Transitions between photoinduced macroscopic quantum states in 1T-TaS₂controlled by substrate strain

Abstract

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.

Controlling the metal-to-insulator relaxation of the metastable hidden quantum state in 1T-TaS 2

“…For both types of measurements, single crystals were deposited on sapphire, MgO, or quartz substrates by exfoliating with sticky tape and directly redepositing the exfoliated flakes onto the substrate. The substrate materials exert different tensile strain on the 1T-TaS 2 crystals upon cooling because of the mismatch of the lattice expansion between the sample and the substrates, the sapphire exerting a strain on the 1T-TaS 2 of ϵ = −0.19%, whereas the values for MgO and quartz are −0.13 and −0.03%, respectively, at 50 K ( 25 ). The thicknesses of the films deposited in this investigation are between 20 and 100 nm.…”

“… ( A ) A comparison of substrates with different tensile strain on a number of samples, also showing the sample-to-sample variation. The strain imposed by the sapphire, MgO, and quartz substrates at 50 K is 0.19, 0.13, and 0.03%, respectively ( 25 ). ( B ) A comparison for current and optical switching methods on sapphire.…”

Three-dimensional resistivity and switching between correlated electronic states in 1T-TaS2

“…Recent reports of gate-tunable state switching to a supercooled NC state at low T1718 and dynamical resistance switching19 are also indicative of the existence of multiple competing orders at low temperature. In the H state, the relaxation properties20 are strongly influenced by IP strain21, while sample thickness strongly influences the low-temperature electronic ordering17 confirming a strong susceptibility of the material to external perturbations along both IP and OP directions. Currently, the mechanism for switching, and the nature of the hidden state are hotly debated, which is closely linked to the controversial nature of the low-temperature commensurate ground state itself.…”

Possible strain induced Mott gap collapse in 1T-TaS2

“…Although the underlying mechanism of insulator-metal transition is still under debate, these controlled tuning methods are good candidates for the design of switching devices. Insightful information has been reported to tune the electronic states of complex materials by strain [26][27][28][29][30][31][32][33][34][35].…”