Research for quantum phase transition in quasicrystals

地球上有三种固体：我们周围无处不在的晶体，像玻璃这样的无定形材料，以及准晶体。最后一种固体是由2011年诺贝尔化学奖得主谢赫特曼在1984年发现的。准晶体具有独特的几何结构，如旋转对称，这是晶体所禁止的，因此有望在它们中出现独特的电子态。然而，除了广泛的努力之外，被认为存在于准晶体中的称为“临界态”的电子结构尚未建立。在本课题中，我们研究了磁性Au-Al-Yb准晶体的低温磁性和热性质，发现它在零温度下表现出非常规的量子临界性。根据这一观察，我们认为这只是准晶体所特有的临界状态。我们的研究结果可能为晶体和准晶体边界附近的一个新的研究领域开辟了道路。

There are three types of solids on this planet: crystals that are ubiquitous around us, amorphous materials like a glass, and quasicrystals. The last type of solids was discovered at 1984 by Schechtman, a Nobel Laureate in Chemistry, 2011. The quasicrystals have unique geometrical structure such as rotational symmetry that is forbidden to crystals, therefore unique electronic states are expected to emerge in them. Besides of extensive efforts, however, the electronic structure called "critical state" that is believed to exist in the quasicrystals is not established yet. In this research project, we studied low-temperature magnetic and thermal properties of the magnetic Au-Al-Yb quasicrystal, and found that it shows unconventional quantum criticality toward zero temperature. From this observation, we suggested that this is just the critical state unique to the quasicrystal. Our results may open a road to a novel research field near the border of the crystal and the quasicrystal.