Whiskers of the quasi-one-dimensional conductor NbS3, phase II, have been synthesized. The samples show two charge-density wave (CDW) states: below 360 and below 150 K. Both CDWs show sharp threshold fields and coherent transport revealed by ac-dc coupling, i.e., Shapiro steps. The thinnest samples (cross sections below 104 nm2) exhibit Shapiro steps for frequencies at least as high as 4 GHz at room temperature. The results indicate that, for each of the CDW states, only one Nb chain per unit cell participates in the CDW transport.
In this work all the dessins d'enfant with no more than 4 edges are listed and their Belyi pairs are computed. In order to enumerate all dessins the technique of matrix model computations was used. The total number of dessins is 134; among them 77 are spherical, 53 of genus 1 and 4 of genus 2. The orders of automorphism groups of all the dessins are also found.Dessins are listed by the number of edges. Dessins with the same number of edges are ordered lexicographically by their lists of 0-valencies. The corresponding matrix model for any list of 0-valencies is given and computed. Complex matrix models for dessins with 1 -3 edges are used. For the dessins with 4 edges we use Hermitian matrix model, correlators for which are computed in [1].
Through transport, compositional and structural studies, we review the features of the chargedensity wave (CDW) conductor of NbS3 (phase II). We highlight three central results: 1) In addition to the previously reported CDW transitions at TP 1 = 360 K and TP 2 = 150 K, another CDW transition occurs at a much higher temperature TP 0 = 620-650 K; evidence for the non-linear conductivity of this CDW is presented. 2) We show that CDW associated with the TP 2 -transition arises from S vacancies acting as donors. Such a CDW transition has not been observed before. 3) We show exceptional coherence of the TP 1-CDW at room-temperature. Additionally, we report on the effects of uniaxial strain on the CDW transition temperatures and transport.
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