Cuprate Superconductors as Viewed through a Striped Lens

Abstract

The nature of electron pairing in cuprate superconductors remains controversial.  I will argue that experiments on compounds with spin and charge stripe orders provide a Rosetta stone for interpreting the cuprates.  While stripe order competes with three-dimensional superconductivity, charge stripes in La_2-xBa_xCuO₄ are actually good for pairing [1,2].  Taking a lesson from nickelates [3], the antiphase character of spin stripes decouples them from the charge stripes, yielding independent spin degrees of freedom.  For cuprates, this means we can understand pairing in terms of correlations on a single charge stripe, viewing it as a hole-doped, two-leg spin ladder, where the pairing scale is set by the singlet-triplet excitation energy of the local moments.  This picture provides a new understanding of the observed magnetic excitation spectrum [4]. To obtain spatially uniform d-wave superconductivity, it is necessary to gap the antiphase spin correlations [5].  The identified energy scales apply to all hole-doped cuprates that have been characterized, as I will show.

1.     Y. Li et al., Sci. Adv. 5, eaav7686 (2019).

2.     E. Fradkin, S. A. Kivelson, and J. M. Tranquada, Rev. Mod. Phys. 87, 457 (2015).

3.     A. M. Merritt et al., Phys. Rev. B 100, 195122 (2019).

4.     J. M. Tranquada et al., Nature 429, 534 (2004).

5.     Y. Li et al., Phys. Rev. B 98, 224508 (2018).