Letters to Nature

Nature 394, 453-456 (30 July 1998) | doi:10.1038/28810; Received 13 March 1998; Accepted 27 May 1998

Doubling the critical temperature of La1.9Sr0.1CuO4 using epitaxial strain

J.-P. Locquet1, J. Perret1,2, J. Fompeyrine1,3, E. Mächler1, J. W. Seo1,2 & G. Van Tendeloo4

  1. IBM Research Division, Zurich Research Laboratory, CH-8803 Rüschlikon, Switzerland
  2. Institut de Physique, Université de Neuchâtel, CH-2000 Neuchâtel, Switzerland
  3. Institute of Inorganic Chemistry, University of Bern, CH-3012 Bern>, Switzerland
  4. EMAT, RUCA, University of Antwerp, B-2020 Antwerpen, Belgium

Correspondence to: J.-P. Locquet1 Correspondence and requests for materials should be addressed to J.-P.L. (e-mail: Email: loc@zurich.ibm.com).

The discovery1 of high-temperature superconductivity in copper oxides raised the possibility that superconductivity could be achieved at room temperature. But since 1993, when a critical temperature (T c) of 133 K was observed in the HgBa2Ca2Cu3O8+delta (ref. 2), no further progress has been made in raising the critical temperature through material design. It has been shown, however, that the application of hydrostatic pressure can raise T c — up to approx164 K in the case of HgBa2Ca2Cu3O8+delta (ref. 3). Here we show, by analysing the uniaxial strain and pressure derivatives of T c, that compressive epitaxial strain in thin films of copper oxide superconductors could in principle generate much larger increases in the critical temperature than obtained by comparable hydrostatic pressures. We demonstrate the experimental feasibility of this approach for the compound La1.9Sr0.1CuO4, where we obtain a critical temperature of 49 K in strained single-crystal thin films — roughly double the bulk value of 25 K. Furthermore, the resistive behaviour at low temperatures (but above T c) of the strained samples changes markedly, going from insulating to metallic.