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The conductance quantum, denoted by the symbol is the quantized unit of electrical conductance. It is defined as: = . It appears when measuring the conductance of a quantum point contact, and, more generally, is a key component of Landauer formula which relates the electrical conductance of a quantum conductor to its quantum properties. It is twice the reciprocal of the von Klitzing constant (2/''R''K). Note that the conductance quantum does not mean that the conductance of any system must be an integer multiple of ''G''0. Instead, it describes the conductance of two quantum channels (one channel for spin-up and one channel for spin-down) if the probability for transmitting an electron that enters the channel is unity, i.e. if transport through the channel is ballistic. If the transmission probability is less than unity, then the conductance of the channel is less than ''G''0. The total conductance of a system is equal to the sum of the conductances of all the parallel quantum channels that make up the system.〔S. Datta, ''Electronic Transport in Mesoscopic Systems'', Cambridge University Press, 1995, ISBN 0-521-59943-1〕 == Derivation == In a 1D wire adiabaticly connecting two reservoirs of potential u1 and u2, the density of states is: and the voltage is . The 1D current going across is the current density: . 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「conductance quantum」の詳細全文を読む スポンサード リンク
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