Cuprate superconductors have been a focus of fascination for four decades. They exhibit states such as antiferromagnetism and charge order that conflict with the conventional requirements for electron pairing, so that such states are commonly referred to as competing orders. I will make the case that a proper understanding requires an unconventional perspective [1,2]. As supported by experimental evidence, the charge stripes that develop between antiphase spin stripes should be viewed as hole-doped two-leg spin ladders, in which pairing is driven by the large singlet-triplet excitation gap associated with the superexchange between nearest-neighbor Cu moments. The spin stripes that enable this pairing mechanism also represent a hurdle for establishing the phase locking between pairing correlations in neighboring charge stripes that is necessary to achieve superconducting order. I will discuss how this picture explains the observations of both unusual pair-density-wave order and spatially-uniform d-wave superconductivity.
- M. Tranquada, Adv. Phys. 69, 437 (2020).
- M. Tranquada, Symmetry 13, 2365 (2021).