Imagine an electronic material whose fundamental properties could be changed not by replacing atoms or fabricating new structures, but by applying light, a magnetic field, or an electric signal. A solar cell, for example, could temporarily reshape its energy bands under illumination to harvest light more efficiently.
Such flexibility is not usually possible in conventional semiconductors, where external controls can only change how electrons occupy energy levels rather than the energy band structure itself. Now, a study published in Physical Review B by Chief Researcher Masanori Kohno from MANA demonstrates that strongly correlated insulators such as Mott and Kondo insulators can behave very differently.
In these materials, disturbing spins or charges via doping (addition of holes or electrons through a chemical-potential shift), magnetization, or light can induce entirely new electronic states inside the gap between energy bands. This occurs because electrons interact strongly with one another. Unlike ordinary band insulators, where spin and charge excitations are tightly linked, correlated insulators allow low-energy spin excitations to exist independently.
By theoretical analyses and numerical calculations, this study elucidates how spin and charge perturbations affect the band structures of these insulators, clarifying the microscopic mechanism responsible for the emergence of these electronic modes. The results show that when a large collective number of spins or charges are excited, the induced states can have significant intensity, reshaping the electronic band structure.
“This research shows that, unlike conventional semiconductors, spin and charge perturbations can create new electronic modes that actively modify band structures,” says Dr. Kohno.
The findings could lay the groundwork for band-structure engineering based on strong electron correlations, enabling future electronic and optoelectronic devices with enhanced and tunable functionality.
Research Highlights Vol. 95
https://www.nims.go.jp/mana/research/researchactivities/highlights/vol95.html
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Reference
Source: Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS)
DOI: https://doi.org/10.1103/ythd-s2x8
About Research Center for Materials Nanoarchitectonics (MANA)
The Research Center for Materials Nanoarchitectonics (MANA) is one of the core research centers of the National Institute for Materials Science (NIMS). Established in 2007 under the World Premier International Research Center Initiative (WPI) by Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT), MANA pioneers the concept of Nanoarchitectonics to design innovative materials at the nanoscale level. MANA promotes world-class research, fosters global collaboration, and supports the development of young scientists. With a strong international presence and interdisciplinary approach, MANA continues to lead in advancing materials science for a more sustainable and innovative future.
Website: https://www.nims.go.jp/mana/index.html
MANA Research Highlights
MANA independently selects and publishes its exceptional research achievements as “Research Highlights,” which are different from the official ‘Press releases’ disseminated by NIMS, with the purpose of showcasing its research outcomes.
https://www.nims.go.jp/mana/research/researchactivities/highlights/index.html
About the World Premier International Research Center Initiative (WPI)
The WPI was launched in 2007 by Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT), to foster globally visible research centers exhibiting the highest standards and outstanding research environments. With over a dozen centers that operate at several institutions throughout the country, these centers are given a high degree of autonomy, allowing them to pursue innovative modes of management and research. This program is supported by the Japan Society for the Promotion of Science (JSPS).
See the latest research news from the centers at the:
WPI News Portal: https://www.eurekalert.org/newsportal/WPI
WPI program website: https://www.jsps.go.jp/english/e-toplevel/index.html
Physical Review B
Electronic modes induced by spin and charge perturbations in Mott and Kondo insulators
3-Dec-2025