RESEARCH

I have studied the orbital degree of freedom intrinsic in strongly correlated electron systems. Particularly, I focus on the frustration attributed to the anisotropy of orbital states and the dynamical coupling between the orbital and lattice vibration, which will lead to quantum spin liquids.

Fractional excitation is one of the characteristics of quantum spin liquids where long-range orders are not exhibited down to the lowest temperature. The purpose of this study is to investigate Majorana fermionic excitations emerging due to the fractionalization of quantum spins in terms of the topology and clarify the effects on the magnetism and dynamical magnetic response. Moreover, I aim to suggest how to observe Majorana quasiparticles experimentally in quantum spin systems.

EDUCATION

2006

B.Sc. in Physics, Tohoku University

2008

M.S. in Physics, Tohoku University

2011

Ph.D. in Physics, Tohoku University

PROFESSIONAL EXPERIENCE

2008-2010

GCOE Research Assistant, Tohoku University

2010-2011

JSPS Research Fellow

2011-2013

Assistant Professor, Department of Physics, Tohoku Universityy

2013-2014

JSPS Research Fellow(PD)

2014

Assistant Professor, Department of Physics, Tokyo Institute of Technology

2018-Present

Associate Professor, Department of Physics, Yokohama National University

HONORS AND AWARDS

2005

Aoba Society for the Promotion of Science award in Tohoku University

2011

Department of Physics award in Tohoku University

2017

Young Scientist Award of the Physical Society of Japan

2018

The Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan in 2018.

SELECTION OF PUBLICATIONS

"Successive Majorana Topological Transitions Driven by a Magnetic Field in the Kitaev Model"
J. Nasu, Y. Kato, Y. Kamiya, and Y. Motome
Physical Review B 98, 060416(R)-1-6 (Aug. 2018)
DOI: 10.1103/PhysRevB.98.060416

"Thermal Transport in the Kitaev Model"
J. Nasu, J. Yoshitake, and Y. Motome
Physical Review Letters 119, 127204-1-7 (Sep. 2017).
DOI: 10.1103/PhysRevLett.119.127204

"Fermionic response from fractionalization in an insulating two-dimensional magnet"
J. Nasu, J. Knolle, D. L. Kovrizhin, Y. Motome, R. Moessner
Nature Physics 2016 3809-1-5 (Advance online publication in Jul. 2016)
DOI: 10.1038/nphys3809

"Phase diagram and collective excitation in excitonic insulator: from the orbital physics viewpoint"
J. Nasu, T. Watanabe, M. Naka, and S. Ishihara
Physical Review B 93, 205136-1-15 (May. 2016)
DOI: 10.1103/PhysRevB.93.205136

"Thermal fractionalization of quantum spins in a Kitaev model: Temperature-linear specific heat and coherent transport of Majorana fermions"
J. Nasu, M. Udagawa, and Y. Motome
Physical Review B 92, 115122-1-6 (Sep. 2015)
DOI: 10.1103/PhysRevB.92.115122

"Thermodynamics of Chiral Spin Liquids with Abelian and Non-Abelian Anyons"
J. Nasu and Y. Motome:
Physical Review Letters 115, 087203-1-5 (Aug. 2015)
DOI: 10.1103/PhysRevLett.115.087203

"Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal"
N. Katayama, K. Kimura, Y. Han, J. Nasu, N. Drichko, Y. Nakanishi, M. Halim, Y. Ishiguro, R. Satake, E. Nishibori, M. Yoshizawa, T. Nakano, Y. Nozue, Y. Wakabayashi, S. Ishihara, M. Hagiwara, H. Sawa, S. Nakatsuji:
Proceedings of the National Academy of Sciences of the United States of America 112, 9305-9309 (Jul. 2015)
DOI: 10.1073/pnas.1508941112

"Resonating Valence-Bond State in an Orbitally Degenerate Quantum Magnet with Dynamical Jahn-Teller Effect"
J. Nasu and S. Ishihara
Physical Review B 91, 045117-1-8 (Jan. 2015)
DOI: 10.1103/PhysRevB.91.045117

"Vaporization of Kitaev spin liquids"
J. Nasu, M. Udagawa, and Y. Motome
Physical Review Letters 113, 197205-1-5 (Nov. 2014)
DOI: 10.1103/PhysRevLett.113.197205

"Vibronic Excitation Dynamics in Orbitally Degenerate Correlated Electron System"
J. Nasu and S. Ishihara
Physical Review B 88, 205110-1-12 (Nov. 2013)
DOI: 10.1103/PhysRevB.88.205110

"Dynamical Jahn-Teller Effect in a Spin-Orbital Coupled System"
J. Nasu and S. Ishihara
Physical Review B 88, 094408-1-6 (Sep. 2013)
DOI: 10.1103/PhysRevB.88.094408