Mesoscopic irregularly ordered and even amorphous self-assembled electronic structures were recently reported in two-dimensional metallic dichalcogenides (TMDs), created and manipulated with short light pulses or by charge injection. Apart from promising new all-electronic memory devices, such states are of great fundamental importance, since such aperiodic states cannot be described in terms of conventional charge-density-wave (CDW) physics. In this paper, we address the problem of metastable mesoscopic configurational charge ordering in TMDs with a sparsely filled charged lattice gas model in which electrons are subject only to screened Coulomb repulsion. The model correctly predicts commensurate CDW states corresponding to different TMDs at magic filling fractions = / / / / / f 1 3, 1 4, 1 9, 1 13, 1 16.mDoping away from f m results either in multiple neardegenerate configurational states, or an amorphous state at the correct density observed by scanning tunnelling microscopy. Quantum fluctuations between degenerate states predict a quantum charge liquid at low temperatures, revealing a new generalized viewpoint on both regular, irregular and amorphous charge ordering in transition metal dichalcogenides.

Charge configuration memory (CCM) device operation is based on the controllable reconfiguration of electronic domains in a charge-density-wave material. Since the dominant effect involves the manipulation of electrons rather than atoms, the devices can display sub-picosecond switching speed and ultralow, few femtojoule switching energy. The mechanisms involved in switching between domain states of different electrical resistances are highly non-trivial and involve trapping non-equilibrium charges within topologically protected domain states. Here, we discuss the underlying physics that are deemed essential for the operation of CCM devices, focusing on the unusual asymmetry between non-thermal “write” processes and thermal “erase” processes from the point of view of the mechanism in relation to the thermal dynamics.

Current trends in data processing have given impetus for an intense search of new concepts of memory devices with emphasis on efficiency, speed, and scalability. A promising new approach to memory storage is based on resistance switching between charge-ordered domain states in the layered dichalcogenide 1T-TaS 2 . Here we investigate the energy efficiency scaling of such charge configuration memory (CCM) devices as a function of device size and data write time τ W as well as other parameters that have bearing on efficient device operation. We find that switching energy efficiency scales approximately linearly with both quantities over multiple decades, departing from linearity only when τ W approaches the ∼0.5 ps intrinsic switching limit. Compared to current state of the art memory devices, CCM devices are found to be much faster and significantly more energy efficient, demonstrated here with two-terminal switching using 2.2 fJ, 16 ps electrical pulses.