The reporter learned from Nanjing University that an international scientific research team led by Professor Du Lingjie from the School of Physics of the school has made significant progress in the field of quantum physics and observed the "projection" of gravitons in condensed matter for the first time. A related paper was published online in the international academic journal "Nature" on the 28th.

Du Lingjie said that gravitons correspond to gravitational waves, and the latter has been confirmed by experiments, while gravitons have not yet been directly observed. "Gravitons are the product of the combination of general relativity and quantum mechanics. If the existence of this mysterious particle can be confirmed, it may help to unify the two theories, which is of great significance to contemporary physics."

(Left) Quantum metrics describe the shape of orbits. (Right) Orbital deformation produces the lowest energy long-wave excitation. "Nanjing University" WeChat official account picture

He told reporters that in recent years, there have been theoretical predictions that there may be a "fractional quantum Hall effect graviton" in condensed matter. Because its behavior is similar to that of gravitons, it is vividly called the "projection" of gravitons. .

Measurement of graviton excitation by circularly polarized light "Nanjing University" WeChat official account picture

Five years ago, Du Lingjie's team discovered a new collective excitation phenomenon in the fractional quantum Hall effect. The theoretical physics community believes that this may be evidence of the existence of fractional quantum Hall effect gravitons, and has proposed an experimental plan.

"But at that time, there were no measuring equipment that met the experimental requirements at home and abroad. Because this experiment had extremely high requirements for equipment, and it seemed contradictory." Liang Jiehui, co-first author of the paper and a doctoral student at Nanjing University, told reporters that on the one hand, the experiment required Extremely low temperature and strong magnetic field - the temperature is only about 0.05 degrees Celsius higher than absolute zero, and the magnetic field strength must reach more than 100,000 times the earth's average magnetic field. Although these two conditions can be achieved through special refrigerators, on the other hand, in order to carry out For optical measurement, light-transmitting windows must be installed on the refrigerator, which can easily cause the temperature of the experiment to rise, and machine vibration will also affect the accuracy of optical measurement.

The team spent more than three years independently designing, integrating and assembling an experimental device on the campus of Nanjing University. "You can think of it as a two-story microscope." Du Lingjie said that after testing, many measurement parameters of the device have reached the world's leading level.

Relying on this powerful tool, the team successfully observed fractional quantum Hall effect gravitons in gallium arsenide semiconductor quantum wells, and confirmed relevant experimental evidence from three perspectives: spin, momentum, and energy.

"This is the first time that the 'projection' of the graviton concept has been observed in an experiment since it was proposed in the 1930s." Du Lingjie said that the team will continue to study the world of graviton physics in depth, "Looking forward to this 'microscope' Bring us more new discoveries in the quantum frontier."