Topological quantum phase transitions are characterized by changes in global topological invariants. These invariants classify many-body systems beyond the conventional paradigm of local order parameters describing spontaneous symmetry breaking. For noninteracting electrons, it is well understood that such transitions are continuous and always accompanied by a gap closing in the energy spectrum, given that the symmetries protecting the topological phase are maintained. Here, we demonstrate that a sufficiently strong electron-electron interaction can fundamentally change the situation: we discover a topological quantum phase transition of first-order character in the genuine thermodynamic sense that occurs without a gap closing. Our theoretical study reveals the existence of a quantum critical endpoint associated with an orbital instability on the transition line between a 2D topological insulator and a trivial band insulator. Remarkably, this phenomenon entails unambiguous signatures related to the orbital occupations that can be detected experimentally.
|Titolo:||First-Order Character and Observable Signatures of Topological Quantum Phase Transitions|
|Autori:||Amaricci, A.; Budich, J.C.; Capone, M.; Trauzettel, B.; Sangiovanni, G.|
|Rivista:||PHYSICAL REVIEW LETTERS|
|Data di pubblicazione:||2015|
|Digital Object Identifier (DOI):||10.1103/PhysRevLett.114.185701|
|Appare nelle tipologie:||1.1 Journal article|