title: Subgap collective tunneling and its staircase structure in charge density waves.
abstract: Tunneling spectra of chain materials NbSe3 and TaS3 were studied in nanoscale mesa devices. Current-voltage I-V characteristics related to all charge density waves (CDWs) reveal universal spectra within the normally forbidden region of low V, below the electronic CDW gap 2Delta. The tunneling always demonstrates a threshold Vt approximately 0.2Delta, followed, for both CDWs in NbSe3, by a staircase fine structure. T dependencies of Vt(T) and Delta(T) scale together for each CDW, while the low T values Vt(0) correlate with the CDWs' transition temperatures Tp. Fine structures of CDWs perfectly coincide when scaled along V/Delta. The results evidence the sequential entering of CDW vortices (dislocations) in the junction area with the tunneling current concentrated in their cores. The subgap tunneling proceeds via the phase channel: coherent phase slips at neighboring chains.
authors.affiliation: IRE RAS, Mokhovaya 11-7, 101999 Moscow, Russia.
authors.forename: Yu I
authors.initials: YI
authors.lastname: Latyshev
authors.forename: P
authors.initials: P
authors.lastname: Monceau
authors.forename: S
authors.initials: S
authors.lastname: Brazovskii
authors.forename: A P
authors.initials: AP
authors.lastname: Orlov
authors.forename: T
authors.initials: T
authors.lastname: Fournier