My field of expertise is condensed matter physics, and I am engaged in the theoretical research of the properties of solids. I am particularly interested in structures known as ‘quasicrystals.’ Solids are comprised of large numbers of atoms, and solids in which these atoms are arranged in a periodic manner are called ‘crystals.’ Quasicrystals are another kind of solid in that their atoms are arranged in a non-periodic manner.

Atoms are made up of positively charged nuclei negatively charged electrons. Electrons move around at some distance from the nuclei, and the way these electrons move largely determines the properties of a substance. If the arrangement of atoms in a solid changes, then the movement of its electrons changes—and, as a result, the properties of the solid also change.

Imagine a town in which all the roads cross each other at right angles in a grid pattern—cars can travel through such a town with ease; but if a town is a tangle of curved roads, then cars can only move with difficulty. This is similar to how electrons flow.

I use computer simulations to analyze how changes in the regularity of atom arrangements result in changes in the movement of electrons; and, in so doing, I attempt to discover new properties in these substances.

Hints of novel solid structures to be found all around us

In my research, I am also involved in applying the concept of hyperuniform structures to solid state physics. In a hyperuniform structure, even if atoms are arranged irregularly, atoms are distributed evenly as a whole with a less spatial fluctuation in the density.

Hyperuniform structures exist all around us. Examples include photoreceptor cells in the retinas of birds with outstanding eyesight, and the distribution of looped veins in plant leaves. It is thought that evolutionary pressures have favored structures with minimal fluctuations in density.

I discovered that the distribution of electrons within quasicrystals is hyperuniform. In quasicrystals, electrons are distributed in unusual patterns; and I found that the framework of hyperuniformity is useful for characterizing these distributions, too.

How electrons are distributed in a quasicrystal influences its properties. As such, I believe that actively utilizing changes in these patterns, we might uncover a new way to control substance’s properties. I am trying to apply the framework of hyperuniformity to other types of solid, too, including amorphous solids.

Introducing the concept of quasicrystal structures to superconductivity and to magnets

I rely on the cooperation of experimental researchers to detect and prove the results of my computer simulations in actual substances. I am therefore actively engaged in joint research with researchers from various disciplines. In the field of solid-state physics, few physicists are involved in researching non-crystalline solids, and so many of the most fundamental aspects remain unexplored—I find it to be very rewarding.

I also research superconductivity and magnetism. Combining these fields with the fields of quasicrystals and of disordered hyperuniform structures further expands the scope of my research. I want to convey to my students how interesting it can be to research unexplored fields.

Since I am also involved in joint research with many labs both in Japan and overseas, I would like to create opportunities for my students to carry out extended research overseas. This would allow them to interact with people from various countries and universities, and expose them to diverse ways of thinking.

The book I recommend

“The Second Kind of Impossible”
by Paul J. Steinhardt, Japanese translation by Takao Saito, Misuzu Shobo

Paul J. Steinhardt is a theoretical physicist who came up with the concept of quasicrystals. The book chronicles Steinhardt’s and his friends’ journeys around the world in their attempts to answer the question of whether quasicrystals exist in the natural world. The plot is thrilling, much like a mystery novel—it fully conveys how exciting research can be.

Interviewed: June 2025