Electric field control of high-Tc cuprates in the entire doping range
1. Superconductor-insulator transition in La_{2-x}Sr_{x}CuO_{4} at the pair quantum resistance
Authors: A. T. Bollinger, G. Dubuis, J. Yoon, D. Pavuna, J. Misewich, and I. Bozovic
Nature 472, 458-460 (2011)
2. Electrostatic control of the evolution from a superconducting phase to an insulating
phase in ultrathin YBa_{2}Cu_{3}O_{7-x} films
Authors: X. Leng, J. Garcia-Barriocanal, S. Bose, Y. Lee, and A. M. Goldman
Phys. Rev. Lett. 107, 027001 (2011)
3. Indications of an electronic phase transition in 2D YBa_{2}Cu_{3}O_{7-x} induced by electrostatic doping
Authors: X. Leng, J. Garcia-Barriocanal, B. Yang, Y. Lee, and A. M. Goldman
arXiv:1108.0083v1
Recommended with a Commentary by Atsushi Fujimori, University of Tokyo |View Commentary (pdf)|
DOI: 10.36471/JCCM_October_2011_02
https://doi.org/10.36471/JCCM_October_2011_02
I have looked with interest to the commentary by Fujimori about the field effect control of the doping in cuprates.
I have no doubt that these experiments represent a very interesting progress which we have been waiting for many years now. This opens novel possibilities for superconductivity driven components and might certainly result in scientific applications and hopefully in technical ones as well.
I am however somewhat sceptical and would even seriously disagree about the comment done by Fujimori: “Unlike chemical doping, disorder remains unchanged by the electric field doping.”
This is in my opinion a wishful thinking for a one layer thickness material. Idealizing the materials is always an easy trend in the scientific community. Any material scientist should be aware that defects and complications always arise. For instance the charges accumulating in the interface layer which drive the “uniform” electric field in the layer will certainly be trapped at some defects of the interface, and new locations will be favoured when the field is modified.
I take as an example, for instance, the study of the metal insulator transition (MIT) in the underdoped samples. The work we have done a few years ago (1) on the incidence of disorder on the MIT in single crystals demonstrated that the MIT is driven by disorder as it depends markedly on the considered cuprate family, so that the observation of a MIT in these one layer thick samples is really by itself a confirmation that disorder is present. It probably has even more incidence than in single crystals of the cleanest cuprate families.
One can always dream, but I am probably on the pessimistic side, and we know that similar dreams have not been achieved so far in single crystals after more than 20 years of hard work, even if real improvements have been achieved.
(1) F. Rullier-Albenque, H. Alloul, F. Balakirev and C. Proust, “Disorder, Metal-Insulator crossover and Phase Diagram in High-Tc cuprates”, Europhysics Lett. 81, 37008 (2008).