Interplay of Dirac electrons and magnetism in CaMnBi2 and SrMnBi2

Abstract

Dirac materials exhibit intriguing low-energy carrier dynamics that offer a fertile ground for novel physics discovery. Of particular interest is the interplay of Dirac carriers with other quantum phenomena such as magnetism. Here we report on a two-magnon Raman scattering study of AMnBi2 (A=Ca, Sr), a prototypical magnetic Dirac system comprising alternating Dirac carrier and magnetic layers. We present the first accurate determination of the exchange energies in these compounds and, by comparison with the reference compound BaMn2Bi2, we show that the Dirac carrier layers in AMnBi2 significantly enhance the exchange coupling between the magnetic layers, which in turn drives a charge-gap opening along the Dirac locus. Our findings break new grounds in unveiling the fundamental physics of magnetic Dirac materials, which offer a novel platform for probing a distinct type of spin–Fermion interaction. The results also hold great promise for applications in magnetic Dirac devices.

Dirac fermions and possible weak antilocalization in LaCuSb2

“…It should be noted that this applies to a isotropic three-dimensional pocket and not a two-dimensional one, and thus LaCuSb2 appears to display more three-dimensional behavior than other 112 systems. The ultralow carrier mass obtained is found to be smaller than that for other 112 Dirac systems [16][17][18][19][20][21][22][23][24][25][26][27] , and is generally lower than one would expect for conventional (non-Dirac) carriers. These observations provide strong evidence for the presence of Dirac fermions in LaCuSb2.…”

“…The bandwidth of these linearly dispersing bands is determined by the Sb-Sb interatomic distance, which is 3.08Å in LaCuSb2. This distance is shorter than in some of the other aforementioned 112 Dirac materials, and thus results in linearly dispersive bands with relatively large bandwidths [16][17][18][19][20][21][22][23][24][25][26][27] . Using a path indicated by the primitive tetragonal Brillouin zone shown in Figure 1b, the calculated DFT band structures for LaCuSb2 excluding and including spin-orbit coupling (SOC) are shown in Figure 1c and Figure 1d, respectively.…”

Magneto-transport and electronic structures of BaZnBi2

“…The Mn-based ternary 112 type compounds (Ca/Sr/Ba/Eu/Yb)MnBi 2 [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] and (Ca/Sr/Ba/Yb)MnSb 2 [38][39][40][41][42] have been established as Dirac materials. In particular, YbMnBi 2 [36] and Sr 1−y Mn 1−z Sb 2 [38] have been further suggested as hosting time reversal symmetry (TRS) breaking Weyl fermions.…”

Pressure-Induced Large Volume Collapse, Plane-to-Chain, Insulator to Metal Transition in CaMn2Bi2

“…40 A common magnetic phenomenon associated with SOC is spin-canting, which has been observed and extensively investigated in various quantum systems such as SrMnBi2 and YbMnBi2. [48][49][50] Unfortunately, there is no direct evidence showing that spin-canting exists in CaMn2Bi2, suggesting that the interaction between SOC and magnetism is weak in this system at ambient pressure.…”