Введение
Квантованная единица электрической проводимости
The conductance quantum, denoted by the symbol G0, is the quantized unit of electrical conductance. It is defined by the elementary charge e and Planck constant h as:
=
It appears when measuring the conductance of a quantum point contact, and, more generally, is a key component of the 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/RK). Note that the conductance quantum does not mean that the conductance of any system must be an integer multiple of G0. 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 G0. 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.
Квант проводимости, обозначаемый символом G0, является квантованной единицей электрической проводимости. Он определяется элементарным зарядом e и постоянной Планка h как:
The conductance quantum, denoted by the symbol G0, is the quantized unit of electrical conductance. It is defined by the elementary charge e and Planck constant h as:
=
It appears when measuring the conductance of a quantum point contact, and, more generally, is a key component of the 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/RK). Note that the conductance quantum does not mean that the conductance of any system must be an integer multiple of G0. 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 G0. 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.
=
The conductance quantum, denoted by the symbol G0, is the quantized unit of electrical conductance. It is defined by the elementary charge e and Planck constant h as:
=
It appears when measuring the conductance of a quantum point contact, and, more generally, is a key component of the 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/RK). Note that the conductance quantum does not mean that the conductance of any system must be an integer multiple of G0. 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 G0. 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.
Он проявляется при измерении проводимости квантового точечного контакта и, в более общем смысле, является ключевым компонентом формулы Ландауэра, связывающей электрическую проводимость квантового проводника с его квантовыми свойствами. Он равен двум, деленным на постоянную фон Клицинга (2/RK). Важно отметить, что квант проводимости не подразумевает, что проводимость любой системы должна быть целым кратным G0. Вместо этого он описывает проводимость двух квантовых каналов (один канал для электронов со спином вверх и один для спином вниз), если вероятность прохождения электрона через канал равна единице, то есть если транспорт через канал является баллистическим. Если вероятность прохождения меньше единицы, то проводимость канала будет меньше G0. Общая проводимость системы равна сумме проводимостей всех параллельных квантовых каналов, из которых состоит система.
The conductance quantum, denoted by the symbol G0, is the quantized unit of electrical conductance. It is defined by the elementary charge e and Planck constant h as:
=
It appears when measuring the conductance of a quantum point contact, and, more generally, is a key component of the 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/RK). Note that the conductance quantum does not mean that the conductance of any system must be an integer multiple of G0. 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 G0. 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.
Возникновение
Квантованная проводимость наблюдается в проводниках, являющихся баллистическими проводниками, когда упругий средний свободный пробег значительно превышает длину проводника: B. J. van Wees и др. впервые наблюдали этот эффект в точечном контакте в 1988 году. Углеродные нанотрубки демонстрируют квантованную проводимость, не зависящую от диаметра. Квантовый эффект Холла может быть использован для точного измерения значения квантовой проводимости. Он также проявляется в электрохимических реакциях и, в сочетании с квантовой ёмкостью, определяет скорость переноса электронов между квантово-химическими состояниями, как это описано в квантовой теории скорости реакций.