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In physics, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, like solids and some liquids. Often designated a quasiparticle,〔F. Schwabl, ''Advanced Quantum Mechanics'', 4th Ed., Springer (2008), p. 253〕 it represents an excited state in the quantum mechanical quantization of the modes of vibrations of elastic structures of interacting particles. Phonons play a major role in many of the physical properties of condensed matter, like thermal conductivity and electrical conductivity. The study of phonons is an important part of condensed matter physics. The concept of phonons was introduced in 1932 by Soviet physicist Igor Tamm. The name ''phonon'' comes from the Greek word ''φωνή'' (phonē), which translates to ''sound'' or ''voice'' because long-wavelength phonons give rise to sound. Shorter-wavelength higher-frequency phonons give rise to heat. ==Definition== A phonon is a quantum mechanical description of an elementary vibrational motion in which a lattice of atoms or molecules uniformly oscillates at a single frequency. In classical mechanics this is designated a normal mode. Normal modes are important because any arbitrary lattice vibration can be considered to be a superposition of these ''elementary'' vibrations (cf. Fourier analysis). While normal modes are wave-like phenomena in classical mechanics, phonons have particle-like properties too, in a way related to the wave–particle duality of quantum mechanics. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phonon」の詳細全文を読む スポンサード リンク
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