Research of quantum phase transitions under high magnetic field using synchrotron x-rays

在这个研究项目中，我们将利用同步辐射x射线的微观技术，如x射线吸收光谱，应用于低温和强磁场中发生的量子相变，以揭示量子临界区的有序参数和电子态。在Ce基重费米子化合物中，我们详细测量了Ce价随磁场的变化，揭示了4f电子的游程如何受到磁场的抑制。在Yb基重费米子化合物中，发现价转变引起YbAgCu4的变磁转变，并且迄今报道的YbRh2Si2中的电子反常并没有伴随着电子结构的大变化，如费米表面重构。

In this research project, we applied microscopic techniques that utilize synchrotron x-rays, such as x-ray absorption spectroscopy, to quantum phase transitions that occur at low temperatures and in high magnetic fields in order to reveal the order parameters and the electronic states in the quantum critical regime. In Ce-based heavy Fermion compounds, we measured the Ce valence as a function of magnetic field in detail and revealed how itinerancy of the 4f electrons is suppressed by magnetic field. In Yb-based heavy Fermion compounds, it was found that a valence transition gives rise to the metamagnetic transition in YbAgCu4 and that the electronic anomalies reported so far in YbRh2Si2 are not accompanied by a large change in electronic structure, such as Fermi surface reconstruction.