Research for quantum phase transition in quasicrystals

地球上有三种固体：在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。最后一种固体是由2011年诺贝尔化学奖得主谢克特曼于1984年发现的。准晶具有独特的几何结构，如晶体所不具备的旋转对称性，因此有望在准晶中出现独特的电子态。然而，除了广泛的努力外，人们认为准晶中存在的被称为“临界态”的电子结构还没有建立起来。在本研究项目中，我们研究了磁性Au-Al-Yb准晶的低温磁性和热学性质，发现它在零温度附近表现出非常规的量子临界。由此，我们认为这正是准晶所特有的临界态。我们的结果可能为在晶体和准晶的边界附近开辟一条新的研究领域的道路。

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.