Cuprate superconductors, discovered in 1986, still confront researchers of condensed matter physics with unresolved challenges. On top of this, superconductivity research is now booming again—thanks to recent studies that demonstrate how phenomena like charge order and fluctuations can coexist and interact with high-temperature superconductivity.

To help researchers approach the daunting amount of literature on this subject, the Special Topics issue of the Journal of the Physical Society of Japan includes 12 papers on recent experimental and theoretical research on remarkable new phenomena in high-temperature superconductors.

First, Uchida provides an overview of the field and future prospects, while Tranquada and colleagues pursue the relationship between charge order and superconductivity using scattering and transport techniques in cuprate families.

Fujita and colleagues provide an atomic-scale visualization of Cooper-pair density waves using scanning tunneling microscopy techniques. Meanwhile, Lee summarizes recent findings on the charge density wave in superconducting cuprates using X-ray scattering.

Also employing X-ray scattering techniques, Arpaia and Ghiringhelli explore high temperature and high energy charge fluctuations, whereas Le Tacon and colleagues investigate charge order and phonon anomalies under uniaxial stress.

Abbamonte and colleagues search for a new ordered state using X-ray diffraction, and Kawasaki and colleagues employ nuclear magnetic resonance to probe charge order and fluctuations.

On the theoretical side, Imada explores the relationships between charge order and superconductivity and how to measure them using spectroscopic methods.

Devereaux and colleagues analyze charge-spin fluctuations using large-scale numerical calculation of the Hubbard model, while Yamase delves into the theory of bond charge order, collective charge fluctuations, and nematic order. Finally, Kontani and colleagues explore the theory of various liquid crystal orders in cuprate superconductors and related materials.

The sheer amount of knowledge that has been accumulated on high-temperature superconductivity makes it hard for new researchers to approach the subject, but this issue will hopefully be a useful source of information so that anyone can approach and grasp the hottest spots of the field.