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In the article by Keisuke Natsui et al. (pp. 1943–1949), modulation of a critical current density in heavily boron-doped diamonds is demonstrated by changing the surface termination without introducing any impurity. The critical current density values could be modulated in a reversible manner between the hydrogen- and oxygen-terminated diamonds with maintenance of the superconducting transition temperature. This work demonstrates that changes in the surface termination atoms remarkably affect bulk properties of the superconducting diamond. Moreover, this is the first demonstration of tuning the superconducting properties by a simple process. Generally, when controlling electronic property, it is desirable to reduce the size of host materials to a single-nanometer region because changes in the surface electronic states should be dominant. On the contrary, although the superconducting boron-doped diamonds are about 10 µm thick, superconducting properties could be modulated by only changing the surface termination.