Distinct topological properties in Ce monopnictides having correlated f electrons: CeN vs. CeBi

Abstract

The hitherto-studied topological nature in Ce monopnictides (CePn) has been discussed based solely on their p-d band inversion, despite the existence of f electrons. Interestingly, however, we have found that CeN, the lightest CePn, has nontrivial Z 2 topology originating from f-d band inversion. Through density-functional theory and dynamical mean-field theory calculations, we have demonstrated that, among the correlated felectron systems of CePn, the lightest CeN is a coherent narrow f-band system having an f-d band-inverted topological Kondo insulator nature, whereas the heaviest CeBi is a strongly localized f-electron system having a conventional p-d band-inverted topological insulator nature. For CeN, topological surface states (TSSs) are identified clearly on three different (001), (110), and (111) surfaces. For CeBi, however, TSSs are identified only on the (111) surface. Furthermore, intriguing topological-crystalline insulator-type TSSs are identified on the (110) surfaces of both CeN and CeBi.

Prediction of spin polarized Fermi arcs in quasiparticle interference in CeBi

“…It is worth mentioning that the DFT + U method for a nonmagnetic phase will still leave the f electron pinned around the Fermi level, which is completely different from the spin-polarized case [44]. Therefore, the DFT + U approach is not appropriate to describe strongly correlated materials in a paramagnetic state, for which one needs to resort to more powerful methods like DFT + DMFT [45].…”

Band theoretical approaches to topological physics in strongly-correlated f-electron Kondo systems

“…Then the coherent f-band in CeN is expected to produce f -d band inversion, which leads to a nontrivial Z 2 topology of TKI nature. It has been recently reported that TSSs are actually identified on three different (001), (110), and (111) surfaces [25].…”

“…Strongly-correlated ( f ) TI Bi 1−x Sb x [9], Bi 2 Se 3 [10,11] S m B 6 [22], CeOs 4 As 12 [23], SmO [24], CeN [25], AmN [26], PuB 6 [27] TCI SnTe [12] S m B 6 [28], YbB 12 [29] Dirac/Weyl Na 3 Bi [13], Cd 3 As 2 [14], TaAs [15] C e 3 Bi 4 Pd 3 [30], CeRu 4 Sn 6 [31], CeAlGe [32], EuB 6 [33], UNiSn The key ingredient that makes the difference has something to do with the degree of the renormalization factor (quasi-particle weight) Z F , arising from the Coulomb correlation interaction of 4 f electrons. The renormalization factor Z F can be obtained from the slope of the real-part of the selfenergy Σ(ω) at E F .…”

“…Nevertheless, quite a few reports on the topological properties of f-electron systems are now available, revealing that the Kondo physics in f-electron systems can play an important role in realizing the non-trivial topology. As listed in table 1, since the first proposal of topological Kondo insulator candidate SmB 6 [22], several candidates of real topological materials have been predicted for topological Kondo insulators (TKIs) [23][24][25], topological-crystalline Kondo insulators (TCKIs) [28,29], Weyl/Dirac semimetals [30][31][32][33]45], and so on. Combining the TKI nature with nonsymmorphic symmetry, the emergence of Möbius-twisted surface states of hourglass-type were also predicted on a specific surface of CeNiSn [37].…”

Unconventional surface state pairs in a high-symmetry lattice with anti-ferromagnetic band-folding

“…The nonmagnetic LaPn were first predicted as topologically non-trivial due to the band inversion between La d and Pn p orbitals 2 . The crossover and trend of such d-p band inversion in the RPn series have been studied by experiments [3][4][5][6][7][8] and calculations 9,10 , which have largely focused on the paramagnetic state. The gradual filling of the 4 f orbitals and change of spin-orbit coupling (SOC) strength across the RPn series can potentially bring high tunability in the multitude of topological states when coupled with magnetic properties [11][12][13][14][15][16] .…”