Experimental Determination of the Topological Phase Diagram in Cerium Monopnictides

Abstract

Experimental determinations of bulk band topology in the solid states have been so far restricted to only indirect investigation through the probing of surface states predicted by electronic structure calculations. We here present an alternative approach to determine the band topology by means of bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy. We investigate the bulk electronic structures of the series materials, Ce monopnictides (CeP, CeAs, CeSb, and CeBi). By performing a paradigmatic study of the band structures as a function of their spin-orbit coupling, we draw the topological phase diagram and unambiguously reveal the topological phase transition from a trivial to a nontrivial regime in going from CeP to CeBi induced by the band inversion. The underlying mechanism of the phase transition is elucidated in terms of spin-orbit coupling in concert with their semimetallic band structures. Our comprehensive observations provide a new insight into the band topology hidden in the bulk states.

Multiple metamagnetism, extreme magnetoresistance and nontrivial topological electronic structures in the magnetic semimetal candidate holmium monobismuthide

“…Nontrivial Berry phase obtained in the ferromagnetic state of HoSb indirectly reveals its topological nature as well [36]. Bulksensitive soft x-ray ARPES confirms that CeBi is topologically nontrivial by observation of its band inversion [37]. Besides, ferromagnetic GdSb is speculated to be a Weyl semimetal candidate, which still needs further experimental confirmation [38].…”

Large Fermi surface expansion through anisotropic mixing of conduction and f electrons in the semimetallic Kondo lattice CeBi

“…The low carrier density significantly reduces the Kondo screening, while the small FS allows for easy detection of any change in the Fermi wavevector kF due to valence fluctuations. Low carrier density Kondo systems have attracted considerable interest recently, in view of novel phenomena such as unconventional quantum criticality and correlated topological states [10,11,12,13,14].…”

Magnetization-governed magnetoresistance anisotropy in the topological semimetal CeBi

“…extensively sought, leading to the recent revelation of magnetic topological insulator MnBi2Te4 [13][14][15][16][17][18][19][20]. Since 2016, researchers have also been searching for other types of topological materials with intrinsic magnetic order and uncovered a number of magnetic topological semimetals [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], which may lead to topologically-driven spintronics [37] and have become a focus center in the field . Extensive exploration of these materials has led to the discovery of exotic properties.…”

“…Magnetization measurements revealed rich magnetic phases including antiferromagnetic, ferrimagnetic and ferromagnetic phases, depending on temperature and magnitude of the magnetic field [41,45]. In the context of topological materials, CeBi recently has attracted renewed interest as it has been identified to be a topological semimetal in angleresolved photoemission spectroscopy (ARPES) experiments [38,47]. It is also the only known magnetic topological semimetal that shows extremely large magnetoresistance (XMR) [47].…”

“…CeBi has a rock-salt cubic crystal lattice, resulting in identical electronic structures along the kx, ky and kz directions of the Brillouin zone [47]. Similar to its non-magnetic rare-earth monopnictide counterpart LaSb [49], CeBi has a bulk anisotropic Fermi surface with elongated electron Fermi pockets [38,47]. Thus, we expect to see anisotropic MR in CeBi in a rotating magnetic field.…”