Subcycle insulator-to-metal transition in vanadium dioxide by terahertz-field-driven tunneling

TL;DR

This study demonstrates that intense terahertz electric fields can induce a rapid, metastable insulator-to-metal transition in vanadium dioxide through electronic tunneling, without lattice change, revealing new ultrafast phase control mechanisms.

Contribution

It introduces a novel method of triggering IMT in VO2 using terahertz fields via Zener tunneling, bypassing lattice transformations and enabling ultrafast phase manipulation.

Findings

Terahertz fields induce a full IMT via Zener tunneling.

The IMT occurs on a sub-picosecond timescale.

The method is applicable to other strongly correlated systems.

Abstract

In vanadium dioxide, the interplay between coherent lattice transformation and electronic correlation drives an insulator-to-metal transition (IMT). This phase commutation can be triggered by temperature, pressure, doping or deposition of optical energy. Here we demonstrate that an atomically-strong terahertz electric field initiates a metastable ultrafast IMT in vanadium dioxide without a concomitant lattice transformation. The free-space terahertz field acts as off-resonant excitation with photon energy below the lattice phonons and the interband transitions. Differently from optical and infrared excitation, terahertz interaction leads to a full IMT by interband Zener tunneling with a negligible entropy deposition. In previous experiments the temporal dynamics of IMT in VO2 could be only indirectly inferred. We disentangle the electronic and lattice contributions to the IMT on a sub-picosecond timescale. Near the critical temperature the IMT becomes dissipative and the terahertz field concludes the lattice-assisted metallic nucleation initiated by heating. The method of strong-field induced phase transition presented here is applicable to a wide class of strongly correlated systems and will enable the discovery of novel metastable phases.