A charge density wave (CDW) is an ordered quantum fluid of electrons in a linear chain compound or layered crystal.
The electrons in such a CDW, like those in a superconductor, can flow through a linear chain compound en masse, in a highly correlated fashion.
Unlike a superconductor, however, the electric CDW current often flows in a jerky fashion, much like water dripping from a faucet, due to its electrostatic properties.
In 1954, Herbert Fröhlich proposed a microscopic theory,[5] in which energy gaps at ±kF would form below a transition temperature as a result of the interaction between the electrons and phonons of wavevector Q=2kF.
Conduction at high temperatures is metallic in a quasi-1-D conductor, whose Fermi surface consists of fairly flat sheets perpendicular to the chain direction at ±kF.
Fröhlich thus proposed that the CDW could move and, moreover, that the Peierls gaps would be displaced in momentum space along with the entire Fermi sea, leading to an electric current proportional to dφ/dt.
[10][11][12] Early studies of quasi-1-D conductors were motivated by a proposal, in 1964, that certain types of polymer chain compounds could exhibit superconductivity with a high critical temperature Tc.
Since light electrons, instead of heavy ions, would lead to the formation of Cooper pairs, their characteristic frequency and, hence, energy scale and Tc would be enhanced.
[25] However, a 1985 paper by Krive and Rozhavsky[26] pointed out that nucleated solitons and antisolitons of charge ±q generate an internal electric field E* proportional to q/ε.
Although this Coulomb blockade threshold can be much smaller than the classical depinning field, it shows the same scaling with impurity concentration since the CDW's polarizability and dielectric response ε vary inversely with pinning strength.
The narrow-band noise and related phenomena result from the periodic buildup of electrostatic charging energy and thus do not depend on the detailed shape of the washboard pinning potential.
[32] The first evidence for phenomena related to the Aharonov–Bohm effect in CDWs was reported in a 1997 paper,[33] which described experiments showing oscillations of period h/2e in CDW (not normal electron) conductance versus magnetic flux through columnar defects in NbSe3.