Angular Fluctuations of a Multicomponent Order Describe the Pseudogap of \(YBa_2Cu_3O_{6+x}\)

Abstract

The hole-doped cuprate high-temperature superconductors enter the pseudogap regime as their superconducting critical temperature, \(T_c\), falls with decreasing hole density. Recent x-ray scattering experiments in \(YBa_2Cu_3O_{6+x}\) observe incommensurate charge-density wave fluctuations whose strength rises gradually over a wide temperature range above \(T_c\), but then decreases as the temperature is lowered below \(T_c\). We propose a theory in which the superconducting and charge-density wave orders exhibit angular fluctuations in a six-dimensional space. The theory provides a natural quantitative fit to the x-ray data and can be a basis for understanding other characteristics of the pseudogap.