Strongly Correlated High-Entropy Materials: Electronic and Phononic States under Disorder

High-entropy compounds (HECs), stabilized by configurational entropy associated with random elemental occupation, have rapidly expanded the landscape of solid-state chemistry. While research has primarily focused on high-entropy alloys (HEAs) and oxides (HEOs), a broader spectrum of HECs has recently emerged, spanning metallic, insulating, and intermediate regimes. This perspective classifies HECs into three categories based on their electrical conductivity─HEAs, HEOs, and compounds with nonoxide anions─and highlights how anion chemistry and structural dimensionality govern their electronic states. Particular attention is paid to superconductivity, which consistently exhibits s-wave pairing but displays unusual robustness under extreme pressure and disorder, revealing enhanced upper critical fields and strong-coupling behavior. We further discuss pioneering studies that directly probe electronic and phononic states, underscoring the unique role of chemical disorder in shaping correlation effects and lattice dynamics. By situating HECs at the intersection of strong electron correlation, disorder, and entropy stabilization, this article outlines current challenges and points to future opportunities for designing functional quantum materials through entropy engineering.