Superconductivity in just four pairs of (BETS)2GaCl4 molecules

Abstract

How small can a sample of superconducting material be and still display superconductivity? This question is relevant to our fundamental understanding of superconductivity, and also to applications in nanoscale electronics, because Joule heating of interconnecting wires is a major problem in nanoscale devices. It has been shown that ultrathin layers of metal can display superconductivity1,2,3, but any limits on the size of superconducting systems remain a mystery. (BETS)2GaCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene, is an organic superconductor, and in bulk it has a superconducting transition temperature Tc of 8 K (ref. 4) and a two-dimensional layered structure5,6,7 that is reminiscent of the high-Tc cuprate superconductors8,9. Here, we use scanning tunnelling spectroscopy to show that a single layer of (BETS)2GaCl4 molecules on an Ag(111) surface displays a superconducting gap that increases exponentially with the length of the molecular chain. Moreover, we show that a superconducting gap can still be detected for just four pairs of (BETS)2GaCl4 molecules. Real-space spectroscopic images directly visualize the chains of BETS molecules as the origin of the superconductivity.

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Figure 1: Structural and electronic properties of the nanoscale molecular superconductor.
Figure 2: Molecular superconductivity.
Figure 3: Size-dependent molecular superconductivity.
Figure 4: Spectroscopic maps.

References

  1. 1

    Qin, S., Kim, J., Niu, Q. & Shih. C.-K. Superconductivity at the two-dimensional limit. Science 324, 1314–1317 (2009).

    CAS  Article  Google Scholar 

  2. 2

    Özer, M. M., Jia, Y., Zhang, Z., Thompson, J. R. & Weitering, H. H. Tuning the quantum stability and superconductivity of ultrathin metal alloys. Science 316, 1594–1597 (2007).

    Article  Google Scholar 

  3. 3

    Zhang, T. et al. Superconductivity in one-atomic-layer metal films grown on Si(111). Nature Phys. 6, 104–108 (2010).

    CAS  Article  Google Scholar 

  4. 4

    Kushch, N. D. et al. New BETS salts based on magnetic (CuCl3, FeCl4) and non-magnetic (GaCl4) anions. Adv. Mater. Opt. Electron. 7, 57–60 (1997).

    CAS  Article  Google Scholar 

  5. 5

    Uji, S. et al. Magnetic-field-induced superconductivity in a two-dimensional organic conductor. Nature 410, 908–910 (2001).

    CAS  Article  Google Scholar 

  6. 6

    Kobayashi, H., Tomita, H., Udagawa, T., Naito, T. & Kobayashi, A. New organic superconductor λ-(BETS)2GaCl4 and metal–insulator transition of BETS conductor with magnetic anions (BETS = bis(ethlenedithio)tetraselenafulvalene). Synthet. Metals 70, 867–870 (1995).

    CAS  Article  Google Scholar 

  7. 7

    Kobayashi, H. et al. A new organic superconductor, λ-(BEDT-TSF)2GaCl4 . Chem. Lett. 9, 1559–1562 (1993).

    Article  Google Scholar 

  8. 8

    Bednorz, J. G. & Müller, K. A. Possible high Tc superconductivity in the Ba–La–Cu–O system. Z. Phys. B 64, 189–193 (1986).

    CAS  Article  Google Scholar 

  9. 9

    Beno, M. A. et al. Structure of the single-phase high-temperature superconductor YBa2Cu3O-delta. Appl. Phys. Lett. 51, 57–59 (1987).

    CAS  Article  Google Scholar 

  10. 10

    Jérome, D., Mazaud, A., Ribault, M. & Bechgaard, K. Superconductivity in a synthetic organic conductor (TMTSF)2PF6 . J. Physique Lett. 41, L95–L98 (1980).

    Article  Google Scholar 

  11. 11

    Nam, M.-S., Ardavan, A. S., Blundell, J. & Schlueter, J. A. Fluctuating superconductivity in organic molecular metals close to the Mott transition. Nature 449, 584–587 (2007).

    CAS  Article  Google Scholar 

  12. 12

    Kanoda, K. Electron correlation, metal–insulator transition and superconductivity in quasi-2D organic systems, (ET)(2)X. Physica C 282, 299–302(1997).

    Article  Google Scholar 

  13. 13

    Kanoda, K. Recent progress in NMR studies on organic conductors. Hyperfine Interactions 104, 235–249 (1997).

    CAS  Article  Google Scholar 

  14. 14

    Mielke, C. et al. Superconducting properties and Fermi-surface topology of the quasi-two-dimensional organic superconductor λ-(BETS)2GaCl4 (BETS = bis(ethylene-dithio)tetraselenafulvalene). J. Phys. Condens. Matter 13, 8325–8345 (2001).

    CAS  Article  Google Scholar 

  15. 15

    Brooks, J. S. Superconductivity in Organic Conductors 463–493 (Springer, 2007).

    Google Scholar 

  16. 16

    Powell, B. J. & McKenzie, R. H. Strong electronic correlations in superconducting organic charge transfer salts. J. Phys. Condens. Matter 18, R827–R866 (2006).

    CAS  Article  Google Scholar 

  17. 17

    Takabayashi, Y. et al. The disorder-free non-BCS superconductor Cs3C60 emerges from an antiferromagnetic insulator parent state. Science 323, 1585–1590 (2009).

    CAS  Article  Google Scholar 

  18. 18

    Kobayashi, H., Cui, H. & Kobayashi, A. Organic metals and superconductors based on BETS (BETS = bis(ethylenedithio)tetraselenafulvalene). Chem. Rev. 104, 5265–5288 (2004).

    CAS  Article  Google Scholar 

  19. 19

    Schrieffer, J. R. Theory of Superconductivity (W. A. Benjamin, 1964).

    Google Scholar 

  20. 20

    Kohsaka, Y. et al. How Cooper pairs vanish approaching the Mott insulator in Bi2Sr2CaCu2O8+δ . Nature 454, 1072–1078 (2008).

    CAS  Article  Google Scholar 

  21. 21

    Pasupathy, A. N. et al. Pairing interaction in the high-Tc superconductor Bi2Sr2CaCu22O8+δ . Science 320, 196–201 (2008).

    CAS  Article  Google Scholar 

  22. 22

    Arai, T. et al. Tunneling spectroscopy on the organic superconductor k-BEDT-TTF2Cu(NCS)2 using STM. Phys. Rev. B 63, 104518 (2001).

    Article  Google Scholar 

  23. 23

    Ichimura, K., Takami, M. & Nomura, K. Direct observation of d-wave superconducting gap in κ-(BEDT-TTF)2Cu[N(CN)2]Br with scanning tunneling microscope. J. Phys. Soc. Jpn 77, 114707 (2008).

    Article  Google Scholar 

  24. 24

    Hla, S.-W. STM single atom/molecule manipulation and its application to nanoscience and technology. J. Vac. Sci. Technol. B 23, 1351–1360 (2005).

    CAS  Article  Google Scholar 

  25. 25

    Perdew, J. P., Burke, S. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    CAS  Article  Google Scholar 

  26. 26

    Ozyuzer, L. et al. Tunneling spectroscopy of Tl2Ba2CuO6 . Physica C 320, 9–19 (1999).

    CAS  Article  Google Scholar 

  27. 27

    Tanatar, M. A., Ishiguro, T., Tanaka, H., Kobayashi, A. & Kobayashi, H. Anisotropy of the upper critical field of the organic superconductor λ-(BETS)2GaCl4 . J. Supercond. 12, 511–514 (1999).

    CAS  Article  Google Scholar 

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Acknowledgements

The authors would like to thank the US Department of Energy (Basic Energy Sciences; DE-FG02-02ER46012), the Ohio University Bionanotechnology Initiative and the Ohio Supercomputing Center (PHS0275).

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S.W.H. and A.H. conceived and designed the experiments. K.C., A.H. and S.K. performed the STM experiments. K.C., S.W.H. and A.H. analysed the data. K.F.B. performed the DFT calculation. H.T. performed synthesis and X-ray diffraction characterization of the molecular crystals. S.W.H. and A.H. co-wrote the paper. All the authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to A. Hassanien or S.-W. Hla.

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The authors declare no competing financial interests.

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Clark, K., Hassanien, A., Khan, S. et al. Superconductivity in just four pairs of (BETS)2GaCl4 molecules. Nature Nanotech 5, 261–265 (2010). https://doi.org/10.1038/nnano.2010.41

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