Anderson localization

Japanese: アンダーソン局在 - アンダーソンきょくざい（英語表記）Anderson localization

A phenomenon in which electrons become spatially localized due to crystal disorder, making the entire crystal immobile. The possibility was pointed out by American physicist Philip W. Anderson in 1958. The electrical conduction of crystals such as metals is strongly affected by disorder such as the concentration of impurities and lattice defects, and when the disorder is small, the electrical conductivity is roughly inversely proportional to the magnitude of the disorder. Anderson believed that the conductivity does not gradually approach zero as the disorder of the crystal increases, but that when the disorder reaches a certain level, the conductivity becomes zero, that is, a transition occurs from metal to insulator. The cause of this transition is Anderson localization. At the end of the 1970s, there was a remarkable development in theoretical research, making it possible to quantitatively compare with experiments. As a result, the phenomenon of negative magnetoresistance, which had been observed in quasi-two-dimensional systems on semiconductor surfaces and semiconductors with high impurity concentrations but had remained unexplained for many years, was elucidated based on Anderson localization, and many new insights were obtained about the behavior of electrons in solids.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

結晶の乱れにより，電子が空間的に局在して結晶全体を動けなくなる現象。1958年にアメリカ合衆国の物理学者フィリップ・W.アンダーソンが可能性を指摘した。金属など結晶の電気伝導は，不純物や格子欠陥の濃度などの乱れに強く影響を受け，乱れが小さい場合に電気伝導率は乱れの大きさにほぼ反比例する。アンダーソンは，結晶の乱れが大きくなるにつれて伝導率がしだいにゼロに近づくのではなく，乱れがある大きさになると伝導率がゼロになる，つまり金属から絶縁体へ転移すると考えた。この転移の原因となるのがアンダーソン局在である。1970年代末，理論研究のめざましい発展があり，実験との定量的な比較が可能となった。その結果，半導体表面の準2次元系や高濃度不純物半導体で観測されながら，長年解明されずにいた負の磁気抵抗効果の現象が，アンダーソン局在に基づいて解明され，固体内の電子のふるまいについて多くの新たな知見が得られた。

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