Collective excitation refers to coherent states of many-body systems where particles or quasiparticles organize in modes, leading to phenomena beyond individual particle behavior. These excitations play a critical role in describing phenomena in condensed matter physics, including superconductivity and superfluidity.

Collective Excitation

Coherent states are quantum states of the harmonic oscillator that most closely resemble classical harmonic motion, representing minimum uncertainty wave packets. They preserve their shape and width over time, allowing for unique applications in quantum optics and quantum information theory.

Coherent States

Many-body systems refer to systems composed of a large number of interacting particles, where the collective behavior cannot be easily deduced from the properties of individual components. Understanding these systems is crucial in fields like condensed matter physics, statistical mechanics, and quantum mechanics, as they exhibit complex phenomena such as phase transitions and emergent properties.

Many-body Systems

Particles

Quasiparticles are emergent phenomena that occur in many-body systems, where the collective behavior of particles can be described as if they were individual particles with modified properties. They provide a useful framework for understanding complex interactions in condensed matter physics, such as in superconductors and quantum Hall systems.

Quasiparticles

Modes

Individual particle behavior

Phenomena

Condensed matter physics is the branch of physics that deals with the physical properties of condensed phases of matter, such as solids and liquids. It seeks to understand the behavior of these phases through principles of quantum mechanics, electromagnetism, and statistical mechanics, leading to applications in technology and materials science.

Condensed Matter Physics

Superconductivity is a quantum mechanical phenomenon where a material exhibits zero electrical resistance and expulsion of magnetic fields below a critical temperature. This allows for highly efficient energy transmission and powerful magnetic applications, but practical use is limited by the need for extremely low temperatures or high pressures.

Superconductivity

Superfluidity is a phase of matter characterized by the complete absence of viscosity, allowing it to flow without dissipating energy. It typically occurs at very low temperatures in certain liquids like helium-4, where quantum mechanical effects become significant on a macroscopic scale.

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