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Avoided Quantum Criticality in YBa_2Cu_3O_y and La_{2-x}Sr_xCuO_4

J. E. Sonier·F. D. Callaghan·Y. Ando·R. F. Kiefl·J. H. Brewer·C. V. Kaiser·V. Pacradouni·S. -A. Sabok-Sayr·X. F. Sun·S. Komiya·W. N. Hardy·D. A. Bonn·R. Liang
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Abstract

Spin-glass magnetism confined to individual weakly interacting vortices is detected in two different families of high-transition-temperature (T_c) superconductors, but only in samples on the low-doping side of the low-temperature normal state metal-to-insulator crossover (MIC). Our findings unravel the mystery of the MIC, but more importantly identify the true location of the field-induced quantum phase transition (QPT) in the superconducting state. The non-uniform appearance of magnetism in the vortex state favours a surprisingly exotic phase diagram, in which spatially inhomogeneous competing order is stabilized at the QPT, and an `avoided' quantum critical point (QCP) is realized at zero magnetic field.

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J. E. Sonier, F. D. Callaghan, Y. Ando, R. F. Kiefl, J. H. Brewer, C. V. Kaiser, V. Pacradouni, S. -A. Sabok-Sayr, X. F. Sun, S. Komiya, W. N. Hardy, D. A. Bonn, R. Liang. 2006-10-02. Avoided Quantum Criticality in YBa_2Cu_3O_y and La_{2-x}Sr_xCuO_4. https://arxiv.org/abs/cond-mat/0610051

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