Strain-tunable triple point Fermions in diamagnetic rare-earth half-Heusler alloys

Abstract

Topologically non-trivial electronic structure is a feature of many rare-earth half-Heusler alloys, which host atoms with high spin-orbit coupling bringing in the non-triviality. In this article, using the first-principles simulations, rare-earth half-Heusler YPdBi, ScPdBi, LaPdBi, LuPdBi, YPtBi and LuPtBi alloys are studied under strain to reveal multiple band inversions associated with topological phase transitions. From our simulations we find that, as a result of first band-inversion, the Brillouin zone of the diamagnetic half-Heusler alloys hosts eight triple points whereas, the second band inversion causes the emergence of sixteen more triple points. These band-inversions are observed to be independent of the spin-orbit coupling and are the reason behind increasing occupation of bismuth 7s orbitals as volume of the unit cell increases. The surface electronic transport in different triple point semi-metallic phases is found to evolve under strain, as the number of Fermi arcs change due to multiple band inversions. Once the second band inversion occurs, further application of tensile strain does not increase the number of triple points and Fermi arcs. However, increasing tensile strain (or decreasing compressive strain) pushes the triple point crossing to higher momenta, making them more effective as source of highly mobile electrons. These observations make a pathway to tune the bulk as well as surface transport through these semi-metals by application of tensile or compressive strain depending on the unstrained relative band-inversion strength of the material.

Calculation of Structural, Electronic, Optical, and Thermoelectric Properties of XPdBi (X = La, Sc, Y): Materials for Optoelectronic Devices

“…The calculated lattice constants and the bulk moduli of the XPdBi (X = La, Sc, Y) semiconductors are in good agreement with the experimental and theoretical results [5,8,16,[19][20][21][22][23][24][25]. The calculated lattice constants of XYZ systems differ only slightly from their experimental analogs [16,[21][22][23][24].…”

“…The total energy was calculated by varying the volume to determine the equilibrium lattice parameter and bulk modulus, and the curves were fitted by the Murnaghan equation of state [15]. The structural parameters results (lattice constants (a) and bulk modulus (B), its pressure derivative (B ), and minimum energy at equilibrium E 0 ) are listed in Table I [5,8,[16][17][18][19][20][21][22][23][24][25][26][27]. The calculated lattice constants and the bulk moduli of the XPdBi (X = La, Sc, Y) semiconductors are in good agreement with the experimental and theoretical results [5,8,16,[19][20][21][22][23][24][25].…”

“…The structural parameters results (lattice constants (a) and bulk modulus (B), its pressure derivative (B ), and minimum energy at equilibrium E 0 ) are listed in Table I [5,8,[16][17][18][19][20][21][22][23][24][25][26][27]. The calculated lattice constants and the bulk moduli of the XPdBi (X = La, Sc, Y) semiconductors are in good agreement with the experimental and theoretical results [5,8,16,[19][20][21][22][23][24][25]. The calculated lattice constants of XYZ systems differ only slightly from their experimental analogs [16,[21][22][23][24].…”

Computational Simulation of the Electronic State Transition in the Ternary Hexagonal Compound BaAgBi

“…Topological states in metals can be classified into different types based on different band crossing conditions and intertwining shapes. For example, nodal point ( Zhang et al, 2017a ; Cano et al, 2019 ; He et al, 2019 ; Li et al, 2020 ; Li and Xia, 2020 ), nodal line ( Chang et al, 2016a ; Hosen et al, 2018 ; Kim et al, 2018 ; Takane et al, 2018 ; Zheng et al, 2019 ; Wang et al, 2020a ; Wang et al, 2020b ; He et al, 2020 ; Jin et al, 2020 ; Wang et al, 2021a ; He et al, 2021 ; Zhou et al, 2021 ), and nodal surface ( Fu et al, 2019 ; Yang et al, 2019 ; Yang et al, 2020 ; Yang and Zhang, 2020 ) can be differentiated by their band crossing dimensionality: Weyl ( Huang et al, 2015 ; Soluyanov et al, 2015 ; Chang et al, 2016b ; Jia et al, 2016 ; Wang et al, 2018a ), triple ( Jin et al, 2019a ; Bhattacharya et al, 2021 ), Dirac ( Galanakis and Mavropoulos, 2007 ; Heikkilä and Volovik, 2011 ; He et al, 2016 ; Zhang et al, 2017b ; Zhang et al, 2018a ; Wang et al, 2018b ; Wang et al, 2019 ), sextuple, and octuple topological states ( Bradlyn et al, 2016 ), which can also be distinguished by their band crossing degeneracy. Some other classifications can also be defined based on their band dispersion rates or band crossing shapes ( Bzdušek et al, 2016 ; Chen et al, 2017 ; Wang et al, 2017 ; Zhang et al, 2018b ).…”