Giant magnetoresistance in layered manganese pnictide CaMnBi2

Low-energy electronic structures in AMnBi 2 (A=alkaline earths) are investigated using a first-principles calculation and a tight binding method. An anisotropic Dirac dispersion is induced by the checkerboard arrangement of A atoms above and below the Bi square net in AMnBi 2 . SrMnBi 2 and CaMnBi 2 have a different kind of Dirac dispersion due to the different stacking of nearby A layers, where each Sr (Ca) of one side appears at the coincident (staggered) xy position of the same element at the other side. Using the tight binding analysis, we reveal the chirality of the anisotropic Dirac electrons as well as the sizable spin-orbit coupling effect in the Bi square net. We suggest that the Bi square net provides a platform for the interplay between anisotropic Dirac electrons and the neighboring environment such as magnetism and structural changes.

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“…[12][13][14][15][16]22 In Fig. 3, we show the energy dispersion near the Dirac point at k 0 without including the SOC.…”

Section: Dft Resultsmentioning

confidence: 99%

“…15,16 This indicates that the low-energy electron motion in the Bi square net can be described by the Dirac Hamiltonian. So far, however, the origin of the Dirac fermions in the Bi square net has not yet been investigated clearly.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Dirac electronic structures ofAMnBi2(A=Sr,Ca)

et al. 2013

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“…Interestingly, the Dirac cones are highly anisotropic in the xy plane, due to weak hybridization with A site d xy,yz orbitals. A substantial amount of experimental evidence for anisotropic Dirac fermions in the Bi layer exists from measurements of magnetization, magnetotransport, angle-resolved photoemission spectra (ARPES) and magnetothermopower 3,4,8,[10][11][12][13] . Other bands predicted by DFT are also seen in ARPES.…”

Section: Introductionmentioning

confidence: 99%

Coupling of magnetic order to planar Bi electrons in the anisotropic Dirac metalsAMnBi2 (A =Sr,Ca)

et al. 2014

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We report powder and single crystal neutron diffraction measurements of the magnetic order in AMnBi2 (A = Sr and Ca), two layered manganese pnictides with anisotropic Dirac fermions on a Bi square net. Both materials are found to order at TN ≈ 300 K in k = 0 antiferromagnetic structures, with ordered Mn moments at T = 10 K of approximately 3.8 µB aligned along the c axis. The magnetic structures are Néel-type within the Mn-Bi layers but the inter-layer ordering is different, being antiferromagnetic in SrMnBi2 and ferromagnetic in CaMnBi2. This allows a meanfield coupling of the magnetic order to Bi electrons in CaMnBi2 but not in SrMnBi2. We find clear evidence that magnetic order influences electrical transport. First principles calculations explain the experimental observations and suggest that the mechanism for different inter-layer ordering in the two compounds is the competition between the anteiferromagnetic superexchange and ferromagnetic double exchange carried by itinerant Bi electrons.

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“…By means of time-resolved ARPES (TARPES), we study the ultrafastly-induced dynamics in SrMnBi 2 , which is a new type of Dirac materials that has layers of quasi-two-dimensional Dirac fermions [34][35][36][37][38]. Utilizing the high energy resolution and stability of our apparatus [39], we investigated the carrier dynamics induced by various pump-power values (P 's).…”

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confidence: 99%

Revealing the ultrafast light-to-matter energy conversion before heat diffusion in a layered Dirac semimetal

et al. 2016

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There is still no general consensus on how one can describe the out-of-equilibrium phenomena in matter induced by an ultrashort light pulse. We investigate the pulse-induced dynamics in a layered Dirac semimetal SrMnBi2 by pump-and-probe photoemission spectroscopy. At 1 ps, the electronic recovery slowed upon increasing the pump power. Such a bottleneck-type slowing is expected in a two-temperature model (TTM) scheme, although opposite trends have been observed to date in graphite and in cuprates. Subsequently, an unconventional power-law cooling took place at ∼100 ps, indicating that spatial heat diffusion is still ill defined at ∼100 ps. We identify that the successive dynamics before the emergence of heat diffusion is a canonical realization of a TTM scheme. Criteria for the applicability of the scheme is also provided.

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Giant magnetoresistance in layered manganese pnictide CaMnBi2

Cited by 63 publications

References 21 publications

Anisotropic Dirac electronic structures ofAMnBi2(A=Sr,Ca)

Anisotropic Dirac electronic structures ofAMnBi2(A=Sr,Ca)

Coupling of magnetic order to planar Bi electrons in the anisotropic Dirac metalsAMnBi2 (A =Sr,Ca)

Revealing the ultrafast light-to-matter energy conversion before heat diffusion in a layered Dirac semimetal

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