Anomalous Z2 antiferromagnetic topological phase in pressurized SmB6

Abstract

Antiferromagnetic materials, whose time-reversal symmetry is broken, can be classified into the Z2 topology if they respect some specific symmetry. Since the theoretical proposal, however, no materials have been found to host the antiferromagnetic topological (AFT) phase to date. Here, for the first time, we demonstrate that the topological Kondo insulator SmB6 can be an AFT system when pressurized to undergo an antiferromagnetic phase transition. In addition to propose the possible candidate for an AFT material, in this work we also illustrate the anomalous topological surface states of the AFT phase which has not been discussed before. Originating from the interplay between the topological properties and the antiferromagnetic surface magnetization, the topological surface states of the AFT phase behave differently as compared with those of a topological insulator. Besides, the AFT insulators are also found promising in the generation of tunable spin currents, which is an important application in spintronics.

Reflection-Symmetry Protected Antiferromagnetic Topological Insulator in Three-Dimensional Heavy-Fermion Systems

“…The non-magnetic topological Kondo insulator SmB 6 at ambient pressure turns into a metallic AF phase by high pressure above 6GPa, although its magnetic ordering pattern is not clarified experimentally. In a previous theoretical study [29], it is pointed out that the ground state is the A-AF phase with m ẑ and the Z 2 -AFTI phase emerges in this AF phase. In this paper, motivated by recent experimental studies in pressurized SmB 6 , we consider the topological properties of the AF phase from the viewpoint of reflection symmetry.…”

“…The topological properties of the AF phase have attracted much attention from the viewpoint of theoretical and experimental investigation. From the first-principle calculation, it is pointed out that the pressurized SmB 6 would serve as a better candidate for a Z 2 -AFTI and the A-type AF (A-AF) configuration is proposed for its ground state [29].…”

“…To be specific, we here consider it in the 3D heavy-fermion systems and demonstrate how the paramagnetic (PM) phase changes into the AF phase by using the Hartree-Fock (HF) approximation. We focus on the A-AF phase of SmB 6 which is proposed by the first-principle study [29]. In the previous study, we proposed a reflection-symmetric AFTI phase in 2D [30], which can have a topologically nontrivial structure specified by a mirror Chern number.…”

Unusual change in the Dirac-cone energy band upon a two-step magnetic transition in CeBi

“…Taking into account such magnetic and topological aspects of RX p family, one would naturally expect that CeBi is a unique candidate to study the interplay between magnetism and topological properties, since it shows interesting magnetic phases characterized by a two-step antiferromagnetic (AF) transition at T = 25 and 14 K under zero-magnetic field [3,4], in addition to the expected topological nature. In a broader perspective, it is of great importance to experimentally clarify the role of antiferromagnetism to the topological properties, which is currently a target of intensive debates in theories [49][50][51][52][53][54][55][56][57][58][59][60][61] while no concrete experimental data have been hitherto reported.…”

Signature of topological states in antiferromagnetic Sm-substituted Bi2Te3

“…Here it is noteworthy that the rare-earth elements of Ce and Gd are expected to tune only the magnetism, not affect the electrical transport because they are mostly isovalent to the Bi atom and comparable in size. In theoretical aspect, some candidates such as GdBiPt and pressurized SmB 6 have been proposed as antiferromagnetic TIs 18,25,26 . Very recently, MnBi 2 Te 4…”