Article | Published:

Superconductivity in CuxTiSe2


Charge density waves (CDWs) are periodic modulations of the density of conduction electrons in solids. They are collective states that arise from intrinsic instabilities often present in low-dimensional electronic systems. The most well-studied examples are the layered dichalcogenides–an example of which is TiSe2, one of the first CDW-bearing materials to be discovered. At low temperatures, a widely held belief is that the CDW competes with another collective electronic state, superconductivity. But despite much exploration, a detailed study of this competition is lacking. Here we report how, on controlled intercalation of TiSe2 with Cu to yield CuxTiSe2, the CDW transition can be continuously suppressed, and a new superconducting state emerges near x=0.04, with a maximum transition temperature Tc of 4.15 K at x=0.08. CuxTiSe2 thus provides the first opportunity to study the CDW to superconductivity transition in detail through an easily controllable chemical parameter, and will provide fundamental insight into the behaviour of correlated electron systems.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Wilson, J. A. & Yoffe, A. D. The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties. Adv. Phys. 28, 193–335 (1969).

  2. 2

    Wilson, J. A., Di Salvo, F. J. & Mahajan, S. Charge-density waves and superlattices in the metallic layered transition metal diehaleogenides. Adv. Phys. 24, 117–201 (1975).

  3. 3

    Di Salvo, F. J., Moncton, D. E. & Waszczak, J. V. Electronic properties and superlattice formation in the semimetal TiSe2 . Phys. Rev. B 14, 4321–4328 (1976).

  4. 4

    Kim, S. J. et al. AFM image visualization of layered dichalcogenides, 1T-MTe(2) (M=V, Ta). J. Phys. Chem. Solids 58, 659–663 (1997).

  5. 5

    Kasuya, T., Jung, M. H. & Takabatake, T. Charge density wave and excitonic magnetic polarons in CeTe2 . J. Magn. Magn. Mater. 220, 235–258 (2000).

  6. 6

    Boswell, F. W. & Bennett, J. C. Density waves in Nb3Te4: Effects of indium and thallium intercalation. Mater. Res. Bull. 31, 1083–1092 (1996).

  7. 7

    Wang, C., Slough, C. G. & Coleman, R. V. Spectroscopy of dichalcogenides and trichalcogenides using scanning tunneling microscopy. J. Vac. Sci. Technol. B 9, 1048–1051 (1991).

  8. 8

    Nagata, S. et al. Superconductivity in the layered compound 2H-TaS2 . J. Phys. Chem. Solids 53, 1259–1263 (1992).

  9. 9

    Kumakura, T., Tan, H., Handa, T., Morishita, M. & Fukuyama, H. Charge density wave and superconductivity in 2H-TaSe2 . Czech. J. Phys. 46, 2611–2612 (1996).

  10. 10

    Nunezregueiro, M., Mignot, J. M., Jaime, M., Castello, D. & Monceau, P. Superconductivity under pressure in linear chalcogenides. Synth. Met. 56, 2653–2659 (1993).

  11. 11

    Mihaila, B. et al. Pinning Frequencies of the collective modes in α-uranium. Phys. Rev. Lett. 96, 76401 (2006).

  12. 12

    Jaiswal, D. et al. Superconducting parameters of a CDW compound Lu5Ir4Si10 . Physica B 312, 142–144 (2002).

  13. 13

    Singh, Y., Nirmala, R., Ramakrishnan, S. & Malik, S. K. Competition between superconductivity and charge-density-wave ordering in the Lu5Ir4(Si1-xGex)10 alloy system. Phys. Rev. B 72, 45106 (2005).

  14. 14

    Morris, R. C. Connection between charge-density waves and superconductivity in NbSe2 . Phys. Rev. Lett. 34, 1164–1166 (1975).

  15. 15

    Fang, L. et al. Fabrication and superconductivity of NaxTaS2 crystals. Phys. Rev. B 72, 14534 (2005).

  16. 16

    Bachrach, R. Z. & Skibowski, M. Angle-resolved photoemission from TiSe2 using synchrotron radiation. Phys. Rev. Lett. 37, 40–42 (1976).

  17. 17

    Woo, K. C. et al. Superlattice formation in titanium diselenide. Phys. Rev. B 14, 3242–3247 (1976).

  18. 18

    Wilson, J. A. Concerning the semimetallic characters of TiS2 and TiSe2 . Solid State Commun. 22, 551–553 (1977).

  19. 19

    Zunger, A. & Freeman, A. J. Band structure and lattice instability of TiSe2 . Phys. Rev. B 17, 1839–1842 (1978).

  20. 20

    Myron, H. W. & Freeman, A. J. Electronic structure and optical properties of layered dichalcogenides: TiS2 and TiSe2 . Phys. Rev. B 9, 481–486 (1974).

  21. 21

    Isomaki, H., Boehm, J. von & Krusius, P. Band structure of group IVA transition-metal dichalcogenides. J. Phys. C 12, 3239–3252 (1979).

  22. 22

    Stoffel, N. G., Kevan, S. D. & Smith, N. V. Experimental band structure of 1T-TiSe2 in the normal and charge-density-wave phases. Phys. Rev. B 31, 8049–8055 (1985).

  23. 23

    Kidd, T. E., Miller, T., Chou, M. Y. & Chiang, T.-C. Electron-hole coupling and the charge density wave transition in TiSe2 . Phys. Rev. Lett. 88, 226402 (2002).

  24. 24

    Oftedal, I. Roentgenographische Untersuchungen von SnS2, TiS22, TiSe2, TiTe2 . Z. Phys. Chem. 134, 301–310 (1928).

  25. 25

    Bussmann-Holder, A. & Buttner, H. Charge-density-wave formation in TiSe2 driven by an incipient antiferroelectric instability. J. Phys. Condens. Matter 14, 7973–7979 (2002).

  26. 26

    Batlogg, B et al. Superconductivity in Bi-O and Sb-O perovskites. Physica C 162–164, 1393–1396 (1989).

  27. 27

    Bardeen, J., Cooper, L. N. & Schrieffer, J. R. Theory of superconductivity. Phys. Rev. 108, 1175–1204 (1957).

  28. 28

    Hake, R. R. Upper-critical-field limits for bulk type-II superconductors. Appl. Phys. Lett. 10, 189–192 (1967).

  29. 29

    Carlin, R. L. Magnetochemistry (Springer, New York, 1986).

Download references


This research was supported primarily by the US DOE-BES solid state chemistry program, and, in part, by the US NSF MRSEC program.

Author information

Competing interests

The authors declare no competing financial interests.

Correspondence to E. Morosan or R. J. Cava.

Rights and permissions

Reprints and Permissions

About this article

Further reading

Figure 1: Lattice parameters of CuxTiSe2.
Figure 2: Magnetization and transport properties of CuxTiSe2.
Figure 3: The superconducting phase transition as a function of Cu content x.
Figure 4: Characterization of the superconductivity in Cu0.08TiSe2.
Figure 5: Summary of the composition-dependent properties in CuxTiSe2.
Figure 6: The CuxTiSe2 Tx electronic phase diagram.