Electronic structure of the Si-containing topological Dirac semimetal CaAl2Si2

Abstract

There has been an upsurge in the discovery of topological quantum materials, where various topological insulators and semimetals have been theoretically predicted and experimentally observed. However, only very few of them contains silicon, the most widely used element in electronic industry. Recently, ternary compound CaAl 2 Si 2 has been predicted to be a topological Dirac semimetal, hosting Lorentz-symmetry-violating quasiparticles with a strongly tilted conical band dispersion. In this work, by using high-resolution angle-resolved photoemission spectroscopy (ARPES), we investigated the comprehensive electronic structure of CaAl 2 Si 2 . A pair of topological Dirac crossings is observed along the k z direction, in good agreement with the ab initio calculations, confirming the topological Dirac semimetal nature of the compound. Our study expands the topological material family on Si-containing compounds, which have great application potential in realizing low-cost, nontoxic electronic device with topological quantum states.

Structural Metastability and Fermi Surface Topology of SrAl2Si2

“…Considering the metastable polymorphism of SrAl 2 Si 2 , it is no surprise that there are various emergent functionalities of this compound: the thermoelectricity, , superconductivity, distinct thermal character (Seebeck, thermal conductivity, , and specific heat), quantum linear magnetoresistivity (this work), and possibly topological Dirac semimetallicity. , …”

“…Considering the metastable polymorphism of SrAl 2 Si 2 , it is no surprise that there are various emergent functionalities of this compound: the thermoelectricity, 7,39 superconductivity, 9 distinct thermal character (Seebeck, thermal conductivity, 7,8 and specific heat 9 ), quantum linear magnetoresistivity (this work), and possibly topological Dirac semimetallicity. 40,41 It is worth mentioning that nonequilibrim transformation that traps a metastable phase (e.g., α β ⎯ → ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ ; eq 7a; afterward rapid quenching under clamped pressure) is a widely observed process. 3,38,42 Generally, such transformations lead to metastable structures as in, e.g., perovskite-related structures, 43 CaCO 3 , 44 intermetallic disilicides/digermindes AX 2 (A = Ca, Sr, Ba; X = Si, Ge), 45−50 rare-earth diantimonides RSb 2 (R = Dy−Lu, Y), 51 HfO 2 , 3 V 2 O 5 , 3 and AAl 2 Si 2 (A = Sr, Ba).…”

Structural metastability and Fermi surface Topology of SrAl2Si2

“…Considering the metastable polymorphism of SrAl 2 Si 2 , it is no surprise that there are various emergent functionalities of this compound: the thermoelectricity, 7,39 superconductivity, 9 distinct thermal character (Seebeck, thermal conductivity, 7,8 and specific heat 9 ), quantum linear magnetoresistivity (this work), and, possibly topological Dirac semimetallicity. 40,41 It is worth mentioning that nonequilibrim transformation that traps a metastable phase (e.g.…”

High Carrier Mobility in a Layered Antiferromagnet Integrated with Silicon

“…27 Recently, CaAl 2 Si 2 has been reported as a topological material with high-mobility carriers. 28,29 Therefore, we can choose Al as M and Si as X and expect high mobility in EuAl 2 Si 2 (Figure 1a), a magnetic analogue of CaAl 2 Si 2 carrier mobilities in Eu-based layered materials can be even higher than those in their alkaline earth counterparts. 4,14 What is particularly fortunate is that a route to produce epitaxial films of EuAl 2 Si 2 on silicon has been devised recently.…”

“…Making such a material is challenging not only because it requires specially developed synthetic routes but also because the carrier mobility in a nanomaterial is typically lower than that in the bulk . Recently, CaAl 2 Si 2 has been reported as a topological material with high-mobility carriers. , Therefore, we can choose Al as M and Si as X and expect high mobility in EuAl 2 Si 2 (Figure a), a magnetic analogue of CaAl 2 Si 2 carrier mobilities in Eu-based layered materials can be even higher than those in their alkaline earth counterparts. , What is particularly fortunate is that a route to produce epitaxial films of EuAl 2 Si 2 on silicon has been devised recently . Thus, this compound is an excellent candidate in a search for high carrier mobility in a magnetic layered nanomaterial.…”