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.

First-Order Character and Observable Signatures of Topological Quantum Phase Transitions / Amaricci, Adriano; Budich, J. C.; Capone, Massimo; Trauzettel, B.; Sangiovanni, Giorgio. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 114:18(2015), pp. 1-5. [10.1103/PhysRevLett.114.185701]

First-Order Character and Observable Signatures of Topological Quantum Phase Transitions

Amaricci, Adriano;Capone, Massimo;Sangiovanni, Giorgio
2015-01-01

Abstract

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.
2015
114
18
1
5
185701
https://arxiv.org/abs/1411.7390v2
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.185701
Amaricci, Adriano; Budich, J. C.; Capone, Massimo; Trauzettel, B.; Sangiovanni, Giorgio
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/12617
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