Comment on “Essence of intrinsic tunneling: Distinguishing intrinsic features from artifacts”

Abstract

In a recent paper V.Zavaritsky has argued that interlayer (c− axis) current-voltage characteristics of high temperature superconductors (HTSC) are Ohmic, and has claimed to disprove all findings of intrinsic tunnelling spectroscopy, as well as existence of the interlayer tunnelling and the intrinsic Josephson effect in HTSC, as such.In this comment I demonstrate, that the genuine interlayer current-voltage characteristics are strongly non-Ohmic, which undermines the basic postulate and the logical construction of the criticized paper. [6,7,8,13,14]. The latter experiments explicitly confirmed the correspondence between the stacking periodicity of intrinsic Josephson junctions (IJJ's) and the crystallographic unit cell of Bi-2212. The interlayer tunnelling was also successfully employed for intrinsic tunnelling spectroscopy, which is unique in it's ability to probe bulk phonon [15] and quasiparticle [13,16,17,18,19,20,21] The latter statement together with the assumption of semiconducting T −dependence of the Ohmic resistance leads in the presence of self-heating to non-linear IVC's, which according to Ref. [22] provides both qualitative and quantitative description of all key findings of interlayer transport experiments in HTSC, proves that all the non-linear features of interlayer IVC's are artifacts of selfheating and disproves all findings of intrinsic tunnelling spectroscopy.The incorrectness of the first postulate in the face of overwhelming and unambiguous experimental evidence [5,6,7,8,9,10,11,12,13,14,15] does not require extra comments, except that it demonstrates an obvious failure of the reviewing process in several scientific journals.In this comment I demonstrate incorrectness of the second postulate. It is shown that the genuine interlayer IVC's of Bi-2212 are strongly non-Ohmic and are represented by perfectly periodic, multibranch IVC's, which are not affected by self-heating. The huge, two order of magnitude, genuine non-linearity of IVC's represents the extent of irrelevance of the model advocated by Zavaritsky to the essence of intrinsic tunnelling in HTSC and undermines the logical construction of Ref. [22].Intrinsic tunnelling characteristics of HTSC mesa structures exhibit a characteristic multi-branch structure due to one-by one switching of IJJ's from the superconducting into the resistive state [5]. Each time a new junction is switched into the resistive state the dissipation power within the mesa increases and the effective temperature of the mesa rises as a result of self-heating [24]:where P = V I is the total dissipation power and R th is the effective thermal resistance of the mesa, which depend on the sample geometry and temperature [24,25]. The progressive self-heating with the branch number may result in a systematic distortion of the IVC in the way, shown in Fig. 1. Namely, the critical current and the separation between branches decrease with the branch number. At large P , significant self-heating is indicated by progressive back-bending of the branches. Fig. 1 shows how th...

Pseudogap behavior revealed in interlayer tunneling in overdopedBi2Sr2CaCu2O8+xBae1, Park2, Choi3 et al. 2008Phys. Rev. B153260View full textAdd to dashboardCite

“…Since the ITS is sensitive to bias-induced self-heating, extreme care should be taken, as in this study, to keep the sample temperature constant within a tolerance limit over the whole bias sweeping range. However, as demonstrated by Krasnov et al, 16,43 most of the essential observations on a PG feature remain valid even in the earlier ITS results. Thus, ITS, with a precautious measure taken to eliminate self-heating, should provide a very useful experimental tool to investigate the electronic excitation spectrum of highly anisotropic materials containing naturally grown tunneling junctions.…”

Comment on “Counterintuitive consequence of heating in strongly-driven intrinsic junctions ofBi2Sr2CaCu2O8+δm

“…iii) Direct measurement of mesa temperatures for small ITS mesas showed that at the peak T m remains well below T c [9] [1] . Recently this conclusion was confirmed by "intrinsic" detection of T m [2,3]. In this case, T −dependent characteristics of the mesa itself were used for determination of T m , avoiding any possible lag between the mesa and the thermometer.…”

“…Self-heating in ITS is actively discussed [2] for more than a decade (see Ref. [3] for a recent summary).…”

Temperature distribution in large Bi2212 mesas

“…The postulate that the self-heating is the only origin of the I-V non-linearities [35] does not stand up well to the following qualitative and simple reasoning (see also other arguments in Ref. [36]).…”