Higher-order topological insulators in a crisscross antiferromagnetic model

Abstract

We present a 4 ′ /m ′ -respecting crisscross AFM model in 2D and 3D, both belonging to the Z2 classification and exhibiting interesting magnetic high-order topological insulating (HOTI) phases. The topologically nontrivial phase in the 2D model is characterized by the fractional charge localized around the corners and the quantized charge quadrupole moment. Moreover, our 2D model also exhibits the quantized magnetic quadrupole moment, which is a unique feature compared with previous studies. The 3D system stacked from layers of the 2D model possesses the HOTI phase holding chiral 1D metallic states on the hinge, which corresponds to the Wannier center flow between the valence and conduction bands. The novel transport properties such as the half-quantum spin-flop pumping phenomena on the side surfaces of the HOTI phase is also discussed.

Fragile topologically flat band in the checkerboard antiferromagnetic monolayer FeSe

“…In Fig. 4d, we plot the spatial distribution of the two occupied corner states, which are localized at four corners and each corner has e/2 charge, corresponding to previous conclusions of the HOTI protected by C 4z T symmetry very well [15]. Finally, we emphasize that such calculated corner states are strongly supported by the previous experimental observations, in which bound state near the Fermi level has been observed at the crossing point of four domain walls by scanning tunneling microscopy [45].…”

“…Such filling anomaly could give rise to partially occupied corner states at the sample corner of a 2D HOTI [12,14]. In the system with S 4z symmetry, one can identify a HOTI by the S 4z eigenvalues of occupied bands [11,15]. We develop a Fu-Kane-like formula to compute the HOTI indicator Z as following, FM boundary (cut #2 and cut #3 in Fig.…”

“…Introduction -Topological matters have attracted extensive interest for their novel and robust bulk-boundary correspondence [1][2][3][4][5]. In particular, the interplay between the crystal symmetry and electronic bands gives rise to a variety of topological states, such as the topological crystalline insulator [6][7][8] and higher-order topological insulator (HOTI) [9][10][11][12][13][14][15]. Moreover, when the magnetism and topological bands are entangled together, it will greatly enrich more exotic topological states [16][17][18][19][20][21][22], such as the quantum anomalous Hall effect [18,23], axion topological insulators [24,25], and magnetic topological semimetals [26,27].…”

Fragile topological band in the checkerboard antiferromagnetic monolayer FeSe

“…Topological matters have attracted extensive interest for their distinct and robust bulk-boundary correspondence [1][2][3][4][5] . In particular, the interplay between the crystal symmetry and electronic bands gives rise to a variety of topological states, such as the topological crystalline insulator [6][7][8][9] and higher-order topological insulator (TI) [10][11][12][13][14][15][16] . Moreover, when the magnetism and topological bands are entangled together, it will greatly enrich more exotic topological states [17][18][19][20][21][22][23] , such as the quantum anomalous Hall effect 20,21 , axion TIs 24,25 , and magnetic topological semimetals 26,27 .…”

Higher-Order Topology in Monolayer FeSe

“…Currently, although a variety of theoretical models are proposed for the 2D SOTI [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], its material realization is still a challenging task. Besides some artificial macro-structures [30][31][32][33][34][35][36], few realistic electronic materials have been reported.…”