1980.4-1984.3 The University of Tokyo
1984.4-1987.2 Graduate School of Science, The University of Tokyo
1987.3-1992.3 Research Associate, Department of Physics, The University of Tokyo
1992.4-2002.3 Associate Prof., The Institute for Solid State Physics, The University of Tokyo
2002.4-2007.8 Associate Prof., Department of Physics, The University of Tokyo
2007- Professor, Department of Physics, The University of Tokyo

Research Field:
Condensed Matter Physics Theory, Computational Physics, Materials Science, Surface Science

Award:
2001.11 Japan IBM Science Prize in Physics
2024.5 21^st Honda Frontier Award

Recent Research Highlights (2012-2019)

Computer simulations from first principles enable us to investigate properties and behavior of materials beyond the limits of experiments. Our main subject is to develop and apply such methods to explain the physics of materials, to predict material properties, and to create new materials.

1. Development of the transcorrelated method for condensed matter
   The transcorrelated (TC) method, initially proposed by S. F. Boys and N. C. Handy more than 40 years ago but forgotten until recently, is a wave function theory for first-principles electronic structure calculation with explicitly correlated wave functions. We noticed its conceptual and practical importance and have been trying to establish the method for an alternative of the density functional theory for years. In 2006, we reported the first application of the TC method to the band structure calculation, but there was a severe problem of the computational cost. After 2012, we developed new algorithms to speed up the calculation drastically and realized its application to various materials and extended the method for the calculation of electronic excitation spectra also. We showed that the electronic band structure of ZnO is reproduced best among the first-principles methods reported so far [1].
2. Development of the first-principles simulation of the thermal properties of crystals.
   For the simulation of the thermal properties of crystals, a precise calculation of the anharmonic phonon effect is necessary. A problem there is that the spatiotemporal scale of phonon properties is diverse. So it is not easy to simulate them by the simple application of the first-principles simulation. We developed a method to combine first-principles molecular dynamics with so-called sparse modeling, and established reliable calculation of the thermal conductivity of crystals [2]. We also introduced the self-consistent phonon approach to calculate soft phonon modes of high-temperature/high-symmetry phases realized by the thermal fluctuation of atoms with a modest computational cost. We applied these methods to clarify the mechanism of extremely low thermal conductivity in a clathrate [3]. Our code (ALAMODE) is open for the public and used by researchers in the academy and also in industry.
3. Development of the Superconducting DFT code and its application to hydrogen sulfide at high pressure
   In 2015, hydrogen sulfide made a record of the superconducting transition temperature (Tc) at high pressure. The surprisingly high Tc above 200K is explained by the phonon mechanism, on which we have contributed by the world's first calculation of the accurate Tc with the superconducting density functional theory (SCDFT) [4]. In this study, we used an in-house SCDFT code we developed, for which we had made an efficient method for the Brillouin-zone integration to improve the convergence of the calculation.
4. Development of the data assimilation method to predict crystal structures
   Theoretical prediction of crystal structures from its chemical composition and physical conditions has been a long-standing problem of physical sciences. Although there have been so many successful researches on the structural search algorithms, the number of atoms in the unit cell reachable with these algorithms is limited. We made a method to assimilate powder diffraction data in the structure simulation [5]. We showed the search of complicated crystal structures are highly accelerated even if the diffraction data is incomplete due to the experimental constraints or the problem of the quality of the sample. The method will support structure determination in, for example, high-pressure experiments or materials development.
5. Non-thermal laser ablation of metals by a femtosecond laser
   Femtosecond laser irradiation on a metal surface changes the electron subsystem and causes ablation without apparent thermal damage to the surrounding area. We often call this phenomenon a non-thermal ablation, but its physical mechanism is unclear. Based on the first-principles calculation of an electronically high-temperature system, we proposed the electronic entropy-driven mechanism for the Ʈon-thermalǠablation. We developed a simple simulation model for ablation and succeeded in the reproduction of the ablation depth of Copper as a function of the laser-fluence [6].

[1] M. Ochi, et al., Correlated Band Structure of a Transition Metal Oxide ZnO Obtained from a Many-Body Wave Function Theory, Phys. Rev. Lett. 118, 026402 (2017).
[2] T. Tadano, et al., Anharmonic force constants extracted from first-principles molecular dynamics: applications to heat transfer simulations, J. Phys.: Condens. Matter 26, 225402 (2014).
[3] T. Tadano, et al., Impact of Rattlers on Thermal Conductivity of a Thermoelectric Clathrate: A First-Principles Study, Phys. Rev. Lett. 114, 095501 (2015).
[4] R. Akashi et al., First-principles study of the pressure and crystal-structure dependences of the superconducting transition temperature in compressed sulfur hydrides, Phys. Rev. B 91, 224513 (2015).
[5] N. Tsujimoto, D. Adachi, R. Akashi, S. Todo, and S. Tsuneyuki, Crystal structure prediction supported by incomplete experimental data, Phys. Rev. Materials 2, 053801 (2018).
[6] Y. Tanaka and S. Tsuneyuki, Possible electronic entropy-driven mechanism for non-thermal ablation of metals, Appl. Phys. Express 11, 046701 (2018).

 Recent Papers

Methods for first-principles electronic structure calculation

• T. Amano, T. Yamazaki, R. Akashi, T. Tadano, S. Tsuneyuki, Lattice dielectric properties of rutile TiO₂: First-principles anharmonic self-consistent phonon study, Phys. Rev. B, 107, 094305 (2023).
• S. Yoshikawa, R. Sato, R. Akashi, S. Todo, S. Tsuneyuki, A noise-robust data assimilation method for crystal structure determination using powder diffraction intensity, J. Chem. Phys. 157, 224112 (2022)
• Yuansheng Zhao Ryuhei Sato and Shinji Tsuneyuki, Accelerating simulated annealing of glassy materials with data assimilation, J. Non-Cryst. Solids 600, 122028 (2022).
• Cristian M. Le, Ryosuke Akashi, Shinji Tsuneyuki, The missing quantum number of the Floquet states, Phys. Rev. A 105, 052213 (2022)
• D. Adachi, N. Tsujimoto, R. Akashi, S. Todo and S. Tsuneyuki, Search for common minima in joint optimization of multiple cost functions, Comput. Phys. Commun. 241, 92-97 (2019)
• N. Tsujimoto, D. Adachi, R. Akashi, S. Todo, and S. Tsuneyuki, Crystal structure prediction supported by incomplete experimental data, Phys. Rev. Materials 2, 053801 (2018).
• S. Yamada, F. Shimojo, R. Akashi, and S. Tsuneyuki, Efficient method for calculating spatially extended electronic states of large systems with a divide-and-conquer approach, Phys. Rev. B 95, 045106 (2017).
• M. Ochi, R. Arita, and S. Tsuneyuki, Correlated Band Structure of a Transition Metal Oxide ZnO Obtained from a Many-Body Wave Function Theory, Phys. Rev. Lett. 118, 026402 (2017).
• M. Ochi, Y. Yamamoto, R. Arita and S. Tsuneyuki, Iterative diagonalization of the non-Hermitian transcorrelated Hamiltonian using a plane-wave basis set: Application to sp-electron systems with deep core state, J. Chem. Phys. 144, 4109 (2016).
• M. Ochi and S. Tsuneyuki, Second-order Moller-Plesset perturbation theory for the transcorrelated Hamiltonian applied to solid-state calculations, Chem. Phys. Lett. 621, 177-183 (2015).
• M. Ochi, K.Sodeyama and S. Tsuneyuki, Optimization of the Jastrow factor using the random-phase approximation and a similarity-transformed Hamiltonian: Application to band-structure calculation for some semiconductors and insulators, J. Chem. Phys. 140, 074112-1-12 (2014).
• M. Ochi and S. Tsuneyuki, Optical Absorption Spectra Calculated from a First-Principles Wave Function Theory for Solids: Transcorrelated Method Combined with Configuration Interaction Singles, J. Chem. Theo. Comp. 10, 4098-4103 (2014).
• M. Kawamura, Y. Gohda and S. Tsuneyuki, Improved tetrahedron method for the Brillouin-zone integration applicable to response functions, Phys. Rev. B89, 094515 (2014).
• T. Kobori, K. Sodeyama, T. Otsuka, Y. Tateyama and S. Tsuneyuki, Trimer Effects in Fragment Molecular Orbital-Linear Combination of Molecular Orbitals Calculation of One-Electron Orbitals for Biomolecules, J. Chem. Phys., 139, 094113 (2013).
• M. Ochi, K. Sodeyama, R. Sakuma and S. Tsuneyuki, Efficient algorithm of the transcorrelated method for periodic systems, J. Chem. Phys. 136, 094108(2012).

Superconductivity

• T Ishikawa, Y Tanaka and S Tsuneyuki, Evolutionary search for superconducting phases in the lanthanum-nitrogen-hydrogen system with universal neural network potential, Phys. Rev. B 109, 094106, (2024) .
• K Tsutsumi, Y Hizume, M Kawamura, R Akashi, S Tsuneyuki, Effect of spin fluctuations on superconductivity in V and Nb: A first-principles study, Phys. Rev. B 102 (21), 214515 (2020).
• M. Kawamura, R. Akashi and S. Tsuneyuki, Anisotropic superconducting gaps in YNi2B2C: A first-principles investigation, Phys. Rev. B 95, 4506 (2017).
• R. Akashi, W. Sano, R. Arita, and S. Tsuneyuki, Possible ȍagneliɠPhases and Self-Alloying in the Superconducting Sulfur Hydride, Phys. Rev. Lett. 117, 075503 (2016). Editor's Suggestion
• R. Akashi, M. Kawamura, S. Tsuneyuki, Y. Nomura, R. Arita, First-principles study of the pressure and crystal-structure dependences of the superconducting transition temperature in compressed sulfur hydrides, Phys. Rev. B 91, 224513 (2015).

Thermal properties

• M. Ohnishi, T. Tadano, S. Tsuneyuki, J. Shiomi, Anharmonic phonon renormalization and thermal transport in the type-I Ba8Ga16Sn30 clathrate from first principles, Phys. Rev. B 106, 024303 (2022).
• Y. Oba, T. Tadano, R. Akashi and S. Tsuneyuki, First-principles study of phonon anharmonicity and negative thermal expansion in ScF₃, Phys. Rev. Materials 3, 033601-1-11 (2019).
• T. Tadano and S. Tsuneyuki, Quartic Anharmonicity of Rattlers and Its Effect on Lattice Thermal Conductivity of Clathrates from First Principles, Phys. Rev. Lett., 120, 105901-1-6 (2018).
• T. Tadano and S. Tsuneyuki, First-Principles Lattice Dynamics Method for Strongly Anharmonic Crystals, J. Phys. Soc. Japan 87, 041015 (2018).
• T. Tadano and S. Tsuneyuki, Self-consistent phonon calculations of lattice dynamical properties in cubic SrTiO₃ with first-principles anharmonic force constatns, Phys Rev. B 92, 054301 (2015).
• T. Tadano, Y. Gohda, and S. Tsuneyuki, Impact of Rattlers on Thermal Conductivity of a Thermoelectric Clathrate: A First-Principles Study, Phys. Rev. Lett. 114, 095501 (2015).
• T. Tadano, Y. Gohda, and S. Tsuneyuki, Anharmonic force constants extracted from first-principles molecular dynamics: applications to heat transfer simulations, J. Phys.: Condens. Matter 26, 225402 (2014).

Photoexcitation and laser ablation

• Cristian M. Le, Ryosuke Akashi, Shinji Tsuneyuki, The missing quantum number of the Floquet states, Phys. Rev. A 105, 052213 (2022)
• H. Katow, R. Akashi, Y. Miyamoto, S. Tsuneyuki, First Principles Study of the Optical Dipole Trap for Two-Dimensional Excitons in Graphane, Phys. Rev. Lett. 129, 047401 (2022).
• Y. Tanaka and S. Tsuneyuki, Possible electronic entropy-driven mechanism for non-thermal ablation of metals, Appl. Phys. Express 11, 046701-1-4 (2018) (Spotlights 2018)
• H. Katow, J. Usukura, R. Akashi, K. Varga and S. Tsuneyuki, Numerical investigation of triexciton stabilization in diamond with multiple valleys and bands, Phys. Rev. B95, 125205 (2017).

Dielectric materials and impurities

• J. Tsuchiya, M. Shiga, S. Tsuneyuki, E.C. Thompson, Nuclear quantum effect on the elasticity of ice VII under pressure: A path-integral molecular dynamics study, Phys. Rev. Research 6 (2), 023302 (2024).
• N. Sato, R. Akashi, and S. Tsuneyuki, Universal two-dimensional characteristics in perovskite-type oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs) , J. Chem. Phys., 147,034507(2017) .
• N. Sato and S. Tsuneyuki, Perovskite-type oxyhydride with a two-dimensional electron system: First-principles prediction of KTiO₂H, Appl. Phys. Lett. 109, 172903 (2016).
• Y. Iwazaki, Y. Gohda and S. Tsuneyuki, Diversity of hydrogen configuration and its roles in SrTiO_{3-delta}, APL Mat. 2, 012103 (2014).
• Y. Iwazaki, T. Suzuki, Y. Mizuno and S. Tsuneyuki, Doping-induced phase transitions in ferroelectric BaTiO3 from first-principles calculations, Phys. Rev. B86, 214103(2012).

Magnetic materials

• T. Ishikawa, R. Akashi, K. Kubo, Y. Toga, K. Inukai, I. Rittaporn, M. Hayashi, and S. Tsuneyuki, Large intrinsic spin Hall conductivity in orthorhombic tungsten, Phys. Rev. Materials 7, 026202 (2023).
• Yuki K. Wakabayashi, Yoshiharu Krockenberger, Naoto Tsujimoto, Tommy Boykin, Shinji Tsuneyuki, Yoshitaka Taniyasu and Hideki Yamamoto, Ferromagnetism above 1000 K in a highly cation-ordered double-perovskite insulator Sr₃OsO₆, Nature Communications 10, 535 (2019).
• Y. Tatetsu, S. Tsuneyuki, and Y. Gohda, First-principles study on substitution effects in Nd₂(Fe, X)₁₄B, Materialia 4, 388-394 (2018).
• Y. Tatetsu, S. Tsuneyuki, and Y. Gohda, First-Principles Study of the Role of Cu in Improving the Coercivity of Nd-Fe-B Permanent Magnets, Phys. Rev. Applied 6, 064029 (2016).
• Z. Torbatian, T. Ozaki, S. Tsuneyuki and Y. Gohda, Strain effect on the magnetic anisotropy of Y2Fe14B examined by first-principles calculations, Appl. Phys. Lett. 104, 242403-1-4 (2014).

Surface and Interface

• Y. Gohda, Y. Tatetsu, and S. Tsuneyuki, Electron theory on grain-boundary structures and local magnetic properties of neodymium magnets, Mater. Trans., 59, 332 (2018).
• Y. Ando, Y. Gohda and S. Tsuneyuki, Dependence of the Schottky barrier on the work function at metal/SiON/SiC(0001) interfaces identified by first-principles calculations, Surf. Sci. 606, 1501(2012)
• Y. Ando, Y. gohda and S. Tsuneyuki, Ab initio molecular dynamics study of the Helmholtz layer formed on solid?liquid interfaces and its capacitance, Chem. Phys. Lett. 556, 9-12 (2012).
• Y. Gohda and S. Tsuneyuki, Structural Phase Transition of Graphene Caused by GaN Epitaxy, Appl. Phys. Lett. 100, 053111-1-4 (2012).
• Y. Gohda and S. Tsuneyuki, Two-dimensional intrinsic ferromagnetism at nitride-boride interfaces, Phys. Rev. Lett. 106, 047201 (2011).