In physics, low-energy excitation refers to the process by which a physical system transitions from its ground state to a state of higher energy, but with energy levels that are relatively close to the ground state. These excitations are characterized by small energy differences compared to the overall energy scale of the system.
The concept of low-energy excitation is particularly relevant in condensed matter physics, where it is used to describe the behavior of atoms, molecules, and particles in solid materials. In such systems, the ground state represents the lowest energy configuration that the system can adopt. Exciting the system involves adding energy to it, causing it to enter a higher energy state.
Low-energy excitations are important because they can reveal valuable information about the properties and behavior of a system. For example, in the context of electronic systems, low-energy excitations can correspond to the movement of electrons within a material or the formation of electron-hole pairs. Studying these excitations can help researchers understand phenomena such as electrical conductivity, magnetism, and optical properties.
The term "low-energy" is relative and depends on the specific system under consideration. For instance, in particle physics, low-energy excitations may refer to processes occurring at energies significantly below the characteristic energy scale of high-energy particle interactions, such as those studied at particle accelerators.
In summary, low-energy excitation refers to the process of raising a system's energy levels to states relatively close to its ground state. The study of such excitations provides insight into the behavior and properties of physical systems.