| 1. |
- Biswas, Deepnarayan, et al.
(författare)
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Ultrafast Triggering of Insulator-Metal Transition in Two-Dimensional VSe2
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:5, s. 1968-1975
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Tidskriftsartikel (refereegranskat)abstract
- The transition-metal dichalcogenide VSe2 exhibits an increased charge density wave transition temperature and an emerging insulating phase when thinned to a single layer. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these phases in single-layer VSe2 using ultrafast pump-probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap, which we disentangle from the ensuing hot carrier dynamics by fitting a model spectral function to the time-dependent photoemission intensity. This procedure leads to an estimated time scale of 480 fs for the closure of the gap, which suggests that the phase transition in single-layer VSe2 is driven by electron-lattice interactions rather than by Mott-like electronic effects. The ultrafast optical switching of these interactions in SL VSe2 demonstrates the potential for controlling phase transitions in 2D materials with light.
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| 2. |
- Corbae, Paul, et al.
(författare)
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Observation of spin-momentum locked surface states in amorphous Bi2Se3
- 2023
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 22:2, s. 200-206
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline symmetries have played a central role in the identification and understanding of quantum materials. Here we investigate whether an amorphous analogue of a well known three-dimensional strong topological insulator has topological properties in the solid state. We show that amorphous Bi2Se3 thin films host a number of two-dimensional surface conduction channels. Our angle-resolved photoemission spectroscopy data are consistent with a dispersive two-dimensional surface state that crosses the bulk gap. Spin-resolved photoemission spectroscopy shows this state has an anti-symmetric spin texture, confirming the existence of spin-momentum locked surface states. We discuss these experimental results in light of theoretical photoemission spectra obtained with an amorphous topological insulator tight-binding model, contrasting it with alternative explanations. The discovery of spin-momentum locked surface states in amorphous materials opens a new avenue to characterize amorphous matter, and triggers the search for an overlooked subset of quantum materials outside of current classification schemes.
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| 3. |
- de Vries, Petrus J, et al.
(författare)
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Natural clusters of tuberous sclerosis complex (TSC)-associated neuropsychiatric disorders (TAND) : new findings from the TOSCA TAND research project
- 2020
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Ingår i: Journal of Neurodevelopmental Disorders. - : Springer Science and Business Media LLC. - 1866-1955 .- 1866-1947. ; 12:1, s. 24-24
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Tuberous sclerosis complex (TSC)-associated neuropsychiatric disorders (TAND) have unique, individual patterns that pose significant challenges for diagnosis, psycho-education, and intervention planning. A recent study suggested that it may be feasible to use TAND Checklist data and data-driven methods to generate natural TAND clusters. However, the study had a small sample size and data from only two countries. Here, we investigated the replicability of identifying natural TAND clusters from a larger and more diverse sample from the TOSCA study.METHODS: As part of the TOSCA international TSC registry study, this embedded research project collected TAND Checklist data from individuals with TSC. Correlation coefficients were calculated for TAND variables to generate a correlation matrix. Hierarchical cluster and factor analysis methods were used for data reduction and identification of natural TAND clusters.RESULTS: A total of 85 individuals with TSC (female:male, 40:45) from 7 countries were enrolled. Cluster analysis grouped the TAND variables into 6 clusters: a scholastic cluster (reading, writing, spelling, mathematics, visuo-spatial difficulties, disorientation), a hyperactive/impulsive cluster (hyperactivity, impulsivity, self-injurious behavior), a mood/anxiety cluster (anxiety, depressed mood, sleep difficulties, shyness), a neuropsychological cluster (attention/concentration difficulties, memory, attention, dual/multi-tasking, executive skills deficits), a dysregulated behavior cluster (mood swings, aggressive outbursts, temper tantrums), and an autism spectrum disorder (ASD)-like cluster (delayed language, poor eye contact, repetitive behaviors, unusual use of language, inflexibility, difficulties associated with eating). The natural clusters mapped reasonably well onto the six-factor solution generated. Comparison between cluster and factor solutions from this study and the earlier feasibility study showed significant similarity, particularly in cluster solutions.CONCLUSIONS: Results from this TOSCA research project in an independent international data set showed that the combination of cluster analysis and factor analysis may be able to identify clinically meaningful natural TAND clusters. Findings were remarkably similar to those identified in the earlier feasibility study, supporting the potential robustness of these natural TAND clusters. Further steps should include examination of larger samples, investigation of internal consistency, and evaluation of the robustness of the proposed natural clusters.
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| 4. |
- Horio, M., et al.
(författare)
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Orbital-selective metal skin induced by alkali-metal-dosing Mott-insulating Ca 2 RuO 4
- 2023
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Ingår i: Communications Physics. - 2399-3650. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.
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| 5. |
- Jacob, Mina A, et al.
(författare)
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Global Differences in Risk Factors, Etiology, and Outcome of Ischemic Stroke in Young Adults: A Worldwide Meta-analysis: The GOAL-Initiative.
- 2022
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Ingår i: Neurology. - 1526-632X. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- There is a worldwide increase in the incidence of stroke in young adults, with major regional and ethnic differences. Advancing knowledge of ethnic and regional variation in causes and outcomes will be beneficial in implementation of regional healthcare services. To study the global distribution of risk factors, causes and 3-month mortality of young ischemic stroke patients, by performing a patient data meta-analysis form different cohorts worldwide.We did a pooled analysis of individual patient data from cohort studies which included consecutive ischemic stroke patients aged 18-50 years. We studied differences in prevalence of risk factors and causes between different ethnic and racial groups, geographic regions and countries with different income levels. We investigated differences in 3-month mortality by mixed-effects multivariable logistic regression.We included 17,663 patients from 32 cohorts in 29 countries. Hypertension and diabetes were most prevalent in Blacks (hypertension, 52.1%; diabetes, 20.7%) and Asians (hypertension 46.1%, diabetes, 20.9%). Large vessel atherosclerosis and small vessel disease were more often cause of stroke in high-income countries (HICs; both p<0.001), whereas ''other determined stroke'' and ''undetermined stroke'' were higher in low and middle-income countries (LMICs; both p<0.001). Patients in LMICs were younger, had less vascular risk factors, and despite this, more often died within 3 months than those from HICs (OR 2.49; 95% CI 1.42-4.36).The ethnoracial and regional differences in risk factors and causes of stroke at young age provide an understanding of ethnic and racial, and regional differences in incidence of ischemic stroke. Our results also visualize the dissimilarities in outcome after stroke in young adults that exist between LMICs and HICs, which should serve as call to action to improve healthcare facilities in LMICs.
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| 6. |
- Jones, Alfred J. H., et al.
(författare)
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Visualizing band structure hybridization and superlattice effects in twisted MoS2/WS2 heterobilayers
- 2022
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Ingår i: Current Opinion in Chemical Engineering. - : IOP Publishing Ltd. - 2211-3398. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- A mismatch of atomic registries between single-layer transition metal dichalcogenides (TMDs) in a two-dimensional (2D) van der Waals heterostructure produces a moire superlattice with a periodic potential, which can be fine-tuned by introducing a twist angle between the materials. This approach is promising both for controlling the interactions between the TMDs and for engineering their electronic band structures, yet direct observation of the changes to the electronic structure introduced with varying twist angle has so far been missing. Here, we probe heterobilayers comprised of single-layer MoS2 and WS2 with twist angles ranging from 2 degrees to 20 degrees and determine the twist angle-dependent evolution of the electronic band structure using micro-focused angle-resolved photoemission spectroscopy. We find strong interlayer hybridization between MoS2 and WS2 electronic states at the (Gamma) over bar -point of the Brillouin zone, leading to a shift of the valence band maximum in the heterostructure. Replicas of the hybridized states are observed at the center of twist angle-dependent moire mini Brillouin zones. We confirm that these replica features arise from the inherent moire potential by comparing our experimental observations with density functional theory calculations of the superlattice dispersion. Our direct visualization of these features underscores the potential of using twisted heterobilayer semiconductors to engineer hybrid electronic states and superlattices that alter the electronic and optical properties of 2D heterostructures for a wide range of twist angles.
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| 7. |
- Abbafati, Cristiana, et al.
(författare)
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- 2020
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Tidskriftsartikel (refereegranskat)
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