Abstract
Recent demonstrations of controlled switching between different ordered macroscopic states by impulsive electromagnetic perturbations in complex materials have opened some fundamental questions on the mechanisms responsible for such remarkable behavior. Here we experimentally address the question of whether two-dimensional (2D) Mott physics can be responsible for unusual switching between states of different electronic order in the layered dichalcogenide 1T-TaS2, or it is a result of subtle inter-layer “orbitronic” re-ordering of its stacking structure. We report on in-plane (IP) and out-of-plane (OP) resistance switching by current-pulse injection at low temperatures. Elucidating the controversial theoretical predictions, we also report on measurements of the anisotropy of the electrical resistivity below room temperature. From the T-dependence of ρ⊥ and ρ||, we surmise that the resistivity is more consistent with collective motion than single particle diffusive or band-like transport. The relaxation dynamics of the metastable state for both IP and OP electron transport are seemingly governed by the same mesoscopic quantum re-ordering process. We conclude that 1T-TaS2 shows resistance switching arising from an interplay of both IP and OP correlations.
Highlights
In the absence of systematic transport measurements and electronic structure along the c axis, the issue of OP interactions, and the importance of the IP correlations remain unresolved
1T-TaS2 has recently attracted further attention because it was shown to exhibit sub-35 fs photo-induced[15] resistance switching to a hidden (H) CDW state, with similar behavior induced by 40 ps electrical pulse-injection[16]
Recent reports of gate-tunable state switching to a supercooled NC state at low T17,18 and dynamical resistance switching[19] are indicative of the existence of multiple competing orders at low temperature
Summary
Ritschel et al.[10] considered the simpler effect of two possible stackings Ts = 2aC +cC and Ts =cC, where aC and cC are the distorted unit cell vectors in the C state, considering random bi-layer stacking along the three equivalent vectors (2aC +cC, 2bC +cC and −(aC +bC) +cC) Their band structure calculations for cC stacking predict an IP gap and metallic behavior along the c axis due to a single band crossing the Fermi level along the Γ−A direction. In the region 40–140 K, the observed activation energy (EA ≈ 91K IP and 112 K OP) is far too small to be related to the Mott or CDW gaps whose values are at least 0.1 eV37, perhaps closer to 0.3 eV10 This energy scale EA is not seen in any excitations which are measured by optical absorption, photoemission or tunneling. Considering that the largest change of lattice constant upon CDW re-ordering from the NC to the ( ) C state is in the c direction
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