the S-Ta-S sheet rather than the sheet structure. 2H-TaS2 is a superconductor with the bulk transition temperature TC = 0.5 K, which increases to 2.2 K in flakes with a thickness of a few atomic layers. The bulk TC value increases up to ~8 K at 10 GPa and then saturates with increasing pressure. In contrast, 1T-TaS2 starts superconducting only at ~2 GPa; as a function of pressure its TC quickly rises up to 5 K at ~4 GPa and then saturates. At ambient pressure and low temperatures 1T-TaS2 is a Mott insulator. Upon heating it changes to a Triclinic charge density wave (TCDW) state at TTCDW ~ 220 K, to a nearly commensurate charge density wave (NCCDW) state at TNCCDW ~ 280 K, to an incommensurate CDW (ICCDW) state at TICCDW ~ 350 K, and to a metallic state at TM ~ 600 K. In the CDW state the TaS2 lattice deforms to create a periodic Star of David pattern. Application of (e.g. 50fs) optical laser pulses or voltage pulses (~2–3 V) through electrodes or in a scanning tunneling microscope (STM) to the CDW state causes it to drop electrical resistance and creates a "mosaic" or domain state consisting of nanometer-sized domains, where both the domains and their walls exhibit metallic conductivity. This mosaic structure is metastable and gradually disappears upon heating. Memory devices and other potential applications Switching of the material to and from the "mosaic", or domain state, by optical or electrical pulses is used for "Charge configuration memory" (CCM) devices. The distinguishing feature of such devices is that they exhibit very efficient and fast non-thermal resistance switching at low temperatures. Room temperature operation of a charge-density-wave oscillator and thermally-driven GHz modulation of the CDW state have been demonstrated. References Sulfides Tantalum compounds Transition metal dichalcogenides Monolayers