Manipulation and topological entanglement of fractionalized injected charge in the metastable state of 1T-TaS₂

Metastability of many-body quantum states is rare and poorly understood. An exceptional example of such a state is the low-temperature metallic state of the layered dichalcogenide 1T-TaS₂ in which metastable electronic order is frozen after external excitation. Here we investigate the microscopic dynamics of injected charges in the metastable state after photoexcitation or carrier injection in a multiple-tip scanning tunnelling microscope. Remarkably, carrier injection through electrodes and by low-fluence photoexcitation lead to similar structures, indicating a common mechanism. We observe the non-thermal formation of a topologically entangled network of dislocations in the electonic crystal superlattice, joined by domain walls. The annihilation of dislocations follows topological rules, which directly correlates with a change of macroscopic electrical resistance. At higher excitation fluences, an amorphous Wigner glass is formed, which is distinct from the fractionalized charged network forming at lower density.

Modelling charge injection in terms of a doped Wigner crystal reveals spatial charge fractionalization and entanglement, with observable non-locality. The emergent properties of the topologically entangled state are metastability and mesoscopic lattice distortions that govern the macroscopic transport properties of the system, and in particular the observed reversible non-thermal switching from insulator to metal. The topological fractionalization and entanglement also leads to robustness of the metastable state to external thermal perturbations. The possibility of manipulating topological entanglement of the created network suggests the way forward in the search for new metastable states in quantum many body systems.