A New Electronic Pinning Mechanism for Sliding Charge Density Waves

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Abstract
It is shown that the time component of the chiral Noether current is a constant of motion in a quasi‐one‐dimensional charge density wave (CDW) system in the absence of a disordered potential. Therefore this system possesses a current‐carrying equilibrium state which is characterized as the minimum of an accordingly generalized thermodynamic potential. A random impurity potential breaks the chiral invariance so that a current‐carrying equilibrium state in the strict sense does not exist in this case. It is assumed, however, that the sliding CDW state can approximately be described as a quasi‐equlibrium in the coordinate frame co‐moving with the velocity ν. It is shown that the density of states in the co‐moving frame exhibits tails in the Peierls gap which enhance the thermodynamic potential of the quasi‐equilibrium proportional to |ν| so that the current‐driving Lagrange parameter in this potential must exceed some threshold value before the sliding CDW state is thermodynamically favoured against the resting one. This is an electronic pinning mechanism which acts independently of the conventional phase pinning.