the Fermi liquid theory

Fermi liquid theory describes how electrons behave in many metals at low temperatures. Although electrons are particles with their own interactions, in a metal they act collectively like a fluid of particles called quasiparticles. These quasiparticles carry charge and spin, moving through the metal with slightly altered masses and properties determined by interactions. Despite interactions, their behavior remains predictable and similar to free electrons, allowing scientists to understand and calculate properties like electrical conductivity and heat capacity. Essentially, Fermi liquid theory simplifies complex electron interactions into a framework where electrons act as if they are weakly interacting, making the metal's behavior easier to understand.