Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi

Abstract

LaBi is a three-dimensional rock-salt-type material with a surprisingly quasi-two-dimensional electronic structure. It The search of an extra degree of freedom has played a significant role in modern technological advancements. In spintronics, one adds the spin degree of freedom in charge devices [1,2], whereas in the magnetoelectric multiferroics, the polarization can be manipulated by a magnetic field and vice versa [3,4]. In recent years, a new field named valleytronics shows great promise particularly in materials with two-dimensional (2D) electronic structures based on their layered crystal structure. For example in graphene, linearly dispersing conical bands (valleys) touch at the high symmetry points of the Brillouin zone (BZ) and one of the exciting aspects for exploiting such a band structure is to occupy (polarize) one valley much larger than another in a controlled fashion. This enables graphene to be used for valley valves and valley filters [5,6]. In contrast to graphene, monolayers of some of the transition metal dichalcogenides (TMDs) inherit broken inversion symmetry with finite band gap. The absence of inversion symmetry and a finite band gap provide crucial electrical and optical control of the valley degree of freedom. [7][8][9]

Separation of electron and hole dynamics in the semimetal LaSb

“…with that reported in other XMR materials [12,50]. Such a quadratic relationship that implies a non-saturating magnetoresistance can be derived from the isotropic two-band model with e-h compensation [12], which has become the most prevalent explanation for the origin of the XMR [12,27,34,36,37]. Indeed, ARPES experiments [42] Furthermore, the isotropic two-band mode cannot account for the four-fold angle dependence of the resistivity ρ(θ), as delineated in Fig.4(b).…”

“…We demonstrate that investigation on anisotropic magnetoresistance can provide a convenient way to separate the dynamics of the charge carriers and to uncover the origin of XMR in multi-band materials with anisotropic Fermi surfaces. This revealed mechanism can account for the XMR observed in other semimetals [9][10][11][12][13][14][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49].…”

“…We show that the Fermi surfaces derived from our Shubnikov -de Haas (SdH) quantum oscillation measurements are in fact bulk Fermi pockets instead of surface ones. Furthermore, these materials have ellipsoidal electron Fermi pockets elongated along the Γ-X direction [27,35,36], which can result in an angle-dependent magnetoresistance [36,37,[44][45] due to the anisotropic effective mass that governs the mobility of the charge carriers. Hence, a quantitative analysis of the angle dependence of the magnetoresistance may enable to reveal the role of each band / Fermi pocket on the XMR.…”

“…Other mechanisms such as a magnetic-field induced metal-insulator transition (MIT) [28][29][30][31][32][33], electron-hole (e-h) compensation [12,18,27,34], and forbidden backscattering at zero field [15] have also been considered as possible origins for XMR. Recently, the rare-earth monopnictides LnX (Ln = La/Y/Nd/Ce and X = Sb/Bi) [27,[34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] were added to the family of XMR materials. These materials, with a rock-salt cubic crystal lattice, exhibit typical hallmark XMR behavior such as power-law magnetoresistance and magnetic-field induced turn-on behavior as a function of temperature.…”

Angular Dependence of Interlayer Magnetoresistance for Antiferromagnetic Dirac Semimetal AMnBi2 (A = Sr, Eu)

“…This leads to a four-fold angular dependence of interlayer MR, which is reproduced by considering the semi-classical transport theory on the anisotropic Fermi surface [4]. The magnitude of resistive anisotropy is enhanced at high fields, indicating the valley-polarized conduction controlled by the in-plane field [5][6][7]. There, the influence of the Mn spins appears to be negligible, because the antiferromagnetic order of the Mn spins has a high transition temperature (∼295 K) and hence it will be hardly modulated by the in-plane field of a few tesla at low temperatures.…”