research team led by Specially Appointed Professor Hidetoshi Nishimori has theoretically demonstrated a fundamental connection between two previously separate phenomena in spin glasses.
Background
Spin glasses are a class of materials in which atomic magnets (spins) do not align in an orderly state at low temperatures due to impurities. Over fifty years of study have identified two counterintuitive phenomena: the reentrant transition, where cooling the system destroys order rather than creates it, and temperature chaos, where a tiny temperature variation causes a significant change in the system's state.
Methodology
The team developed a new theoretical model that allowed for precise control over impurity interactions. Their mathematical analysis indicates that if a reentrant transition occurs, temperature chaos must follow as a logical consequence.
Significance
This finding establishes a new path for theory-based prediction in complex systems. The detection of a reentrant transition now enables the prediction of subsequent temperature chaos in spin glasses.
Applications
The research team states that the relationship is also valid under conditions that more closely resemble real materials. Spin glass theory has relevance to other complex problems, including optimization tasks, reasoning processes in artificial intelligence, and studies on the spread of infectious diseases.