Quantum billiards with correlated electrons

Our collaborators at the Jozef Stefan Institute – the leading author, Jan Ravnik, is now a PSI Fellow at LMN – report a study of the electron ordering in equilateral triangle structures via photoexcitation of the prototypical dichalcogenide 1T-TaS₂.

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 study of Jan Ravnik and collaborators, published in Nature Communications, reports on quantum interference effects of correlated electrons confined in monolayer nanostructures in the layered transition-metal dichalcogenide material 1T-TaS₂.

Equilateral triangle nanostructures are created by femtosecond laser-induced quenches through a first-order polytype structural transition. Scanning tunnelling microscopy of the electrons confined within the equilateral triangles, whose dimensions are a few tens of crystal unit cells, 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 localized states which are intertwined on nm length scales.  The work opens the path towards understanding quantum transport of correlated electrons confined in atomic-scale monolayer structures.

The experiments were conducted in the group of Prof. Dragan D. Mihailović at the Jozef Stefan Institute in Ljubljana, Slovenia, with which LMN has established a collaboration on transition metal chalcogenides aiming to investigate the materials at PSI's accelerator-based photon sources and fabricate efficient ultrafast memory devices.

The research work was highlighted in a video (english) by the Slovenian press agency.