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The Rigakubu News
The Rigakubu News May. 2026
Advancing Science >

~ Message from a graduate student ~
Manipulating Matter with Light, and Light with Matter

Taiga Nakamoto

Department of Physics , 1st-year Ph.D. student

Place of birth  Chiba, Japan

Undergraduate School: Department of Physics, Faculty of Science, Tohoku University

Apples are red, and the sky is blue. Metals have a luster, and glass is translucent. The color, luster, and transparency of each material are all determined by the interaction between light and the electrons within the material.Furthermore, the bright light emitted by lighting fixtures and displays results from the conversion of the kinetic energy of electrons within materials into light. Fascinated by the principles of this microscopic world woven by light and electrons, I decided to pursue theoretical research in the physics of optical properties.

The true appeal of this field goes beyond simply using light to understand the properties of matter.If we could dramatically change the properties of matter by shining intense light on it (i.e., manipulating matter with light), or if we could rewrite the properties of light by controlling the state of matter (i.e., manipulating light with matter), it would open up entirely new horizons in science.The goal of my research is to find answers to these questions from a microscopic perspective.

On the other hand, it is impossible to directly handle the behavior of the countless electrons within a material as they move while interacting with light. Therefore, I design models that capture the essence behind the phenomena and perform simulations on a computer.It’s rare for a program I’ve written to work on the first try, but the exhilaration I feel when, after much trial and error, an unknown physical phenomenon appears on the screen is irreplaceable. I advance my research day by day, testing new ideas and repeating the cycle of success and failure. Below, I’ll introduce two of the research projects I’ve undertaken.

From the perspective of “manipulating matter with light,” I am studying a special pair state that arises when matter absorbs light.For example, let’s consider an electronic state in which a single electron is packed into each point within a crystal. When light is shone on this state, a pair consisting of a “site packed with two electrons” and a “hole where an electron has been removed” is created (Figure 1-a). This pair resembles an atom—which consists of a pair of a nucleus and an electron—and possesses an interesting structure.
However, this state cannot exist under stable conditions; it appears only when light is shone on the material. Using a measurement technique called “photoelectron spectroscopy,” which examines the electronic states within a material, I theoretically elucidated how this pair state is observed (Fig. 1-b).

From the perspective of “manipulating light with matter,” I am conducting research on extracting light from a “vacuum” by trapping matter between two facing mirrors (Fig. 2-a).In the world of quantum mechanics, even in a vacuum—where nothing is supposed to exist—electromagnetic fields are constantly fluctuating. If we can amplify these fluctuations, it may be possible to extract particles of light from the vacuum.I focused on phase transitions, during which the fluctuations of electrons become amplified, and discovered that when a material is in a state close to a phase transition, the fluctuations in the electromagnetic field are dramatically amplified, causing them to manifest as particles of light (Fig. 2-b). This demonstrates the potential to control light itself from nothing by switching the state of matter.

The two studies introduced above differ not only in their proposed experimental setups but also in the energy scales of light involved. However, the unique appeal of theoretical research lies in the freedom to explore various avenues as long as you have an idea. I hope you, too, will experience the joy of seeing your own ideas come to fruition.

(1)(a) A pair state created by light irradiation. (b) Results obtained when observed using a technique called photoelectron spectroscopy (based on T. Nakamoto et al., arXiv:2603.18982). (2) (a) Electrons confined within a double-mirror system. (b) The number of photons rises dramatically at the phase transition point where the fluctuations of the electrons become larger (based on T. Nakamoto et al., Phys. Rev. B 112, 155150 (2025)).