Ultrafast switching to a stable hidden topologically protected quantum state in an electronic crystal

L. Stojchevska 1, 2 I. Vaskivskyi 1 T. Mertelj 1 P. Kusar 1 D. Svetin 1 S. Brazovskii 3, 4 D. Mihailovic 1, 2, 5

Science, American Association for the Advancement of Science, 2014, 344, pp.177-180

Hidden states of matter with novel and unusual properties may be created if a system out of equilibrium can be induced to follow a trajectory to a state which is inaccessible or does not even exist under normal equilibrium conditions. Here we report on the discovery of a hidden (H) topologically protected electronic state in a layered dichalcogenide 1T-TaS2 crystal reached as a result of a quench caused by a single 35 fs laser pulse. The properties of the H state are markedly different from any other state of the system: it exhibits a large drop of electrical resistance, strongly modified single particle and collective mode spectra and a marked change of optical reflectivity. Particularly important and unusual, the H state is stable for an arbitrarily long time until a laser pulse, electrical current or thermal erase procedure is applied, causing it to revert to the thermodynamic ground state. Major observed events can be reproduced by a kinetic model describing the conversion of photo excited electrons and holes into an electronically ordered crystal, thus converting a Mott insulator to a conducting H state. Its long-time stability follows from the topological protection of the number of periods in the electronic crystal.

  • 1. Department of Complex Matter
  • 2. Jozef Stefan International Postgraduate School
  • 3. LPTMS - Laboratoire de Physique Théorique et Modèles Statistiques
  • 4. International Institute of Physics
  • 5. CENN Nanocenter