Topological invariants, surface states, and interaction-driven phase transitions in correlated Kondo insulators with cubic symmetry

We show that the inclusion of nonlocal correlation effects in a variational wave function for the ground state of a topological Anderson lattice Hamiltonian is capable of describing both topologically trivial insulating phases and nontrivial ones characterized by an indirect gap, as well as its closure at the transition into a metallic phase. The method, though applied to an oversimplified model, thus captures the metallic and insulating states that are indeed observed in a variety of Kondo semiconductors, while accounting for topologically nontrivial band structures. PACS numbers: 71.27.+a, 71.30.+h, 03.65.Vf Introduction. Phenomena at the crossroads of topological insulators and strongly correlated systems have recently gained a lot of attention, mainly stimulated by theoretical proposals that the inclusion of strong correlations in specific models with a nontrivial topological content may give rise to novel and interesting phenomena [1][2][3][4][5]. However, electronic correlations in most of the discovered topological insulators [6,7] seem to be relatively weak, and hence of minor importance. For that reason, the concept of topological Kondo insulators (TKIs) originally put forward in Refs.[8] and [9] is particularly appealing due to its possible realization in already known Kondo insulating compounds [10]. Notably, SmB 6 is convincingly confirmed to be a TKI [11][12][13][14][15][16][17][18][19] with strong evidence of the essential role played by many-body correlations [20,21].Theoretically, the main physical properties of TKI are frequently described in the framework of topological Anderson lattice models in which strong spin-orbit coupling is encoded into a spin-dependent hybridization with odd parity in momentum space [8,9,22]. Many-body correlations in these models have been mostly treated by the slave-boson approach or by the dynamical mean-field theory (DMFT), and predicted to induce quantum phase transitions between topologically distinct bulk insulating phases [22][23][24].The aim of this work is to demonstrate that accounting for nonlocal spatial correlations, beyond those already well captured by the mentioned techniques, plays an important role in modeling TKIs. Specifically, those nonlocal correlations supply the f electron self-energy with a momentum dependence, which is otherwise purely local within DMFT and at the saddle point of the slave-boson theory. Remarkably, such a momentum dependence allows one to describe, above a critical interaction strength, the emergence of a topological Kondo insulator with an indirect gap, and its subsequent closure at the transition into a metallic state, an intriguing result opposite to the conventional Mott phenomenon where increasing interaction instead favours the onset of an insulating state. We disclose this scenario in two dimensions by means of the diagrammatic expansion of the Gutzwiller wave function (GWF) technique [25,26]. CeIrSb [35]). Moreover, assuming that increasing pressure roughly corresponds to reducing the interaction strength, we can ...

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confidence: 99%

Many-body breakdown of indirect gap in topological Kondo insulators

Wysokiński

Fabrizio

2016

“…A similar MF phase diagram was calculated in Ref. 's [17,18] for 3D TKIs, which did not consider the role of RKKY interactions.…”

Section: A Outlinementioning

confidence: 76%

Many-body effects in topological Kondo insulators

Iaconis

2015

We study the effect of interactions on the properties of a model 2D topological Kondo insulator phase. Loosely motivated by recent proposals where graphene is hybridized with impurity bands from heavy adatoms with partially filled d-shells, we introduce a model Hamiltonian which we believe captures the essential physics of the different competing phases. We show that there are generically three possible phases with different combinations of Kondo screening and magnetic order. Perhaps the most dramatic example of many-body physics in symmetry protected topological phases is the existence of the exotic edge states. We demonstrate that our mean field model contains a region with a time-reversal invariant bulk phase but where TR symmetry is spontaneously broken at the edge. Such a phase would not be possible in a non-interacting model. We also comment on the stability of this phase beyond mean field theory.

“…[52,53] where various tight-binding models of SmB 6 have been summarized and discussed, we consider a four band model described in Ref. [52,54] due to its simplicity. This model has been shown to reproduce energy dispersion from more complicated multi-band models, as well as the first principles calculations 52 .…”

Section: Two Dimensional Tci Phases In Tmki Thin Filmsmentioning

confidence: 99%

Interacting topological phases in thin films of topological mirror Kondo insulators

Zhang

Liu³

2016

We study the interaction effects on thin films of topological mirror Kondo insulators (TMKI), where the strong interaction is expected to play an important role. Our study has led to the following results: (1) We identify a rich phase diagram of non-interacting TMKI with different mirror Chern numbers in the monolayer and bilayer thin films; (2) We obtain the phase diagram with interaction and identify the regimes of interaction parameters to mimic bosonic symmetry protected topological phases with either gapless bosonic modes or spontaneous mirror symmetry breaking at the boundary; (3) For the spontaneous mirror symmetry breaking boundary, we also study various domain-wall defects between different mirror symmetry breaking order parameters at the boundary. Our results reveal that the thin film TMKI serves as an intriguing platform for the experimental studies of interacting topological phases.