Local nature of charge-density-wave conduction noise in niobium triselenide

Ong, Nai Phuan; Verma, G.

doi:10.1103/physrevb.27.4495

Cited by 56 publications

(18 citation statements)

References 11 publications

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“…[21][22][23][24] This is due to the fact that the electric field component along the chains is inhomogeneous and different currents flow in the different parts of the sample. 24 However, all the frequencies of the NBN peaks reported there increased with increasing current. As far as we know, there is no report that the NBN peaks decrease in frequency as the total current I is increased.…”

Section: Discussionmentioning

confidence: 98%

“…Actually, only one series of the sharp periodic peaks was observed and their frequencies linearly increase as a function of ͑I − I T 0 ͒, suggesting that the part of the sample in which the NBN measurements were done has a homogeneous threshold electric field E T and the SDW with a long correlation length is formed in this part. In the NBN spectra of the inhomogeneous CDW systems [21][22][23][24] several series of the fundamental and harmonics were observed. When the homogeneity becomes worse, it may be difficult to observe the NBN spectrum.…”

Section: A Nbn In Sample P56mentioning

confidence: 92%

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Sliding spin-density wave in(TMTSF)2PF6studied with narrow-band noise

et al. 2004

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We report narrow-band noise (NBN) due to sliding motions of the spin-density wave (SDW) condensate at 2.0 K in three samples of ͑TMTSF͒ 2 PF 6 and the magnetic-field effects. Typical NBN spectra coming from the saw-toothed-wave current oscillations are clearly observed. The periodic peaks due to the 4k F -charge-density wave (CDW) collective excitation are found, together with the SDW moving with a faster velocity, revealing that the sliding mode of the SDW is coupled with 4k F -CDW fluctuations. Observation of the interference peaks gives evidence of spatially nonuniform dc current carried by the deformable SDW in domains. At large currents the NBN spectrum drastically changes with increasing current and depends on applied magnetic field, suggesting a dynamical phase transition from the plastic-flow phase to the moving-solid phase. In the movingsolid phase the frequencies of the periodic peaks decrease with increasing current because the spatial coherency grows rapidly. The current oscillations in this phase are interpreted in terms of the coexistence of the 2k F -CDW collective excitation with the phason.

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Section: Discussionmentioning

confidence: 98%

Section: A Nbn In Sample P56mentioning

confidence: 92%

Sliding spin-density wave in(TMTSF)2PF6studied with narrow-band noise

et al. 2004

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“…For example, in a recent experiment 10 it was shown that voltage probes attached with silver paint partition the sample into three segments that oscillate independently. It was proposed that at low E the portion of the sample covered by the paint remains pinned while the uncovered portion slides.…”

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confidence: 98%

Vortex-Array Model for Charge-Density-Wave Conduction Noise

1984

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It is proposed that ac voltage (^a c ) oscillations observed in sliding charge-density-wave systems are caused by phase vortices at the sample ends. The model's prediction that v ac is length independent is verified experimentally. The long-range phase coherence implied by thermal-gradient experiments is consistent with the vortex model but not with models based on impurities.PACS numbers: 72.15.Nj, 72.20.Ht,One of the most puzzling features of electronic transport in the series of compounds that demonstrate charge-density-wave (CDW) conduction is the appearance of well defined voltage oscillations 1 when the dc electric field exceeds a threshold value E T . The fundamental frequency of this oscillation has been shown 2 to be proportional to the current carried by the moving CDW. This phenomenon has been seen 3 in NbSe 3 , TaS 3 , (TaSe 4 ) 2 I, (NbSe 4 ) 10 / 3 I, and the bronzes K 0 . 3 MoO 3 and Rb 0 . 3 MoO 3 , all of which display nonlinear I-V curves associated with CDW depinning. Most of the theories 4 ' 6 proposed for the ac voltage invoke the impurities as the source of the current oscillations through their interaction with the moving CDW. The simplest such model is the impurity washboard model of Gruner, Zawadowski, and Chaikin. 4 In the static situation the weakly pinned condensate distorts its phase to maximize the pinning energy gained from the impurities. The average length of the domains within which the phase is roughly uniform is the Fukuyama-Lee-Rice (FLR) 7 length X FLR (10-50 Mm in NbSe 3 ). It is well established experimentally that the threshold field is determined by the impurity concentration. However, the situation when the CDW moves is less clear. In particular we shall present evidence showing that the phase coherence length (when sliding) is much longer than A FLR and infer that the impurities play no major role in the (narrow-band) noise generation. (A perplexing problem with domain structures in the sliding CDW is the question of how oscillations in adjacent domains couple to provide the sharp spectra seen. Also the question of what happens at walls separating domains with different velocities is unresolved.)We propose a model for the CDW noise based on the following assumptions: (I) An array of vortices is created when the CDW phase undergoes an abrupt change such as at the sample ends. (II) Regardless of the phase configuration in the static (pinned) condensate, when sliding occurs the phase coherence may extend over macroscopic distances approaching the sample length in pure samples. The creation and annihilation of the phase vortices at the sample ends leads to a modulation of the current which is observed as the ac noise. Various theories 8 ' 9 have explored the effect of internal degrees on the dynamics of the moving CDW. In our model we may regard the conduction noise as a manifestation of the internal degrees of freedom expressed as phase dislocations in inhomogeneous situations. The vortex array insofar as it is an energetically favorable way for the system to overcome ph...

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“…Other mechanisms of the narrow band noise have also been proposed by Portis [185] and Barnes and Zawadowski [204]. We also note that Ong et al [205,206] have recenrly claimed that the noise phenomena are not a bulk effect, but they are observed only in the inhomogeneous region in a sampie ne ar the contact to leads.…”

Section: Noise Associated With the Non-ohmic Conductivitymentioning

confidence: 76%