Band splitting with vanishing spin polarizations in noncentrosymmetric crystals

Li, Kai; Luo, Wenhua; Ji, Junyi; Barone, Paolo; Picozzi, Silvia; Xiang, Hongjun

doi:10.1038/s41467-019-13197-z

Cited by 25 publications

(15 citation statements)

References 46 publications

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“…Interestingly, these bands are partially spinpolarized: it can be observed that the top valence bands are only spin-polarized in the vicinity of the K-point even though spin splitting occurs along the whole bandstructure path. This scenario was recently discussed by Liu and coworkers 35 who demonstrated that spin-orbit coupling can lead to spin splittings without spin polarization in non-magnetic materials without inversion symmetry.…”

Section: Heterobilayersmentioning

confidence: 84%

Flat band properties of twisted transition metal dichalcogenide homo- and heterobilayers of MoS$_2$, MoSe$_2$, WS$_2$ and WSe$_2$

Vitale¹,

Atalar²,

Mostofi³

et al. 2021

Preprint

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Twisted bilayers of two-dimensional materials, such as twisted bilayer graphene, often feature flat electronic bands that enable the observation of electron correlation effects. In this work, we study the electronic structure of twisted transition metal dichalcogenide (TMD) homo-and heterobilayers that are obtained by combining MoS2, WS2, MoSe2 and WSe2 monolayers, and show how flat band properties depend on the chemical composition of the bilayer as well as its twist angle. We determine the relaxed atomic structure of the twisted bilayers using classical force fields and calculate the electronic band structure using a tight-binding model parametrized from first-principles densityfunctional theory. For homobilayers, we find that the two highest valence bands exhibit a graphenelike dispersion and become flat as the twist angle is reduced. In contrast, not all heterobilayers have flat valence bands. Specifically, we find that those systems in which the highest valence band derives from K or K' states of the constituent monolayers do not exhibit flat bands, even at small twist angles. In all systems, qualitatively different band structures are obtained when atomic relaxations are neglected.

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Section: Heterobilayersmentioning

confidence: 84%

Flat band properties of twisted transition metal dichalcogenide homo- and heterobilayers of MoS$_2$, MoSe$_2$, WS$_2$ and WSe$_2$

Vitale¹,

Atalar²,

Mostofi³

et al. 2021

Preprint

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“…This contradiction implies that the pseudo--vector 𝑆 !" must vanish (even in spin split bands), as in two--dimensional SnTe thin film [45].…”

mentioning

confidence: 99%

Different shapes of spin textures as a journey through the Brillouin zone

et al. 2021

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Crystallographic space group symmetry (CPGS) such as polar and nonpolar crystal classes has long been known to classify compounds that have spin--orbit--induced spin splitting such as Rashba and Dresselhaus compounds, respectively. However, the enabling symmetries underlying the spin texture prototypes ---the relationship between the expectation value of spin operator 𝑆 !" in Bloch state 𝑢(𝑛, 𝑘) and the wavevector 𝑘 - are instead specific rotations and reflection symmetries in the wavevector point group symmetry rather than the presence or absence of polar field in the global crystallographic space group. Relativistic band structures calculations demonstrate how compounds judged by their macroscopic CPGS to be typical Dresselhaus (GaAs) or Rashba (GeTe) or Wyle (Tellurium) compounds, manifest both Rashba and Dresselhaus spin textures, respectively at different wavevector chiralities and polarities.

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“…Such quasipersistent spin textures [61] (promising for nondephasing spin transport [61,62]), together with large spin splitting, form another prospective aspect. Third, the discovery of different types of spin textures may promote exotic device applications as evidenced by, e.g., linear magnetoelectric effect driven by the "band splitting with vanishing spin polarizations" phenomenon [63]. We are also aware of interesting spin textures and mechanisms for Rashba spin splittings in multiferroic BiCoO 3 with canted spins [64].…”

Section: (B) (Ie With Soc) Using the Simple Expressionmentioning

confidence: 99%

Large spin splittings due to the orbital degree of freedom and spin textures in a ferroelectric nitride perovskite

et al. 2020

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First-principles simulations are conducted to predict that ferroelectric nitride perovskite LaWN 3 not only exhibits large spin splittings (2.7 eV Å) but also possesses unique spin textures for some of its conduction levels. Such spin splittings around the and L points cannot be interpreted as a typical mixture of Rashba or Dresselhaus configurations but rather require the development of four-band k • p models with high-order terms. We further identify that, for some bands, spin splittings can be greatly contributed by the pure orbital degree of freedom (PODF), a unique character of our four-band Hamiltonian compared to the traditional two-band version. The concept of PODF-enhanced spin splittings paves a way for designing materials with large spin splittings. Moreover, the energy levels possessing such large splittings and complex spin textures can be brought close to the conduction-band minimum by applying epitaxial strain.

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Band splitting with vanishing spin polarizations in noncentrosymmetric crystals

Cited by 25 publications

References 46 publications

Flat band properties of twisted transition metal dichalcogenide homo- and heterobilayers of MoS$_2$, MoSe$_2$, WS$_2$ and WSe$_2$

Flat band properties of twisted transition metal dichalcogenide homo- and heterobilayers of MoS$_2$, MoSe$_2$, WS$_2$ and WSe$_2$

Different shapes of spin textures as a journey through the Brillouin zone

Large spin splittings due to the orbital degree of freedom and spin textures in a ferroelectric nitride perovskite

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