The metal-insulator transition in disordered solids: How theoretical prejudices influence its characterization A critical review of analyses of experimental data

Abstract

In a recent experimental study, Siegrist et al. [Nature Materials 10, 202-208 (2011)] investigated the metal-insulator transition (MIT) induced by annealing in GeSb 2 Te 4 . The authors concluded that this phase-change material exhibits a discontinuous MIT with finite minimum metallic conductivity. The striking contrast between their work and reports on many other disordered substances from the last decades motivates the present in-depth study of the influence of the MIT criterion used on the character of the MIT derived.First, we discuss in detail the inherent biases of various approaches to locating the MIT. Second, reanalyzing GeSb 2 Te 4 data, we show that this material resembles other disordered solids to a large extent: according to a widely-used approach, its temperature dependences of the conductivity, s(T ), may likewise be interpreted in terms of a continuous MIT. Third, examining previous experimental studies of crystalline Si:As, Si:P, Si:B, Ge:Ga, CdSe:In, n-Cd 0:95 Mn 0:05 Se, Cd 0:95 Mn 0:05 Te 0:97 Se 0:03 :In, disordered Gd, and nanogranular Pt-C, we detect substantial problems in the interpretations of s(T ) in numerous studies which claim the MIT to be continuous: Evaluating the logarithmic derivative d ln s/d ln T highlights serious inconsistencies. In part, they are common to all such studies and seem to be generic, in part, they vary from experiment to experiment. Fourth, for four qualitatively different phenomenological models of the temperature and control parameter dependence of the conductivity, we present the respective flow diagrams of d ln s/d ln T. In consequence, the likely generic inconsistencies seem to originate from the MIT being discontinuous, in contradiction to most of the original interpretations.Because of the large number and diversity of the experiments considered, these inconsistencies provide overwhelming evidence against the common, localization theory motivated interpretations. The primary challenges now lie in improving measurement precision and accuracy, rather than in extending the temperature range, and in developing a microscopic theory which explains the seemingly generic features of d ln s/d ln T.

Electron effective mass and electronic structure in nonstoichiometric amorphous Indium Gallium Zinc Oxide films

“…The enhancement of resistivity with decreasing temperature below ∼150 K originates from weak localization effect [18][19][20] and electron-electron interaction effect [20][21][22][23][24][25], while the reduction of carrier concentration is also caused by the electron-electron interaction effect [24][25][26][27]. According to Möbius [28,29], the logarithmic derivative of the conductivity w = d ln σ/d ln T is more sensitive than the TCR and defines a more accurate and reliable criterion to distinguish between metallic and insulating behaviors. For film No.1 the value of w tends to be zero as T approaching to zero [see inset of Fig.…”

Influence of Nanoarchitecture on Charge Donation and the Electrical-Transport Properties in [(SnSe)1+δ][TiSe2]q Heterostructures

“…The behavior observed here suggests that a metal to nonmetal transition is occurring, in part driven by disorder, as carrier concentration is decreased. Further analysis looking at the derivatives of conductivity has been proposed by Möbius to determine the origin of the metal to nonmetal transition, but requires careful temperature equilibration before the transport properties are measured …”

“…Further analysis looking at the derivatives of conductivity has been proposed by Mobius to determine the origin of the metal to nonmetal transition, but requires careful temperature equilibration before the transport properties are measured. 75 Mobility values were calculated directly from the resistivity and Hall data at low temperatures where electrons dominate the transport behavior. The average mobility values in the lowtemperature regime are given in Table 2.…”

SmS/EuS/SmS Tri-Layer Thin Films: The Role of Diffusion in the Pressure Triggered Semiconductor-Metal Transition

“…The measured electrical resistance, in the semiconducting state, can thus be lower upon deposition at 400 °C compared to films deposited at lower temperature, in accordance with our results (Figure 6a,c). Future work will focus on studying the influence of (measurement) temperature on the electrical behavior of these alloyed thin films, as this will yield insight in the dynamics of the metal-insulator transition [38].…”