Ultrafast non-thermal and thermal switching in charge configuration memory devices based on 1T-TaS2

Abstract

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.

Charge Configuration Memory Devices: Energy Efficiency and Switching Speed

“…The entire measurement cycle is shown starting from 280 K, cooling and switching at 350 mK by a single write (W) pulse, and heating back to 280 K, where the system reverts to its original state. Upon heating we observe characteristic steps, previously attributed to relaxation of domains. , The insert to Figure a shows the R – T curves on an expanded scale, showing a commonly observed hysteresis associated with the presence of additional phases , above 100 K.…”

“…The write (W) cycle of the CCM device was shown to be nonthermal, while the erase (E) cycle is at least partially thermal. 7 Intrinsic nonohmic behavior and dissipation at the contacts, 12 especially if energy barriers are formed as a result of interface chemistry, may limit the energy efficiency in small devices. 13 In this paper we investigate CCM scaling properties in the nonvolatile resistance switching region, which is particularly relevant for incorporation into cryocomputing environments where the device has potential applications.…”

“…Unfortunately, the direct coupling of an electronic two-level system to lattice degrees of freedom causes rapid state decoherence and dissipation, which fundamentally limits charge-storage based memory concepts. As an apparent solution to this problem, it was shown recently that topological protection that stabilizes different charge density wave (CDW) domain states in the quasi-2D layered transition metal chalcogenide 1T-TaS 2 can be used for memory devices. , The basic mechanism for such a charge configuration memory (CCM) was shown to be unique to this material, − involving reversible charge reconfiguration from an insulating, spatially uniform CDW state to a metallic domain state with accompanying restacking of the CDW along the direction perpendicular to the layers . To develop the CCM concept into viable practical devices, a better understanding of the device characteristics is required, particularly the operational limitations, such as write speed, energy efficiency, and endurance, as well as size scaling limitations and contact material compatibility.…”

“…For low temperature operation, minimization of dissipation is essential, so investigation of how the switching energy scales with device size is particularly important. The write (W) cycle of the CCM device was shown to be nonthermal, while the erase (E) cycle is at least partially thermal . Intrinsic nonohmic behavior and dissipation at the contacts, especially if energy barriers are formed as a result of interface chemistry, may limit the energy efficiency in small devices .…”

Photo-induced Hidden Phase of 1T-TaS2 with Tunable Lifetime

“…However, novel phases of matter may arise due to non-equilibrium between the various sub-systems (electron, lattice, spin...) of a material. In particular, the use of ultrafast lasers as a driving source allows reaching these non-ergodic conditions and driving matter to novel phases [6][7][8][9][10][11][12][13][14][15]. This approach is particularly useful to investigate strongly correlated materials, where the competition between the different phenomena ruling the phase of a material can be modified, leading to the emergence of new phases.…”