Avalanche breakdown in GaTa4Se8−xTex narrow-gap Mott insulators

Abstract

Mott transitions induced by strong electric fields are receiving growing interest. Recent theoretical proposals have focused on the Zener dielectric breakdown in Mott insulators. However, experimental studies are still too scarce to conclude about the mechanism. Here we report a study of the dielectric breakdown in the narrow-gap Mott insulators GaTa 4 Se 8 À x Te x . We find that the I-V characteristics and the magnitude of the threshold electric field (E th ) do not correspond to a Zener breakdown, but rather to an avalanche breakdown. E th increases as a power law of the Mott-Hubbard gap (E g ), in surprising agreement with the universal law E th pE g 2.5 reported for avalanche breakdown in semiconductors. However, the delay time for the avalanche that we observe in Mott insulators is over three orders of magnitude greater than in conventional semiconductors. Our results suggest that the electric field induces local insulator-to-metal Mott transitions that create conductive domains that grow to form filamentary paths across the sample.

Field-Driven Mott Gap Collapse and Resistive Switch in Correlated Insulators

“…Remarkably, these experiments ubiquitously report a whole novel scenario for the electric breakdown that cannot be reconciled with the standard Landau-Zener description. For instance, the breakdown occurs through the abrupt formation of a conductive channel at anomalously small threshold fields [5], as opposed to the smooth activation at fields of the order of the gap as predicted by across-gap tunnelling. In addition, VO 2 electric double layer transistors formed at a solid/electrolyte interface show massive conducting channels that suddenly open up above a threshold gate-voltage, with an extension much beyond the fundamental electrostatic screening length [13,14].…”

“…Motivated by the strong evidence that the first-order character of the Mott transition plays a major role in the aforementioned experiments [5,6,13], in this Letter we explore the route to the electric breakdown that opens whenever a stable Mott insulator coexists with a metastable metal which is not connected to the insulating solution.…”

“…[5,6] and modelled phenomenologically through a resistor network mimicking the competition between a stable insulating phase and a metastable metallic one. Nonetheless a true microscopic description in model Mott insulators is still lacking.…”

Universal mechanism of tetrahedral metal cluster formation in structures with breathing pyrochlore sublattices

“…Recently, several correlation effects have been reported for AB 4 X 8 lacunar spinels, including pressure-induced superconductivity [35], bandwidth-controlled metal-to-insulator transition [36,37], large negative magnetoresistance [38], a two-dimensional topological insulating state [39], resistive switching through electric field-induced transition [40][41][42], emergence of orbitally driven ferroelectricity [43], and an extended Néel-type skyrmion phase [44].…”

Spin waves in the fcc lattice antiferromagnet: competing interactions, frustration, and instabilities in the Hubbard model

“…Antiferromagnetic (AF) orders in fcc materials range from type-III and type-I in the 1:2 compounds MnS 2 and MnTe 2 , 2 to type-II in the 1:1 compound MnO. 3 Magnetic frustration and pressure-induced metal-insulator transition are exhibited by a variety of complex compounds having effective fcc magnetic lattice such as alkali fullerides A 3 C 60 (A = K, Rb, Cs), 4,5 cluster compounds GaTa 4 Se 8 , GaNb 4 Se 8 , 6 and 'B site ordered' double perovskites. 7 Magnetic frustration in an itinerant electron model has additional features besides the usual geometric frustration effect in the ideal Heisenberg model with nearest-neighbor (NN) two-spin interaction where the interplay of magnetic interactions and lattice geometry results in frustrated spins.…”