Theory of subgap interchain tunneling in quasi 1D conductors

Abstract

We suggest a theory of internal coherent tunneling in the pseudogap region when the applied voltage U is below the free electron gap 2⌬ 0 . We address quasi-one-dimensional ͑quasi 1D͒ systems, where the gap is originated by spontaneous lattice distortions of the incommensurate charge density wave type. The results can be adjusted also to quasi 1D superconductors. The instanton approach allows one to calculate the interchain tunneling current both in single electron ͑amplitude solitons, i.e., spinons͒ and bielectron ͑phase slips͒ channels. Transition rates are governed by a dissipative dynamics originated by the emission of gapless phase excitations in the course of the instanton process. We find that the single-electron tunneling is allowed down to the true pair-breaking threshold at U c1 =2W as Ͻ 2⌬ 0 , where W as =2/ ⌬ 0 is the amplitude soliton energy. Most importantly, the bielectronic tunneling stretches down to U c2 =0 ͑in the 1D regime͒. In both cases, the threshold behavior is given by power laws J ϳ͑U − U c ͒ ␤ , where the exponent ␤ ϳ v F / u is as large as the ratio of the Fermi velocity v F and the phase u. In the two-dimensional or three-dimensional ordered phases, at temperature T Ͻ T c , the one-electron tunneling current does not vanish at the threshold anymore, but saturates above it at U − U c1 ϳ T c Ӷ⌬ 0 . Also the biparticle channel acquires a finite threshold U c2 = W 2 ϳ T c Ӷ⌬ 0 at the energy of the 2 phase soliton.

Comparison of phase slippage processes in Josephson junctions and charge-density wave stacked junctions

“…Both pictures show the space periodicity, L, between phase slippage events. A theory of phase decoupling induced by voltage V on the junction [5,7] gives the relationship between the V and L…”

Multi-Fluid Hydrodynamics in Charge Density Waves with Collective, Electronic, and Solitonic Densities and Currents

“…We shall consider the kinematics at presence of moving dislocation lines or loops by adopting to CDWs [7,19] the prescriptions [43,44] of the continuous theory of dislocations. At presence of vortices the local deformations and velocities ω j , j = x, y, z, t, are not derivatives of the same phase ϕ: ω = ∇ϕ if dislocations are present and moreover ω t = ∂ t ϕ if they also move:…”

“…The phase solitons [13,14,15] viewed as interstitials/vacancies of the CDW considered as a crystal of electronic pairs, provide a material for the climb of dislocations required for their expansion. The dislocations participate in depinning, in generation of coherent signals by a sequence of phase-slip events [16,17], in structures at contacts and junctions [18,19,20]. Generation of intrinsic defects via sliding over the host lattice imperfections gives a clue [21,22,23] to observed nonlinear current-voltage characteristics.…”

Solitons and Their Arrays: From Quasi 1D Conductors to Stripes

“…They include: two principle limits of electronic concentration (small and nearly half [18] band fillings); arbitrary filling with effects of breaking charge conjugation symmetry [19];…”