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Nakata, Koki; Suzuki, Kei
Physical Review Letters, 130(9), p.096702_1 - 096702_6, 2023/03
Times Cited Count：3 Percentile：76.59(Physics, Multidisciplinary)Quantum fluctuations of quantum fields induce a zero-point energy shift under spatial boundary conditions. This quantum phenomenon, called the Casimir effect, has been attracting much attention beyond the hierarchy of energy scales, whereas its application to spintronics has not yet been investigated enough, particularly to ferrimagnetic thin films. Here we fill this gap. Using the lattice field theory, we investigate the Casimir effect induced by quantum fields for magnons and find that the magnonic Casimir effect can arise not only in antiferromagnets but also in ferrimagnets (e.g., YIG). Thus, we pave the way for magnonic Casimir engineering.
Machida, Masahiko; Kato, Koichiro*; Shiga, Motoyuki
Journal of Chemical Physics, 148(10), p.102324_1 - 102324_11, 2018/03
Times Cited Count：19 Percentile：71.35(Chemistry, Physical)The isotopologs of liquid water, H
O, DO, and TO, are studied systematically by first principles PIMD simulations, in which the whole entity of the electrons and nuclei are treated quantum mechanically. The simulation results are in reasonable agreement with available experimental data on isotope effects, in particular, on the peak shift in the radial distributions of HO and DO and the shift in the evaporation energies. It is found that, due to differences in nuclear quantum effects, the H atoms in the OH bonds more easily access the dissociative region up to the hydrogen bond center than the D (T) atoms in the OD (OT) bonds. The accuracy and limitation in the use of the current density-functional-theory-based first principles PIMD simulations are also discussed. It is argued that the inclusion of the dispersion correction or relevant improvements in the density functionals are required for the quantitative estimation of isotope effects.
Shiga, Motoyuki; Takayanagi, Toshiyuki
Chemical Physics Letters, 378(5-6), p.539 - 547, 2003/09
Times Cited Count：7 Percentile：21.52(Chemistry, Physical)no abstracts in English
Mikami, Taiji*; Shiga, Motoyuki; Okazaki, Susumu*
Journal of Chemical Physics, 115(21), p.9797 - 9807, 2001/12
Times Cited Count：27 Percentile：64.09(Chemistry, Physical)no abstracts in English
JAERI-Conf 95-002, 64 Pages, 1995/03
no abstracts in English
Nakata, Koki
no journal, ,
Recently, non-Hermitian quantum mechanics has been attracting considerable attention. The key concepts of quantum mechanics are quantum fluctuations. Quantum fluctuations of quantum fields confined in a finite-size system induce the zero-point energy shift. This quantum phenomenon, the Casimir effect, is one of the most striking phenomena of quantum mechanics in the sense that there are no classical analogs and has been drawing much attention from various research areas, including high energy physics, beyond the hierarchy of energy scales. However, the non-Hermitian extension of the Casimir effect and the application to spintronics remain missing ingredients. Here we fill this gap. By developing a magnonic analog of the Casimir effect into non-Hermitian systems, we show that energy dissipation serves as a key ingredient of Casimir engineering to control and manipulate the Casimir effect of magnons.
