The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density of electrons in transistors or by switching magnetic or ferroelectric order. Another possibility is switching between metallic and insulating phases by the motion of ions, but their speed is limited by slow nucleation and inhomogeneous percolative growth. Here we demonstrate fast resistance switching in a charge density wave system caused by pulsed current injection. As a charge pulse travels through the material, it converts a commensurately ordered polaronic Mott insulating state in 1T–TaS2 to a metastable electronic state with textured domain walls, accompanied with a conversion of polarons to band states, and concurrent rapid switching from an insulator to a metal. The large resistance change, high switching speed (30 ps) and ultralow energy per bit opens the way to new concepts in non-volatile memory devices manipulating all-electronic states.

Revealing the relaxation mechanisms of hidden states in transition metal dichalcogenides leads to control of metastability.

Controllable switching to and from metastable states of matter using electromagnetic fields could potentially revolutionize electronic logic and memory devices. Here, we investigate the effect of two-dimensional strain on switching between a photoinduced “hidden” state and a stable charge-ordered state in ultrathin 1T-TaS2 crystal films on different substrates, photoexcited by 35 fs laser pulses. The differential contraction of the sample and the substrate shows a very large and negative strain coefficient on the hidden state transition, implying that the stability of the hidden state could be markedly increased by tensile strain. Other transitions are not strongly affected by tensile strain.

The advancement of 3D-printing opens up a new way of constructing affordable custom terahertz (THz) components due to suitable printing resolution and THz transparency of polymer materials. We present a way of calculating, designing and fabricating a THz waveplate that phase-modulates an incident THz beam (λ0 = 2.14 mm) in order to create a predefined intensity profile of the optical wavefront on a distant image plane. Our calculations were performed for two distinct target intensities with the use of a modified Gerchberg-Saxton algorithm. The resulting phase-modulating profiles were used to model the polyactide elements, which were printed out with a commercially available 3D-printer. The results were tested in an THz experimental setup equipped with a scanning option and they showed good agreement with theoretical predictions.

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