| 1. |
- Bahramy, M. S., et al.
(författare)
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Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides
- 2018
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Ingår i: Nature Materials. - 1476-1122. ; 17:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied bulk properties, while their single-layer variants have become one of the most prominent examples of two-dimensional materials beyond graphene. Their disparate ground states largely depend on transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date. Here, we focus on the chalcogen-derived states. From density-functional theory calculations together with spin- and angle-resolved photoemission, we find that these generically host a co-existence of type-I and type-II three-dimensional bulk Dirac fermions as well as ladders of topological surface states and surface resonances. We demonstrate how these naturally arise within a single p-orbital manifold as a general consequence of a trigonal crystal field, and as such can be expected across a large number of compounds. Already, we demonstrate their existence in six separate TMDs, opening routes to tune, and ultimately exploit, their topological physics.
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| 2. |
- Haider, Jutta, et al.
(författare)
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Pairing information with poverty : Traces of development discourse in LIS
- 2006
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Ingår i: New Library World. ; 107:9-10, s. 371-385
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - The purpose of this research is to investigate and critically assess the notions of "information poverty" in LIS by highlighting its connections with development discourse.Design/methodology/approach - The article takes a discourse analysis approach, which starts from Michel Foucault's understanding of discourse. "Information poverty" is posited as a statement and investigated in its relation to other statements. The focus is on discursive procedures that emerge from the repeated connections between statements. The article draws on the interpretative analysis of 35 English language articles published in scholarly and professional LIS journals between 1995 and 2005.Findings - "Information poverty" and the "information poor" are established as being assigned specific positions in the discourse of LIS as the result of overlapping, sometimes conflicting discursive procedures. The concept emerges as a possibility in LIS by anchoring it in the dominant discourse of development. Traces of development discourse surface in LIS and contribute to the legitimisation of the concept of "information poverty" by lending it authority.Research limitations/implications - The material selection is linguistically biased. Results and findings are fully applicable only in an English language context.Originality/value - The article relates the professional discourse of LIS to the dominant discourse of development and thus highlights some of the assumptions upon which the concept of "information poverty" is built. Moreover, the article is intended to contribute to the further development of discourse analysis in LIS.
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| 3. |
- Riley, J. M., et al.
(författare)
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Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor
- 2014
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Ingår i: Nature Physics. - 1745-2473. ; 10:11, s. 835-839
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Tidskriftsartikel (refereegranskat)abstract
- Methods to generate spin-polarized electronic states in nonmagnetic solids are strongly desired to enable all-electrical manipulation of electron spins for new quantum devices(1). This is generally accepted to require breaking global structural inversion symmetry(1-5). In contrast, here we report the observation from spin- and angle-resolved photoemission spectroscopy of spin-polarized bulk states in the centrosymmetric transition-metal dichalcogenide WSe2. Mediated by a lack of inversion symmetry in constituent structural units of the bulk crystal where the electronic states are localized(6), we show how spin splittings up to similar to 0.5 eV result, with a spin texture that is strongly modulated in both real and momentum space. Through this, our study provides direct experimental evidence for a putative locking of the spin with the layer and valley pseudospins in transition-metal dichalcogenides(7,8), of key importance for using these compounds in proposed valleytronic devices.
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| 4. |
- Thiagarajan, Balasubramanian, et al.
(författare)
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Spin-valley locking in the normal state of a transition-metal dichacogenide superconductor
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Metallic transition-metal dichalcogenides (TMDCs) are benchmark systems for studying and controlling intertwined electronic orders in solids, with superconductivity developing from a charge-density wave state. The interplay between such phases is thought to play a critical role in the unconventional superconductivity of cuprates, Fe-based and heavy-fermion systems, yet even for the more moderately-correlated TMDCs, their nature and origins have proved controversial. Here, we study a prototypical example, 2H-NbSe2, by spin- and angle-resolved photoemission and first-principles theory. We find that the normal state, from which its hallmark collective phases emerge, is characterized by quasiparticles whose spin is locked to their valley pseudospin. This results from a combination of strong spin–orbit interactions and local inversion symmetry breaking, while interlayer coupling further drives a rich three-dimensional momentum dependence of the underlying Fermi-surface spin texture. These findings necessitate a re-investigation of the nature of charge order and superconducting pairing in NbSe2 and related TMDCs.
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