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Zeeman effect in superconducting two-leg ladders: irrational magnetization plateaus and exceeding the Pauli limit

G. Roux·S. R. White·S. Capponi·D. Poilblanc
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Abstract

The effect of a parallel magnetic field on superconducting two-leg ladders is investigated numerically. The magnetization curve displays an irrational plateau at a magnetization equal to the hole density. Remarkably, its stability is fundamentally connected to the existence of a well-known magnetic resonant mode. Once the zero-field spin gap is suppressed by the field, pairs acquire a finite momentum characteristic of a Fulde-Ferrell-Larkin-Ovchinnikov phase. In addition, S^z=0 triplet superconducting correlations coexist with singlet ones above the irrational plateau. This provides a simple mechanism in which the Pauli limit is exceeded as suggested by recent experiments.

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G. Roux, S. R. White, S. Capponi, D. Poilblanc. 2006-08-23. Zeeman effect in superconducting two-leg ladders: irrational magnetization plateaus and exceeding the Pauli limit. https://doi.org/10.1103/physrevlett.97.087207

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