Terahertz-field-induced insulator-to-metal transition in vanadium dioxide metamaterial

Abstract

Electron-electron interactions can render an otherwise conducting material insulating, with the insulator-metal phase transition in correlated-electron materials being the canonical macroscopic manifestation of the competition between charge-carrier itinerancy and localization. The transition can arise from underlying microscopic interactions among the charge, lattice, orbital and spin degrees of freedom, the complexity of which leads to multiple phase-transition pathways. For example, in many transition metal oxides, the insulator-metal transition has been achieved with external stimuli, including temperature, light, electric field, mechanical strain or magnetic field. Vanadium dioxide is particularly intriguing because both the lattice and on-site Coulomb repulsion contribute to the insulator-to-metal transition at 340 K (ref. 8). Thus, although the precise microscopic origin of the phase transition remains elusive, vanadium dioxide serves as a testbed for correlated-electron phase-transition dynamics. Here we report the observation of an insulator-metal transition in vanadium dioxide induced by a terahertz electric field. This is achieved using metamaterial-enhanced picosecond, high-field terahertz pulses to reduce the Coulomb-induced potential barrier for carrier transport. A nonlinear metamaterial response is observed through the phase transition, demonstrating that high-field terahertz pulses provide alternative pathways to induce collective electronic and structural rearrangements. The metamaterial resonators play a dual role, providing sub-wavelength field enhancement that locally drives the nonlinear response, and global sensitivity to the local changes, thereby enabling macroscopic observation of the dynamics. This methodology provides a powerful platform to investigate low-energy dynamics in condensed matter and, further, demonstrates that integration of metamaterials with complex matter is a viable pathway to realize functional nonlinear electromagnetic composites.

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

“…Preliminary tests show that driving such large-area trilayers with intense laser pulses easily yields THz pulses with peak fields of several 100 kV cm -1 which exceed those obtained with more strongly pumped large-area ZnTe emitters 50 . Therefore, spintronic THz sources exhibit a high potential for enabling nonlinear-optical studies 51,52 in the difficult-to-access region between 5 and 10 THz. More generally, our results highlight metallic magnetic multilayers as a new and very promising class of high-performance and broadband THz emitters.…”

Towards properties on demand in quantum materials

“…For example, intense THz fields 44 in the range 10 6 -10 7 V cm -1 can be generated across a broad swath of the electromagnetic spectrum to drive quantum phases at their natural energy scales. The electric field can be further enhanced by integrating quantum materials with metamaterials 45 . The strength of the perturbing electric field is a key enabler in dynamic materials control research.…”

“…The strength of the perturbing electric field is a key enabler in dynamic materials control research. For example, strong, high-frequency fields can initiate phase transitions, including the insulator-to-metal transition 45 (discussed in 'Revealing hidden phases and new states of matter') or drive nonlinear effects such as on-resonance parametric amplification and high harmonic generation 46,47 . Sub-gap electromagnetic The tenet of dressed states is central to the physics of quantum materials.…”

Spatially resolved ultrafast magnetic dynamics initiated at a complex oxide heterointerface

“…Switching has also been demonstrated in these materials using femtosecond optical excitation, at near-visible [9,10,11,12,13,14,15], mid-infrared [16,17,18,19,20], or THz [21,22,23] wavelengths.…”