Recently, the cooperative research team of the Strong Magnetic Field Science Center of the Chinese Academy of Sciences Hefei Institute of Material Science, the University of Science and Technology of China, Fudan University, and the University of Tennessee has used the strong magnetic field and extremely low temperature extreme conditions to study the physical properties of the three-dimensional resistive magnetic material ZnCr2Se4. Make new progress. The team improved the magnetic-temperature phase diagram of ZnCr2Se4 by means of strong magnetic fields, DC/AC magnetic susceptibility at cryogenic temperatures, thermal conductivity, and specific heat, and discovered a magnetic field-induced quantum phase transition. -Driven Quantum Criticality in the Spinel Magnet ZnCr2Se4 was published in the journal Physical Review Letters.
The transition metal oxides, chalcogenites ACr2X4 (A = Zn, Cd, Hg; X = O, S, Se) are a typical type of magnetoresistive frustum system. At low temperatures, these materials have complex magnetic ground states, and Shows the magnetic field-induced fractional magnetization platform, zero-energy mode and other exotic quantum behavior; In addition, with the increase of the applied magnetic field, there is also an undetermined ACCr2X4 system between the helical spin sequence and the completely polarized state. New phase. For this undetermined new phase, two possible explanations have been proposed: the umbrella-like spin state or the spin-liquid crystal phase, both of which will destroy spin-rotational symmetry.
In order to explore the physical nature of this unknown new phase, the team researchers expanded the temperature-field phase diagram of ZnCr2Se4 material through measurement of physical properties under extremely low temperature and strong magnetic fields. The experiment confirmed that the new phase exists between the critical magnetic fields HC2 and HC3. HC2 gradually moves to the high field as the temperature decreases, while HC3 gradually moves to the low field and eventually coincides with a quantum critical point, indicating that the transition from a helical spin sequence to a completely polarized state at absolute zero is a quantum phase transition. The unknown new phase between HC2 and HC3 is the magnetic field-induced quantum critical region (as shown). This quantum critical region has an unusual critical mode that cannot be explained by the simple Ising or Gaussian critical model; Near the quantum critical point (6.5T), the specific heat conforms to the T2 exponential relation at extremely low temperatures, while the heat transfer shows that the mean free path does not change with temperature. This work provides a new idea for resolving the study of quantum critical behavior.
The strong magnetic field center Gu Chuanchuan and China National Chia Sinica Zhao Zhiying co-first author, the strong magnetic field center researcher Yang Zhaorong and China University of Science professor Sun Xuefeng, Fudan University professor Chen Gang and Professor of the University of Tennessee Zhou Haidong as the article co-author.
The above research results have been funded by the National Natural Science Foundation of China and national key R&D projects.