RESEARCH

We have investigated the topological superconducting state in systems with broken spatial inversion symmetry as well as doped topological insulators.

In addition to doped topological insulators (Cu,Sr,Nb)xBi2Se3 （Fig.１）, we will explore various topological quantum phenomena in compounds containing 3d, 4d and 5d transition metal elements and with strong electron correlations, by combining nuclear magnetic resonance (NMR) and materials synthesis techniques. In particular, we will explore the topological superconducting states in the Cr-based compound R₂Cr₃As₃ (T_c=4.8K) and Pt-based locally non-centrosymmetric SrPtAs. In the former, we have found strong ferromagnetic fluctuations and a superconducting gap with point-nodes, which suggests that this material may be a solid analogue of superfluid ³He. On the other hand, SrPtAs shares many similarities with doped graphene in the electronic band structure and the hexagonal crystal structure. In fact, a d+id superconducting state has been proposed theoretically. We will study these compounds in detail by NMR in single crystals.

Fig.１：NMR result showing a broken spin-rotation symmetry in the superconducting state of Cu_xBi₂Se₃（DOI: 10.1038/NPHYS3781）

図2Fig. ２: Crystal structure of Rb₂Cr₃As₃

EDUCATION

1990

Ph.D in Material Physics (Osaka University, Graduate School of Engineering Science)

PROFESSIONAL EXPERIENCE

1990-2004

Assistant Professor, Associate Professor, Osaka University

2004-Present

Professor of Physics, Okayama University

SELECTION OF PUBLICATIONS

"Spin-rotation symmetry breaking in the superconducting state of Cu_xBi₂Se₃"
K. Matano, M. Kriener, K. Segawa, Y. Ando, G.-q. Zheng,
Nature Physics 12, 3781-1-4 (May. 2016).
DOI: 10.1038/nphys3781

"Ferromagnetic spin fluctuation and unconventional superconductivity in Rb₂Cr₃As₃ revealed by ⁷⁵As NMR and NQR."
J. Yang, Z.T. Tang, G.H. Cao and G.-q. Zheng,
Phys. Rev. Lett. 115, 147002-1-5 (Sep. 2015).
DOI: 10.1103/PhysRevLett.115.147002

"Spin-singlet superconductivity with a full gap in locally noncentrosymmetric SrPtAs"
K. Matano, K. Arima, S. Maeda, Y. Nishikubo, K. Kudo, M. Nohara, and G.-q. Zheng,
Phys. Rev. B 89, 140504(R)-1-4 (Apr. 2014).
DOI: 10.1103/PhysRevB.89.140504

"NMR and NQR Studies on Non-centrosymmetric Superconductors Re₇B₃, LaBiPt, and BiPd."
K. Matano, S. Maeda, H. Sawaoka, Y. Muro, T. Takabatake, B. Joshi, S. Ramakrishnan, K. Kawashima, J. Akimitsu, and G.-q. Zheng,
J. Phys. Soc. Jpn. 82, 084711-1-5 (Jul. 2013) (5 pages).
DOI: http://dx.doi.org/10.7566/JPSJ.82.084711

"Abrupt enhancement of noncentrosymmetry and appearance of a spin-triplet superconducting state in Li₂(Pd_1-xPt_x)₃B beyond x=0.8"
S. Harada, J. J. Zhou, Y. G. Yao, Y. Inada, and G.-q. Zheng,
Physical Review B 86, 220502(R)-1-5 (Nov. 2012).
DOI: 10.1103/PhysRevB.86.180501

"Superconducting state in the noncentrosymmetric Mg_9.3Ir₁₉B_16.7 and Mg_10.5Ir₁₉B_17.1 revealed by NMR"
K. Tahara, Z. Li, H. X. Yang, J. L. Luo, S. Kawasaki, and G.-q. Zheng,
Physical Review B 80, 060503(R)-1-4 (Aug. 2009).
DOI: 10.1103/PhysRevB.80.060503

"Spin-singlet superconductivity with multiple gaps in PrO_0.89F_0.11FeAs "
K. Matano, Z.A. Ren, X.L. Dong, L.L. Sun, Z.X. Zhao and G.-q. Zheng,
Europhys. Lett. 83, 57001-1-5 (Sep. 2008).
DOI: 10.1209/0295-5075/83/57001

"Spin Triplet Superconducting State due to Broken Inversion Symmetry in Li₂Pt₃B"
M. Nishiyama, Y. Inada, and G.-q. Zheng,
Phys. Rev. Lett. 98, 047002-1-4 (Jan. 2007).
DOI: 10.1103/PhysRevLett.98.047002

"Field-Induced Ferromagnetic Order and Colossal magnetoresistance in La_1.2Sr_1.8Mn₂O₇:A ¹³⁹La NMR Study"
Y. Shiotani, J.L. Sarrao, and G.-q. Zheng,
Phys. Rev. Lett. 96, 057203-1-4 (Feb. 2006).
DOI: 10.1103/PhysRevLett.96.057203

"Spin singlet pairing in the superconducting state of NaxCoO₂·1.3H₂O: Evidence from a ⁵⁹Co Knight shift in a single crystal"
G.-q. Zheng, K. Matano, D. P. Chen, and C. T. Lin,
Physical Review B 73, 180503(R)-1-4 (May. 2006).
DOI: 10.1103/PhysRevB.73.180503

"Critical point and the nature of the pseudogap of single-layered copper-oxide
Bi₂Sr_2-xLa_xCuO₆ superconductors"
G.-q. Zheng, P.L. Kuhns, A.P. Reyes, B. Liang and C.T. Lin,
Phys. Rev. Lett. 94, 047006-1-4 (Feb. 2005).
DOI: 10.1103/PhysRevLett.94.047006

"Unconventional Superconductivity and Electron Correlations in the Cobalt
Oxyhydrate Na_0.35CoO₂·yH₂O from Nuclear Quadrupole Resonance"
T. Fujimoto, G.-q. Zheng,Y. Kitaoka, R. L. Meng, J. Cmaidalka, and C.W. Chu,
Phys. Rev. Lett. 92, 047004-1-4 (Jan. 2004).
DOI: 10.1103/PhysRevLett.92.047004

"Fermi-Liquid Ground State in the n-Type Pr_0.91LaCe_0.09CuO₄ Copper-Oxide Superconductor"
G.-q. Zheng, T. Sato, Y. Kitaoka, M. Fujita and K. Yamada,
Phys. Rev. Lett. 90, 197005-1-4 (May. 2003).
DOI: 10.1103/PhysRevLett.90.197005

"Gapless Magnetic and Quasi-particles Excitations due to the Coexistence of Antiferromagnetism and Superconductivity in CeRhIn5 : ¹¹⁵In-NQR Study under　Pressure"
S. Kawasaki, T. Mito, Y. Kawasaki, G.-q. Zheng, Y. Kitaoka, D Aoki, Y Haga,
and Y. Onuki,
Phys. Rev. Lett. 91, 137001-1-4 (Sep. 2003).
DOI: 10.1103/PhysRevLett.91.137001

"Unique spin dynamics and unconventional superconductivity in the layered heavy fermion compound CeIrIn5: NQR evidence"
G.-q. Zheng, K. Tanabe, Ts. Mito, S. Kawasaki, Y. Kitaoka, D. Aoki, Y. Haga, and Y. Onuki,
Phys. Rev. Lett. 86, 4664-1-4 (May. 2001).
DOI: 10.1103/PhysRevLett.86.4664