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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 Anderson impurity model ： ウィキペディア英語版 Anderson impurity model The Anderson impurity model is a Hamiltonian that is used to describe magnetic impurities embedded in metallic hosts. It is often applied to the description of Kondo-type of problems, such as heavy fermion systems and Kondo insulators. In its simplest form, the model contains a term describing the kinetic energy of the conduction electrons, a two-level term with an on-site Coulomb repulsion that models the impurity energy levels, and a hybridization term that couples conduction and impurity orbitals. For a single impurity, the Hamiltonian takes the form $H\; =\; \backslash sum\_\backslash epsilon\_f\; f^\_f\_\; +\; \backslash sum\_t\_\; c^\_c\_\; +\; \backslash sum\_(V\_j\; f^\_c\_\; +\; V\_j^$ * c^_f_) + Uf^_f_f^_f_ where the $f$ operator corresponds to the annihilation operator of an impurity, and $c$ corresponds to a conduction electron annihilation operator, and $\backslash sigma$ labels the spin. The onsite Coulomb repulsion is $U$, which is usually the dominant energy scale, and $t\_$ is the hopping strength from site $j$ to site $j\text{'}$. A significant feature of this model is the hybridization term $V$, which allows the $f$ electrons in heavy fermion systems to become mobile, despite the fact they are separated by a distance greater than the Hill limit. In heavy-fermion systems, we find we have a lattice of impurities. The relevant model is then the periodic Anderson model. $H\; =\; \backslash sum\_\backslash epsilon\_f\; f^\_f\_\; +\; \backslash sum\_t\_c^\_c\_\; +\; \backslash sum\_(V\_j\; f^\_c\_\; +\; V\_j^$ * c^_f_) + U\sum_f^_f_f^_f_ There are other variants of the Anderson model, for instance the SU(4) Anderson model, which is used to describe impurities which have an orbital, as well as a spin, degree of freedom. This is relevant in carbon nanotube quantum dot systems. The SU(4) Anderson model Hamiltonian is $H\; =\; \backslash sum\_\backslash epsilon\_f\; f^\_f\_\; +\; \backslash sum\_t\_\; c^\_c\_\; +\; \backslash sum\_(V\_j\; f^\_c\_\; +\; V\_j^$ * c^_f_) + \sum_ \fracn_n_ where i and i' label the orbital degree of freedom (which can take one of two values), and n represents a number operator. == See also == *Kondo effect *Kondo model 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「Anderson impurity model」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.