Coulomb blockade
In mesoscopic physics, a Coulomb blockade (CB), named after Charles-Augustin de Coulomb's electrical force, is the decrease in electrical conductance at small bias voltages of a small electronic device comprising at least one low-capacitance tunnel junction.
Coulomb blockade can be observed by making a device very small, like a quantum dot.
Thus, the device will no longer follow Ohm's law and the current-voltage relation of the Coulomb blockade looks like a staircase.
[2] Even though the Coulomb blockade can be used to demonstrate the quantization of the electric charge, it remains a classical effect and its main description does not require quantum mechanics.
In the case that the electrodes are metallic or normal-conducting, i.e. neither superconducting nor semiconducting, electrons (with a charge of
The tunnel junction is, in its simplest form, a thin insulating barrier between two conducting electrodes.
According to the laws of classical electrodynamics, no current can flow through an insulating barrier.
An arrangement of two conductors with an insulating layer in between not only has a resistance, but also a finite capacitance.
The insulator is also called dielectric in this context, the tunnel junction behaves as a capacitor.
If the capacitance is very small, the voltage build up can be large enough to prevent another electron from tunnelling.
The electric current is then suppressed at low bias voltages and the resistance of the device is no longer constant.
The increase of the differential resistance around zero bias is called the Coulomb blockade.
[4][5] To make a tunnel junction in plate condenser geometry with a capacitance of 1 femtofarad, using an oxide layer of electric permittivity 10 and thickness one nanometer, one has to create electrodes with dimensions of approximately 100 by 100 nanometers.
The integration of quantum dot fabrication with standard industrial technology has been achieved for silicon.
[6] The simplest device in which the effect of Coulomb blockade can be observed is the so-called single-electron transistor.
In the blocking state no accessible energy levels are within tunneling range of an electron (in red)[clarification needed] on the source contact.
of the island, defined as To achieve the Coulomb blockade, three criteria have to be met: A typical Coulomb blockade thermometer (CBT) is made from an array of metallic islands, connected to each other through a thin insulating layer.
The parameter V½ = 5.439 NkBT/e, the full width at half minimum of the measured differential conductance dip over an array of N junctions together with the physical constants provide the absolute temperature.
Ionic Coulomb blockade[8] (ICB) is the special case of CB, appearing in the electro-diffusive transport of charged ions through sub-nanometer artificial nanopores[9] or biological ion channels.
[10] ICB is widely similar to its electronic counterpart in quantum dots,[1] but presents some specific features defined by possibly different valence z of charge carriers (permeating ions vs electrons) and by the different origin of transport engine (classical electrodiffusion vs quantum tunnelling).
[9] In biological ion channels ICB typically manifests itself in such valence selectivity phenomena as
