Naoya TAJIMA
Senior Research Scientist		  


March 1999 Doctor of Science, Graduate School of Science, The University of Toho


1999-2001 Teaching Assistant, Faculty of Science, Gakushuin University
2001-2003 Special Postdoctoral Researcher, Condensed Molecular Materials Laboratory, RIKEN
2003-2008 Research Scientist, Condensed Molecular Materials Laboratory, RIKEN
2008 to 2011 Senior Research Scientist, Condensed Molecular Materials Laboratory, RIKEN


1. Organic Zero-Gap-Conductor (Massless Dirac Fermions)
      Physical Review Letters, 102(17), 176403/1-176403/4 (2009).
      Europhys. Lett. 80, 47002 (2007).
      J. Phys. Soc. Jpn. Special Issue "Organic Conductors", 75, 051010 (2006).
      J. Phys. IV France 114, 263 (2004).
      Synthetic Metals 133, 95 (2003).
      J. Phys. Soc. Jpn. 71, 1832 (2002).
      Kotai Butsuri, 36，403-412 (2001).
      J. Phys. Soc. Jpn. 69, 543 (2000).

2. Photo-induced Insulator-Metal Transition　
      Kotai Butsuri, 41(2)，119-126 (2006).
      J. Phys. Soc. Jpn. 74, 511 (2005).

3. Magnetotransport Property of Organic Conductors
      J. Phys. Soc. Jpn., 76, 114706 (2007).
      J. Phys. Soc. Jpn. 75, 023705 (2006)
      J. Phys. Soc. Jpn. 75, 053704 (2006).
      Kotai Butsuri, 41(9)，569-582 (2006).
      J. Phys. Soc. Jpn. 72, 1014 (2003).


  1. M. Sato, K. Miura, S. Endo, S. Sugawara, N. Tajima, K. Murata, Y. Nishio, and K. Kajita
    Transport Phenomenon of Multilayer Zero-Gap Conductor in the Quantum Limit
    J. Phys. Soc. Jpn., 80, 023706/1-023706/4 (2011).    New!

  2. K. Hiraki, S. Harada, K. Arai, Y. Takano, T. Takahashi, N. Tajima, R. Kato, and T. Naito
    Local Spin Susceptibility of α-D2I3 (D = bis(ethylendithio)tetraselenafulvalene (BETS) and bis(ethylendithio)dithiadiselenafulvalene (BEDT-STF)) Studied by 77Se NMR
    J. Phys. Soc. Jpn., 80, 014715/1-014715/6 (2011).

  3. S. Sugawara, M. Tamura, N. Tajima, R. Kato, M. Sato, Y. Nishio, and K. Kajita
    Temperature Dependence of Inter-Layer Longitudinal Magnetoresistance in α-(BEDT-TTF)2I3: Positive versus Negative Contributions in a Tilted Dirac Cone System
    J. Phys. Soc. Jpn., 79, 113704/1-113704/4 (2010).

  4. N. Tajima, M. Sato, S. Sugawara, R. Kato, Y. Nishio, and K. Kajita
    Spin and Valley Splittings in Multilayered Massless Dirac Fermion System
    Physical Review B, 82, 121420/1-121420/4 (2010).

  5. R. Kondo, S. Kagoshima, N. Tajima, and R. Kato
    Crystal and electronic structures of the quasi-two-dimensional organic conductor α-(BEDT-TTF)2I3 and its selenium analogue α-(BEDT-TSeF)2I3 under hydrostatic pressure at ROom temperature
    J. Phys. Soc. Jpn., 78(11), 114714/1-114714/7 (2009).

  6. N. Tajima and K. Kajita
    Experimental study of organic zero-gap conductor α-(BEDT-TTF)2I3
    Sci. Technol. Adv. Mater., 10(2), 024308/1-024308/7 (2009).

  7. N. Tajima, S. Sugawara, R. Kato, Y. Nishio, and K. Kajita
    Effect of the zero-mode Landau level on interlayer magnetoresistance in multilayer massless dirac fermion systems
    Phys. Rev. Lett., 102(17), 176403/1-176403/4 (2009).

  8. Y. Kawasugi, H. M. Yamamoto, N. Tajima, T. Fukunaga, K. Tsukagoshi, and R. Kato
    Field-induced carrier delocalization in the strain-induced Mott insulating state of an organic superconductor
    Phys. Rev. Lett., 103(11), 116801/1-116801/4 (2009).   PRL Editors' Suggestions

  9. N. Tajima, R. Kato, and H. Taniguchi
    Transport properties of an organic Mott insulator β'-(BEDT-TTF)2ICl2
    Europhys. Lett., 83, 27008/1-27008/5 (2008).

  10. Y. Kawasugi, H. M. Yamamoto, M. Hosoda, N. Tajima, T. Fukunaga, K. Tsukagoshi, and R. Kato
    Strain-induced superconductor/insulator transition and field effect in a thin single crystal of molecular conductor
    Appl. Phys. Lett., 92, 243508/1-243508/3 (2008).

  11. S. Sugawara, T. Ueno, N. Tajima, Y. Nishio, and K. Kajita
    Magnetoresistance of quasi two-dimensional organic conductors κ(BEDT-TSeF)2FeX4 (X=Cl, Br) and mapping of Fermi surface
    J. Phys. Soc. Jpn., 76(11), 114706/1-114706/7 (2007).

  12. N. Tajima, S. Sugawara, M. Tamura, R. Kato, Y. Nishio and K. Kajita
    Transport properties of massless Dirac fermions in an organic conductor α-(BEDT-TTF)2I3 under pressure
    Europhys. Lett. 80, 47002/1-47002/5 (2007).

  13. K. Takenaka, M. Tamura, N. Tajima, H. Takagi, J. Nohara, and S. Sugai Takenaka et al. Reply:"
    Phys. Rev. Lett 98, 219803 (2007).
    (See also K. Takenaka et al., Phys. Rev. Lett. 95, 227801 (2005).)

  14. J. Fujisawa, N. Tajima, K. Tamaki, M. Shimomura, and T. Ishihara
    Electronic Interactions between Inorganic Nanowires and Organic Electron Acceptors: Drastic Changes in Optical Response and Molecular Vibration
    J. Phys. Chem. C, 111(3), 1146 -1149 (2007).

  15. S. Sugawara, T. Ueno, Y. Kawasugi, N. Tajima, Y. Nishio, and K. Kajita
    Out-of-Plane Resistance under Transverse Magnetic Field in Quasi-One-Dimensional Layered Metals
    J. Phys. Soc. Jpn. 75, 053704 (2006).

  16. N. Tajima, S. Sugawara, M. Tamura, Y. Nishio, and K. Kajita
    Electronic Phases in an Organic Conductor α-(BEDT-TTF)2I3: Ultra Narrow Gap Semiconductor, Superconductor, Metal, and Charge-Ordered Insulator"
    J. Phys. Soc. Jpn. Special Issue "Organic Conductors", 75, 051010 (2006).

  17. R. Jindo, S. Sugawara, N. Tajima, H. M. Yamamoto, R. Kato, Y. Nishio, and K. Kajita
    Out-of-Plane Resistance of Quasi-Two Dimensional Metal (BEDT-TTF)3Cl(DFBIB) in Transverse Magnetic Fields
    J. Phys. Soc. Jpn., 75, 013705 (2006).

  18. K. Takenaka, M. Tamura, N. Tajima, H. Takagi, J. Nohara, and S. Sugai
    Collapse of Coherent Quasiparticle State in θ-(BEDT-TTF)2I3 Observed by Optical Spectoscopy
    Phys. Rev. Lett., 95, 227801 (2005).

  19. J. Fujisawa and N. Tajima
    Photoconductivity Induced by Wire-to-Spacer Charge-Transfer Transitions in an Inorganic-Organic Hybrid Quasi-One-Dimensional Crystal: Polaron Excitation in the Urbach Tail
    Phys. Rev. B, 72, 125201 (2005).

  20. N. Tajima, J. Fujisawa, N. Naka, T. Ishihara, R. Kato, Y. Nishio, and K. Kajita
    Photo-Induced Insulator-Metal Transition in an Organic Conductor α-(BEDT-TTF)2I3
    J. Phys. Soc. Jpn., 74, 511-514 (2005).

  21. N. Tajima, T. Imakubo, R. Kato, Y. Nishio, and K. Kajita
    Uniaxial Strain Effects on Transport Properties of a Supramolecular Organic Conductor θ-(DIETS)2[Au(CN)4]
    J. Phys. Soc. Jpn., 72, 1014-1017 (2003).

  22. M. Fujiwara, N. Tajima, T. Imakubo, M. Tamura, and R. Kato
    Structural and Physical Properties of New Conducting Cation Radical Salts with Te-based Counter Anions, Tetraiodotellurate(II) and Hexaiododitellurate(II)
    J. Solid State Chem., 168, 396-407 (2002).

  23. N. Tajima, A. Ebina-Tajima, M. Tamura, Y. Nishio, and K. Kajita
    Effects of Uniaxial Strain on Transport Properties of Organic Conductor α-(BEDT-TTF)2I3 and Discovery of Superconductivity
    J. Phys. Soc. Jpn., 71, 1832-1835 (2002).

  24. R. Kato, N. Tajima, M. Tamura, and J. Yamaura
    Uniaxial Strain Effect in a Strongly Correlated Two-Dimentional System β'-(CH3)4As[Pd(dmit)2]2
    Phys. Rev. B, 66, 020508(R) (2002).

  25. T. Imakubo, N. Tajima, M. Tamura, R. Kato, Y. Nishio, and K. Kajita
    A Supramolecular Superconductor θ-(DIETS)2[Au(CN)4]
    J. Mater. Chem., 12, 159-161 (2002).

  26. N. Tajima, M. Tamura, Y. Nishio, K. Kajita, and Y. Iye　日本物理学会　第12回論文賞受賞論文
    Transport Property of an Organic Conductor α-(BEDT-TTF)2I3 under High Pressure -- Discovery of a Novel Type of Conductor --
    J. Phys. Soc. Jpn., 69, 543-551 (2000).

  27. J. Yamada, S. Takahashi, M. Kobayashi, N. Tajima, M. Tamura, Y. Nishio, and K. Kajita
    A New Organic Metal Based on the DHTTH Derivativ, (MDHT)2AuI2
    Chem. Lett., 24, 1069-1070 (1995).

  28. T. Ohtsuki, Y. Ono, N. Tajima, and K. Suzuki,
    Equilibrium and Non-Equiribrium Current in the Quantam Hall Regime
    H.A.Cerderia et al.; Quamtum Dynamics of Submicron Structures, 143-150 (1995) Kluwer Academic Publishers. Printed in the Netherlands.



・With Referee Reading
  1. M. Sato, S. Sugawara, N. Tajima, Y. Nishio and K. Kajita
    Transport Property of the Organic Conductor α-(BEDT-STF)2I3in the Magnetic Field
    J. Phys. conf.ser., 132, 012001/1-012001/6 (2008).

  2. K. Katayama, T. Nagai, H. Taniguchi, K. Satoh, N. Tajima, and R. Kato
    High-Pressure Electronic State of κ-(BEDT-TTF)2Cu[N(CN)2]Br Probed by Hall Effect
    J. Phys. Soc. Jpn., 76, 194-195 (2007).

  3. Y. Ishii, N. Tajima, M. Tamura, and R. Kato
    An Interlayer Magnetoresistance Peak Effect below the Superconducting Transition Temperature in Et2Me2P[Pd(dmit)2]2
    J. Low Temperature Physics, 142(3/4), 511-514 (2006).

  4. K. Katayama, T. Nagai, H. Taniguchi, K. Satoh, N. Tajima, and R. Kato
    Anomalous Sign Change in Hall Coefficient of κ-(BEDT-TTF)2Cu[N(CN)2]Br under Pressure
    J. Low Temperature Physics, 142(3/4), 515-518 (2006).

  5. T. Okuhata, T. Nagai, H. Taniguchi, K. Satoh, T. Itou, Y. Shimizu, K. Miyagawa, Y. Ishii, N. Tajima, and R. Kato
    High-Pressure Study of a Doped-Type Organic Superconductor, κ-(BEDT-TTF)4Hg2.89Br8
    J. Low Temperature Physics, 142(3/4), 547-550 (2006).

  6. R. Kato, A. Tajima, A. Nakao, N. Tajima, M. Tamura, and J. Yamaura
    Control of the Electronic State in a Series of Pd(dmit)2 Salts, a Strongly Correlated Elecron System with a Quasi-Triangluar Lattice Structure
    Synth. Met., 153, 397-400 (2005)

  7. R. Kato, N. Tajima, A. Tajima, M. Tamura, and J. Yamaura
    Superconductivity Induced by Uniaxial Strain in the Pd(dmit)2 System
    Synth. Met., 137, 1233-1234 (2003).

  8. T. Imakubo, N. Tajima, T. Shirahata, A. Miyake, H. Sawa, T. Nakamura, H. Ohnuki, M. Tamura, R. Kato, M. Izumi, Y. Nishio, and K. Kajita
    Crystal Design of Organic Conductors Using the Iodine Bond
    Synth. Met., 135-136, 601-602 (2003).

  9. M. Fujiwara, N. Tajima, T. Imakubo, M. Tamura, and R. Kato
    New Te-Based Counter Anions for Conducting Cation Radical Salts --- Tetraiodotellurate(II) and Hexaiododitellurate(II)
    Synth. Met., 133-134, 459-461 (2003).

  10. T. Imakubo, N. Tajima, M. Tamura, R. Kato, Y. Nishio, and K. Kajita
    Supuramolecular Organic Conductor θ-(DIETS)2[Au(CN)4] --- Unique Cristal Structure and Superconductivity under Uniaxial Strain
    Synth. Met., 133-134, 181-183 (2003).

  11. N. Tajima, A. Ebina, M. Tamura, Y. Nishio, and K. Kajita
    Transport Properties of Organic Conductor α-(BEDT-TTF)2I3 and θ-(BEDT-TTF)2I3 under Hydrostatic Pressure or Uniaxial Strain
    Synth. Met., 133-134, 147-149 (2003).

  12. K. Kajita, N. Tajima, A. Ebina, and Y. Nishio
    Organic Semiconductor with Extremle Narrow Energy Gap
    Synth. Met., 133-134, 95-97 (2003).

  13. N. Tajima, A. Ebina, M. Tamura, Y. Nishio, and K. Kajita
    Transport Property of α-(BEDT-TTF)2I3 under High Pressure -- Ultra Narrow Gap Semiconductor
    Synth. Met., 120, 935-936 (2000).

  14. N. Tajima, M. Tamura, Y. Nishio, K. Kajita, and Y. Iye
    Anomalous Magnetotransport of a Highly Mobile Electron System in α-(BEDT-TTF)2I3
    Synth. Met., 103, 1960 (1999).

  15. N. Tajima, M. Tamura, Y. Nishio, K. Kajita, and Y. Iye
    Finding of A New Organic Semiconductor with an Extremely Narrow Gap
    Synth. Met., 103, 1958-1959 (1999).

  16. N. Tajima, M. Tamura, Y. Nishio, K. Kajita, N. Naito, and H. Kobayashi
    Magnetotransport Phenomena of α-(BEDT-TSeF)2I3
    Synth. Met., 86, 1981-1982 (1997).

  17. M. Tamura, F. Matsunaga, N. Tajima, Y. Nishio, and K. Kajita
    Transport Study of an Organic Conductor, θ-(BEDT-TTF)2I3
    Synth. Met., 86, 2007-2008, (1997).

  18. N. Tajima, M. Tamura, Y. Nishio and K. Kajita
    Temperature Independent Conductivity in α-(BEDT-TTF)2I3--- A Novel Mechanism
    Synth. Met., 86, 2005-2006 (1997).


・Without Referee Reading
  1. R. Kato, A. Tajima, A. Nakao, N. Tajima, and M. Tamura
    Correlation and Frustration Effects in Molecular Conductors EtxMe4-xZ[Pd(dmit)2]2 (dmit=C3S52-, Z=P, As, Sb, x=0, 1,2)
    Multifunctional Conducting Molecular Materials, ed. by G. Saito, F. Wudl, R. C. Haddon, K. Tanigaki, T. Enoki, H. E. Katz, and M. Maesato, The Royal Society of Chemistry, Cambridge, UK, 32-38 (2007).
    !Erratum!
    35ページ、Figure 4説明文中の【left】と【right】が逆になっています。
    正しくは、（right; Cation = EtMe3Sb, left; Cation = EtMe3As）です。

  2. R. Kato, A. Tajima, N. Tajima, and M. Tamura
    Electronic States of a Strongly Correlated Two-Dimensional System, Pd(dmit)2 salts, Controlled by Uniaxial Strain and Counter Cations
    J. Phys. IV France 114, 411 (2004).

  3. N. Tajima, A. Tajima, M. Tamura, R. Kato, Y. Nishio, and K. Kajita
    Pressure Control of Transport Property of Organic Conductors; α, θ-(BEDT-TTF)2I3 and θ-(DIETS)2[Au(CN)4]
    J. Phys. IV France, 114, 263 (2004).

  4. N. Tajima, A. Ebina, Y. Nishio, and K. Kajita
    Transport Property of an Organic Conductor α-(BEDT-TTF)2I3 with Ultra Narrow Energy Gap under High Pressures
    Inst. Pure. Applied Phys., "10th International Conference on Narrow Gap Semiconductors", 303 (2001)

  5. K. Kajita, N. Tajima, M. Tamura, and Y.Nishio
    An Ultra Narrow Gap Organic Semiconductor in the Magnetic Field
    4th Int. Symposium on Advanced Physical Fields "Quantum Phenomena in Advanced Materials at High Magetic Fiels" (1999)79



  1. 2009年12月　International Symposium on “Multifunctional Organic Materials and Devices” 2009 (Toho Univ.)
    "Effects of zero-energy Landau level on inter-layer transport in multilayer massless Dirac fermions system"

  2. ISCOM 2009 (Hokkaido,September 2009)
    "Transport property of molecular massless Dirac fermion systems"

  3. ISQM2008 (Tokyo,November 2008)
    "Effects of zero-mode Landau level on transport properties in massless Dirac fermions system α-(BEDT-TTF)2I3"

  4. ISQM-Tokyo'08 (Saitama, August 2008)
    "Transport Properties of Massless Dirac Fermions in an Organic Conductor α-(BEDT-TTF)2I3"

  5. International Symposium on Molecular Conductors (Aichi,July 2008)
    "Transport Properties of Massless Dirac Fermions system α-(BEDT-TTF)2I3"

  6. IXS workshop (Spring-8, February 2006)
    "Electronic Phases in an Organic Conductor α-(BEDT-TTF)2I3"

  7. International Symposium on Molecular Conductors (Hayama, July 2005)
    "Photo-induced Insulator-Metal Transition in an Organic Conductor α-(BEDT-TTF)2I3"

  8. 2003 International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets (France, September 2003)
    "Pressure Control of Transport Property of Organic Conductors; α, θ-(BEDT-TTF)2I3 and θ-(DIETS)2[Au(CN)4]"

  9. 2001 International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets (Hokkaido, September 2001)
    "Organic Semiconductor with Extremle Narrow Energy Gap"



  1. The Young Scientists' Prize, The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology (April 5, 2010)New!
    "Discovery of Molecular Zero-Gap Conductors"

  2. RIKEN Research Incentive Award(March 19, 2009)
    "Discovery of Molecular Zero-Gap Conductors"

  3. JPS 12th Paper Prize (September 23, 2007)
    "Transport Property of an Organic Conductor α-(BEDT-TTF)2I3 under High Pressure -- Discovery of a Novel Type of Conductor --"
    N. Tajima, M. Tamura, Y.Nishio, K.Kajita and Y. Iye; J. Phys. Soc. Jpn., 69, 543-551 (2000).

  4. JPSJ Paper of Editers' Choice (January 15, 2006)
    "Out-of-Plane Resistance of Quasi-Two Dimensional Metal (BEDT-TTF)3Cl(DFBIB) in Transverse Magnetic Fields
    R. Jindo, S. Sugawara, N. Tajima, H. M. Yamamoto, R. Kato, Y. Nishio and K. Kajita; J. Phys. Soc. Jpn. 75, 023705 (2006).

  5. Callenger 21 Award, Ministry of Education, Culture, Sports, Science and Technology (July 2005)

  6. JPSJ Paper of Editers' Choice (February 15, 2005)
    "Photo-Induced Insulator-Metal Transition in an Organic Conductor α-(BEDT-TTF)2I3
    N. Tajima, J. Fujisawa, N. Naka, T. Ishihara, R. Kato, Y. Nishio and K. Kajita; J. Phys. Soc. Jpn. 74, 511 (2005).



  1. 2009.05.07<（The Chemical Daily　7page）
    New! PAPER："Effect of the Zero-Mode Landau Level on Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion Systems"N. Tajima, S. Sugawara, R. Kato, Y. Nishio, and K. KajitaPhysical Review Letters, 102(17), 176403/1-176403/4 (2009).
  2. 2009.04.30（RIKEN press release）
  3. 2005.2.14（RIKEN press release）
  4. 2005.02.15（Science News　front page）
  5. 2005.02.15（The Chemical Daily　11page）
  6. 2005.02.15（The Nikkan Kogyo Shimbun 　29page）
    PAPER:"Photo-Induced Insulator-Metal Transition in an Organic Conductor α-(BEDT-TTF)2I3 ":N.Tajima, J.Fujisawa, N.Naka, T.Ishihara, R.Kato, Y.Nishio and K.Kajita; J. Phys. Soc. Jpn. 74, 511 (2005).





→CMM Member