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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Bose-Einstein condensation of excitons ： ウィキペディア英語版 Bose-Einstein condensation of quasiparticles Bose-Einstein condensation can occur in quasiparticles, particles that are effective descriptions of collective excitations in materials. Some have integer spins and can be expected to obey Bose-Einstein statistics like traditional particles. Conditions for condensation of various quasiparticles have been predicted and observed. The topic continues to be an active field of study. == Properties == BECs form when low temperatures cause nearly all particles to occupy the lowest quantum state. Condensation of quasiparticles occurs in ultracold gases and materials. The lower masses of material quasiparticles relative to atoms lead to higher BEC temperatures. An ideal Bose gas has a phase transitions when inter-particle spacing approaches the thermal De-Broglie wavelength: $k\_B\; T\; =~\; \backslash hbar^2\; n^/M$. The critical concentration is then $N\; \backslash propto\; (T/2\; \backslash pi)^3\; u^\; P\; /\; v\; \backslash hbar^3$, leading to a critical temperature: . The particles obey the Bose-Einstein distribution and all occupy the ground state: The Bose gas can be considered in a harmonic trap, $V(r)\; =\; M\; \backslash omega^2\; /2$, with the ground state occupancy fraction as a function of temperature: $f(0)\; =\; N\_0(t)/N\; =\; 1\; -\; (T/T\_c)^3$ This can be achieved by cooling and magnetic or optical control of the system. Spectroscopy can detect shifts in peaks indicating thermodynamic phases with condensation. Quasiparticle BEC can be superfluids. Signs of such states include spatial and temporal coherence and polarization changes. Observation for excitons in solids was seen in 2005 and for magnons in materials and polaritons in microcavities in 2006. Graphene is another important solid state system for studies of condensed matter including quasi particles; It's a 2D electron gas, similar to other thin films. 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「Bose-Einstein condensation of quasiparticles」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.