2014/12/02 by Xiaoyan Shi, Ping V. Lin, T. Sasagawa +2 · 1 citation
Physics and Astronomy · #cond-mat.supr-con
paper · pdf · doi:10.1038/nphys2961
published as Nature Phys. 10, 437-443 (2014) · 23 pages, 5 figures, and Supplementary Information (11 pages, 7 figures); Article
arxiv created 2014/12/02 · arxiv updated 2014/12/04
In the underdoped pseudogap regime of cuprate superconductors, the normal state is commonly probed by applying a magnetic field (H). However, the nature of the H-induced resistive state has been the subject of a long-term debate, and clear evidence for a zero-temperature (T=0) H-tuned superconductor-insulator transition (SIT) has proved elusive. Here we report magnetoresistance measurements in underdoped La2-xSrxCuO4, providing striking evidence for quantum critical behavior of the resistivity -- the signature of a H-driven SIT. The transition is not direct: it is accompanied by the emergence of an intermediate state, which is a superconductor only at T=0. Our finding of a two-stage H-driven SIT goes beyond the conventional scenario in which a single quantum critical point separates the superconductor and the insulator in the presence of a perpendicular H. Similar two-stage H-driven SIT, in which both disorder and quantum phase fluctuations play an important role, may also be expected in other copper-oxide high-temperature superconductors.