Valley-hybridized gate-tunable 1D exciton confinement in MoSe2

Controlling excitons at the nanoscale in semiconductor materials represents a formidable challenge in the fields of quantum photonics and optoelectronics. Achieving this control holds great potential for unlocking strong exciton-exciton interaction regimes, enabling exciton-based logic operations, exploring exotic quantum phases of matter, facilitating deterministic positioning and tuning of quantum emitters, and designing advanced optoelectronic devices. Monolayers of transition metal dichalcogenides (TMDs) offer inherent two-dimensional confinement and possess significant binding energies, making them particularly promising candidates for achieving electric-field-based confinement of excitons without dissociation. While previous exciton engineering strategies have predominantly focused on local strain gradients, the recent emergence of electrically confined states in TMDs has paved the way for novel approaches. Exploiting the valley degree of freedom associated with these confined states further broadens the prospects for exciton engineering. Here, we show electric control of light polarization emitted from one-dimensional (1D) quantum confined states in MoSe2. By employing non-uniform in-plane electric fields, we demonstrate the in-situ tuning of the trapping potential and reveal how gate-tunable valley-hybridization gives rise to linearly polarized emission from these localized states. Remarkably, the polarization of the localized states can be entirely engineered through either the spatial geometry of the 1D confinement potential or the application of an out-of-plane magnetic field

Confinement of long-lived interlayer excitons in WS 2 /WSe 2 heterostructures

Abstract: Interlayer excitons in layered materials constitute a novel platform to study many-body phenomena arising from long-range interactions between quantum particles. Long-lived excitons are required to achieve high particle densities, to mediate thermalisation, and to allow for spatially and temporally correlated phases. Additionally, the ability to confine them in periodic arrays is key to building a solid-state analogue to atoms in optical lattices. Here, we demonstrate interlayer excitons with lifetime approaching 0.2 ms in a layered-material heterostructure made from WS2 and WSe2 monolayers. We show that interlayer excitons can be localised in an array using a nano-patterned substrate. These confined excitons exhibit microsecond-lifetime, enhanced emission rate, and optical selection rules inherited from the host material. The combination of a permanent dipole, deterministic spatial confinement and long lifetime places interlayer excitons in a regime that satisfies one of the requirements for simulating quantum Ising models in optically resolvable lattices

Revealing emergent magnetic charge in an antiferromagnet with diamond quantum magnetometry.

Whirling topological textures play a key role in exotic phases of magnetic materials and are promising for logic and memory applications. In antiferromagnets, these textures exhibit enhanced stability and faster dynamics with respect to their ferromagnetic counterparts, but they are also difficult to study due to their vanishing net magnetic moment. One technique that meets the demand of highly sensitive vectorial magnetic field sensing with negligible backaction is diamond quantum magnetometry. Here we show that an archetypal antiferromagnet-haematite-hosts a rich tapestry of monopolar, dipolar and quadrupolar emergent magnetic charge distributions. The direct read-out of the previously inaccessible vorticity of an antiferromagnetic spin texture provides the crucial connection to its magnetic charge through a duality relation. Our work defines a paradigmatic class of magnetic systems to explore two-dimensional monopolar physics, and highlights the transformative role that diamond quantum magnetometry could play in exploring emergent phenomena in quantum materials

Revealing emergent magnetic charge in an antiferromagnet with diamond quantum magnetometry.

Acknowledgements: We thank D. M. Kara, A. Soumyanarayanan and J. J. Robinson for their useful discussions and valuable insights. Work performed at the University of Cambridge was supported by the Cambridge Nanoscale Sensing and Imaging Suite (CANSIS) as part of the Cambridge Royce facilities grant EP/P024947/1 and Sir Henry Royce Institute—recurrent grant EP/R00661X/1. We further acknowledge funding from EPSRC QUES2T (EP/N015118/1) and the Betty and Gordon Moore Foundation. Work done at the National University of Singapore was supported by the Agency for Science Technology & Research (A*STAR) under Advanced Manufacturing & Engineering Individual Research Grant (A1983c0034) and the National Research Foundation (NRF) of Singapore under its NRF-ISF joint program (grant No. NRF2020-NRFISF004-3518). Work done at the University of Oxford was supported by EPSRC grant (EP/M020517/1) and the Oxford-ShanghaiTech collaboration project. A.K.C.T. acknowledges funding from A*STAR, through the National Science Scholarship. H.J. acknowledges support from the Marie Skłodowska-Curie Postdoctoral Fellowship under the Horizon Europe Guarantee Funding from UK Research and Innovation (EP/X024938/1). M.H. acknowledges funding from EPSRC NQIT (EP/M013243/1). L.S. acknowledges funding from European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 101063285. H.S.K. acknowledges funding from the Royal Society through a University Research Fellowship.Whirling topological textures play a key role in exotic phases of magnetic materials and are promising for logic and memory applications. In antiferromagnets, these textures exhibit enhanced stability and faster dynamics with respect to their ferromagnetic counterparts, but they are also difficult to study due to their vanishing net magnetic moment. One technique that meets the demand of highly sensitive vectorial magnetic field sensing with negligible backaction is diamond quantum magnetometry. Here we show that an archetypal antiferromagnet-haematite-hosts a rich tapestry of monopolar, dipolar and quadrupolar emergent magnetic charge distributions. The direct read-out of the previously inaccessible vorticity of an antiferromagnetic spin texture provides the crucial connection to its magnetic charge through a duality relation. Our work defines a paradigmatic class of magnetic systems to explore two-dimensional monopolar physics, and highlights the transformative role that diamond quantum magnetometry could play in exploring emergent phenomena in quantum materials

Confinement of long-lived interlayer excitons in WS2/WSe2 heterostructures

Excitons are quasiparticles consisting of an electron-hole pair and can be used to study many-body phenomenon. Here, the authors demonstrate on-demand quantum confinement of long-lived interlayer excitons in WS2/WSe2 heterostructures deposited on nanopatterned substrates

Newborn metabolic vulnerability profile identifies preterm infants at risk for mortality and morbidity.

BackgroundIdentifying preterm infants at risk for mortality or major morbidity traditionally relies on gestational age, birth weight, and other clinical characteristics that offer underwhelming utility. We sought to determine whether a newborn metabolic vulnerability profile at birth can be used to evaluate risk for neonatal mortality and major morbidity in preterm infants.MethodsThis was a population-based retrospective cohort study of preterm infants born between 2005 and 2011 in California. We created a newborn metabolic vulnerability profile wherein maternal/infant characteristics along with routine newborn screening metabolites were evaluated for their association with neonatal mortality or major morbidity.ResultsNine thousand six hundred and thirty-nine (9.2%) preterm infants experienced mortality or at least one complication. Six characteristics and 19 metabolites were included in the final metabolic vulnerability model. The model demonstrated exceptional performance for the composite outcome of mortality or any major morbidity (AUC 0.923 (95% CI: 0.917-0.929). Performance was maintained across mortality and morbidity subgroups (AUCs 0.893-0.979).ConclusionsMetabolites measured as part of routine newborn screening can be used to create a metabolic vulnerability profile. These findings lay the foundation for targeted clinical monitoring and further investigation of biological pathways that may increase the risk of neonatal death or major complications in infants born preterm.ImpactWe built a newborn metabolic vulnerability profile that could identify preterm infants at risk for major morbidity and mortality. Identifying high-risk infants by this method is novel to the field and outperforms models currently in use that rely primarily on infant characteristics. Utilizing the newborn metabolic vulnerability profile for precision clinical monitoring and targeted investigation of etiologic pathways could lead to reductions in the incidence and severity of major morbidities associated with preterm birth

’Let’s Call Ourselves the Super Elite’: Using the Collective Behavior Tradition to Analyze Trump’s America

The mid‐twentieth century “collective behavior” school asserted that (1) collective behavior—the actions of crowds, movements, and other gatherings—had distinct dynamics; (2) such action was often “nonrational,” or not governed by cost‐benefit calculation; and (3) collective behavior could pose a threat to liberal democracy because of these features. While this tradition fell out of scholarly favor, the 2016 election has given us empirical reasons to revisit some elements of collective behavior approaches. We argue for three key orienting concerns, drawn from this tradition, to understand the current political era. First is a focus on authoritarianism and populism, particularly among those who feel disaffected and isolated from political institutions, pared of psychologistic determinism and geared more sensitively to their manifestations as a political style. Second is a focus on racialized resentment, strain, and perceptions of status decline, especially in how such feelings are activated when people are confronted with disruptions to their lives. Third is an analysis of “emergent norms” and the extent to which political actors produce normative understandings of contextually appropriate action that are distinct from traditional political behavior. We elaborate on these themes, apply them to examples from current politics, and suggest ways to incorporate them into contemporary sociological research