Mott Memory and Neuromorphic Devices

Abstract

| Orbital occupancy control in correlated oxides allows the realization of new electronic phases and collective state switching under external stimuli. The resultant structural and electronic phase transitions provide an elegant way to encode, store, and process information. In this review, we examine the utilization of Mott metal-to-insulator transitions, for memory and neuromorphic devices. We emphasize the overarching electron-phonon coupling and electron-electron interaction-driven transition mechanisms and kinetics, which renders a general description of Mott memories from aspects such as nonvolatility, sensing scheme, read/write speed, and switching energy. Various memory and neuromorphic device architectures incorporating phase transition elements are reviewed, focusing on their operational principles. The role of Peierls distortions and crystal symmetry changes during phase change is discussed. Prospects for such orbitronic devices as hardware components for information technologies are summarized.

Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission

“…Around 67-68 • C, the vanadium dioxide undergoes the electronic metal-insulator transition upon heating or cooling with hysteretic behavior and a change in the electrical conductivity by several orders of magnitude, coupled to a Structural Phase Transition (SPT) from the monoclinic to the rutile phase. Since the discovery of the MIT transition more than 50 years ago by Morin and Westman [1,2], VO 2 has attracted a lot of interest because of its strong electron correlation; recently the interest has increased because of the wide number of different possible applications in optics, as detectors or sensors, and in novel memory devices based on the occurrence of the reversible MIT transition [5][6][7][8][9][10][11]. However, since its discovery, and even now, the nature of this electronic/structural transition remains an open question.…”

X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

“…Furthermore, coherent oxide/oxide heteroepitaxial film growth provides the opportunity to tailor these properties via biaxial strain [6]. In fact, ultra-thin films can support large percent level strains and are robust over millions of cycles through electronic-structural phase changes, both of which are known to cause fracturing in their bulk counterparts [7,8,9]. This makes this class of materials of great interest from both fundamental and technological perspectives.…”

“…Widely considered amongst the most suitable candidates for these technologies is vanadium dioxide [9,12,18,19]. VO 2 exhibits an abrupt and ultrafast MIT near room temperature that can be triggered by small, thermal [20,21], chemical [22], mechanical [23] and electrical [24,25] perturbations.…”

Complex Quasi-Two-Dimensional Crystalline Order Embedded in VO2 and Other Crystals

“…The insulating phase is structurally soft, as two other variants appear with doping or application of strain [5][6][7][8]. Although such materials are promising for applications (including lowdissipation logic [9][10][11] and many others), the lack of a microscopic theory has hindered progress. VO 2 is not alone: similar complex ordering also occurs in many other crystals [12][13][14][15], exhibiting diverse electronic and magnetic phases [16] whose properties would certainly reflect the intricacies of the underlying crystalline order.…”