Abstract
Forcing systems through fast non-equilibrium phase transitions offers the opportunity to study new states of quantum matter that self-assemble in their wake. Here we study the quantum interference effects of correlated electrons confined in monolayer quantum nanostructures, created by femtosecond laser-induced quench through a first-order polytype structural transition in a layered transition-metal dichalcogenide material. Scanning tunnelling microscopy of the electrons confined within equilateral triangles, whose dimensions are a few crystal unit cells on the side, reveals that the trajectories are strongly modified from free-electron states both by electronic correlations and confinement. Comparison of experiments with theoretical predictions of strongly correlated electron behaviour reveals that the confining geometry destabilizes the Wigner/Mott crystal ground state, resulting in mixed itinerant and correlation-localized states intertwined on a length scale of 1 nm. The work opens the path toward understanding the quantum transport of electrons confined in atomic-scale monolayer structures based on correlated-electron-materials.
Highlights
Forcing systems through fast non-equilibrium phase transitions offers the opportunity to study new states of quantum matter that self-assemble in their wake
The equilateral triangles (ETs) structures (Fig. 1f) are created by a controlled exposure of a freshly exfoliated 1T-TaS2 single crystal to laser pulses in ultrahigh vacuum at 80 K22, where the majority of the top surface is transformed to the 1H polytype, but ET structures of 1T polytype remain structurally unchanged[23,24]
At 80 K, where the measurements are preformed, the 1H polytype is metallic, while the 1T polytype is nominally in the insulating commensurate charge-density-wave (CCDW) phase14. (For reference, low-temperature scans showing the appearance of the 3 × 3 CDW of the 1T layer are shown in the Supplementary information)
Summary
Forcing systems through fast non-equilibrium phase transitions offers the opportunity to study new states of quantum matter that self-assemble in their wake. The domains have atomically defined sides parallel to the crystal axes of the 1T layer, matching the lattice structure of the surrounding 1H layer, forming a perfect ET shape with edges at 60° to each other (Fig. 1a, b). A remarkable feature of these ETs, well visible in the R structure in Fig. 2e is the nontrivial QI pattern in the corner which does not fit the CCDW order.
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