Strongly Correlated Exciton-Magnetization System for Optical Spin Pumping in CrBr3 and CrI3 .

Ferromagnetism in van der Waals systems, preserved down to a monolayer limit, attracted attention to a class of materials with general composition CrX3 (X=I, Br, and Cl), which are treated now as canonical 2D ferromagnets. Their diverse magnetic properties, such as different easy axes or varying and controllable character of in-plane or interlayer ferromagnetic coupling, make them promising candidates for spintronic, photonic, optoelectronic, and other applications. Still, significantly different magneto-optical properties between the three materials have been presenting a challenging puzzle for researchers over the last few years. Herewith, it is demonstrated that despite similar structural and magnetic configurations, the coupling between excitons and magnetization is qualitatively different in CrBr3 and CrI3 films. Through a combination of the optical spin pumping experiments with the state-of-the-art theory describing bound excitonic states in the presence of magnetization, we concluded that the hole-magnetization coupling has the opposite sign in CrBr3 and CrI3 and also between the ground and excited exciton state. Consequently, efficient spin pumping capabilities are demonstrated in CrBr3 driven by magnetization via spin-dependent absorption, and the different origins of the magnetic hysteresis in CrBr3 and CrI3 are unraveled.

ZnPSe3 as ultrabright indirect band-gap system with microsecond excitonic lifetimes.

ZnPSe3 was identified as a two-dimensional material wherein valley and spin can be optically controlled in technologically relevant timescales. We report an optical characterization of ZnPSe3 crystals that show indirect band-gap characteristics in combination with unusually strong photoluminescence. We found evidence of interband recombination from photoexcited electron-hole states with lifetimes in a microsecond timescale. Through a comparative analysis of photoluminescence and photoluminescence excitation spectra, we reconstructed the electronic band scheme relevant to fundamental processes of light absorption, carrier relaxation, and radiative recombination through interband pathways and annihilation of defect-bound excitons. The investigation of the radiative processes in the presence of a magnetic field revealed spin splitting of electronic states contributing to the ground excitonic states. Consequently, the magnetic field induces an imbalance in the number of excitons with the opposite angular momentum according to the thermal equilibrium as seen in the photoluminescence decay profiles resolved by circular polarization.

Towards practical applications of quantum emitters in boron nitride.

We demonstrate quantum emission capabilities from boron nitride structures which are relevant for practical applications and can be seamlessly integrated into a variety of heterostructures and devices. First, the optical properties of polycrystalline BN films grown by metalorganic vapour-phase epitaxy are inspected. We observe that these specimens display an antibunching in the second-order correlation functions, if the broadband background luminescence is properly controlled. Furthermore, the feasibility to use flexible and transparent substrates to support hBN crystals that host quantum emitters is explored. We characterise hBN powders deposited onto polydimethylsiloxane films, which display quantum emission characteristics in ambient environmental conditions.

Magnetic 2D materials and heterostructures.

The family of two-dimensional (2D) materials grows day by day, hugely expanding the scope of possible phenomena to be explored in two dimensions, as well as the possible van der Waals (vdW) heterostructures that one can create. Such 2D materials currently cover a vast range of properties. Until recently, this family has been missing one crucial member: 2D magnets. The situation has changed over the past 2 years with the introduction of a variety of atomically thin magnetic crystals. Here we will discuss the difference between magnetic states in 2D materials and in bulk crystals and present an overview of the 2D magnets that have been explored recently. We will focus on the case of the two most studied systems-semiconducting CrI3 and metallic Fe3GeTe2-and illustrate the physical phenomena that have been observed. Special attention will be given to the range of new van der Waals heterostructures that became possible with the appearance of 2D magnets, offering new perspectives in this rapidly expanding field.

Single photon emitters in exfoliated WSe2 structures.

Crystal structure imperfections in solids often act as efficient carrier trapping centres, which, when suitably isolated, act as sources of single photon emission. The best known examples of such attractive imperfections are well-width or composition fluctuations in semiconductor heterostructures (resulting in the formation of quantum dots) and coloured centres in wide-bandgap materials such as diamond. In the recently investigated thin films of layered compounds, the crystal imperfections may logically be expected to appear at the edges of commonly investigated few-layer flakes of these materials exfoliated on alien substrates. Here, we report comprehensive optical micro-spectroscopy studies of thin layers of tungsten diselenide (WSe2), a representative semiconducting dichalcogenide with a bandgap in the visible spectral range. At the edges of WSe2 flakes (transferred onto Si/SiO2 substrates) we discover centres that, at low temperatures, give rise to sharp emission lines (100 µeV linewidth). These narrow emission lines reveal the effect of photon antibunching, the unambiguous attribute of single photon emitters. The optical response of these emitters is inherently linked to the two-dimensional properties of the WSe2 monolayer, as they both give rise to luminescence in the same energy range, have nearly identical excitation spectra and have very similar, characteristically large Zeeman effects. With advances in the structural control of edge imperfections, thin films of WSe2 may provide added functionalities that are relevant for the domain of quantum optoelectronics.

Coherent Precession of an Individual 5/2 Spin.

We present direct observation of a coherent spin precession of an individual Mn^{2+} ion, having both electronic and nuclear spins equal to 5/2, embedded in a CdTe quantum dot and placed in a magnetic field. The spin state evolution is probed in a time-resolved pump-probe measurement of absorption of the single dot. The experiment reveals subtle details of the large-spin coherent dynamics, such as nonsinusoidal evolution of states occupation, and beatings caused by the strain-induced differences in energy levels separation. Sensitivity of the large-spin impurity on the crystal strain opens the possibility of using it as a local strain probe.

Designing quantum dots for solotronics.

Solotronics, optoelectronics based on solitary dopants, is an emerging field of research and technology reaching the ultimate limit of miniaturization. It aims at exploiting quantum properties of individual ions or defects embedded in a semiconductor matrix. It has already been shown that optical control of a magnetic ion spin is feasible using the carriers confined in a quantum dot. However, a serious obstacle was the quenching of the exciton luminescence by magnetic impurities. Here we show, by photoluminescence studies on thus-far-unexplored individual CdTe dots with a single cobalt ion and CdSe dots with a single manganese ion, that even if energetically allowed, nonradiative exciton recombination through single-magnetic-ion intra-ionic transitions is negligible in such zero-dimensional structures. This opens solotronics for a wide range of as yet unconsidered systems. On the basis of results of our single-spin relaxation experiments and on the material trends, we identify optimal magnetic-ion quantum dot systems for implementation of a single-ion-based spin memory.

The state of primary care in the United States of America and lessons for primary care groups in the United Kingdom.

The health care system of the United States of America (USA) is lavishly funded and those with adequate insurance usually receive excellent attention. However, the system is fragmented and inequitable. Health workers often find it difficult to separate vocational roles from business roles. Care tends to focus on the acute rather than the chronic, on 'episodes of illness' rather than 'person-centred' care, on short-term fixes rather than long-term approaches, on scientific/technical solutions rather than discourse or the 'art of healing', and on individual health rather than population health. The majority of US doctors are trained in the 'hightech' hospital paradigm and there is no equivalent of the United Kingdom (UK) general practitioner (GP), who lies at the hub of a primary health care team (PHCT) and who is charged with taking a long-term view, co-ordinating health care for individual patients, and acting as patient advocate without major conflicting financial incentives. However, primary care groups/trusts (PCGs) could learn from US management and training techniques, case management, NHS Direct equivalents, and the effects of poorly developed PHCTs. PCGs could develop the UK's own version of utilisation management. A cash-limited, unified budget within an underfunded National Health Service poses threats to general practice. In both the USA and the UK, primary care is a prominent tool in new attempts at cost control. PCGs offer the opportunity of better integration with public health and social services, but threaten GPs' role as independent advocates by giving them a rationing role. Managed care has forced a similar role onto our US counterparts with consequent public displeasure and professional disillusion. UK GPs will have to steer a careful course if they are to avoid a similar fate.

Recent developments in primary care in the United Kingdom: from competition to community-oriented primary care.

In 1990, changes to the National Health Service (NHS) in the United Kingdom introduced a form of US-style competition that broadened the role of general practitioners (GPs). However, the changes (called GP fundholding) produced greater inequality between practices and reduced the capacity of the NHS to plan strategically. Alternative models have been developed that retain the increased influence of primary care, promote community-oriented primary care (COPC), and facilitate strategic planning. A recent proposal from the government turns away from the competition model of 1990 to encourage GP commissioning. It offers the opportunity to create an NHS that is led by a primary care agenda, including better links with the community, and a focus on public health and social services with the goal of improving the health of populations.

Practice nurses' workload and consultation patterns.

BACKGROUND: There are calls for the role of the practice nurse to be developed and extended. Before areas for further training and education can be identified, baseline data are needed on practice nurses' current activity and workload. AIM: A study was undertaken to analyse the activity of practice nurses in two large inner city general practices and to assess the skills mix of the nursing staff required to meet the needs of the practices. METHOD: The study practices had a combined list of 26,000 patients, 80% of patients attracting a deprivation allowance. Each practice employed three practice nurses. A nurse activity index with 45 codes was constructed to describe patient-nurse consultations. Activity codes were categorized into traditional treatment tasks, extended role tasks or diagnosis and management tasks. For eight months, practice nurses in practices Y and Z recorded activity index codes for each patient consultation. Practice Y also recorded the source of referral and the age and sex of the patient. RESULTS: There were 13,898 practice nurse consultations during the study period, equivalent to an annual nurse consultation rate of 0.8 per patient. Compared with the practice population as a whole, the patients attending the practice nurses in practice Y were older (mean age 43 years versus 37 years, P < 0.001). Those attending the practice nurses in practice Y were also more likely to be female (61% of consultations were with female patients compared with 50% of the practice population as a whole, P < 0.001). In practice Y, patients referred themselves to the practice nurse in 42% of consultations, 32% were follow-up consultations and in 25% of cases the patient had been referred by a doctor. The most common reasons for nurse consultation were blood tests (15% of procedures in practice Y and 18% in practice Z) and dressings (13% in both practices). Most procedures in practices Y and Z were in the traditional treatment category (61%), 26% were in the extended role category and 9% in the diagnosis and management category (3% coded 'other', 1% uncoded). Between practices, the greatest difference in recorded procedures was for asthma check ups (7% of procedures in practice Y compared with 2% in practice Z). CONCLUSION: This study describes the workload of practice nurses in two inner city practices over eight months. Other practices could use the activity index to make comparisons over time and between practices. Up to 60% of nurses' work in the study practices could be done by a nurse without extended training and up to 30% could be done by a health care assistant, but with some loss of quality. It is suggested that half the nursing hours available to a practice should be offered by a nurse with extended training in order to undertake and develop extended role tasks and diagnosis and management tasks.

How effective is systematic care of diabetic patients? A study in one general practice.

A method of systematic diabetic care compatible with personal lists, the 'diabetic day', was introduced into a seven partner inner city general practice. The effect on glycosylated haemoglobin levels and the recording of six process measures (fundoscopy, visual acuity, weight, blood glucose levels, glycosylated haemoglobin levels and blood pressure) was assessed. Of the 111 known registered diabetic patients, 64 entered the diabetic day and fulfilled the eligibility criteria. General practice records were analysed retrospectively over a period of four years--the two years before entry into the diabetic day were compared with the subsequent two years. Mean glycosylated haemoglobin levels fell from 10.52% in the year before entry to the diabetic day to 9.71% in the second year after entry (P < 0.01, 95% confidence intervals 0.19 to 1.39). There was a significant increase in all process measures recorded in the general practice notes after entry into the diabetic day. The introduction of systematic care for diabetic patients led to an improvement in recorded process measures and a reduction in patients' glycosylated haemoglobin levels in a general practice which had made previous efforts to improve diabetic care and was already well staffed, organized and motivated.

Systematic care of diabetic patients in one general practice: how much does it cost?

This study examines the costs of running a method of systematic care for diabetic patients in one general practice--the monthly 'diabetic day'. Doctor, nurse, chiropodist, dietitian, clerical officer, building and stationery costs were included in the evaluation. The study took place in an inner city practice of seven partners based in a health centre. The cost per year of running the diabetic days was 1854.53 pounds to the practice and 4465.69 pounds to the National Health Service (1989 prices). The cost to the practice included family health services authority reimbursements and excluded the cost of the chiropodist and dietitian. The cost per attendance was 38.17 pounds to the NHS and 15.85 pounds to the practice while the cost per patient per year was 58.00 pounds to the NHS and 24.08 pounds to the practice. The practice suffered a net loss after taking into account health promotion clinic payments received from the family health services authority. The cost to the NHS of each attendance at the practice was considerably greater than estimates of the cost of attendance at the outpatients department of a local trust hospital. However, it is argued that general practice has an essential role in the improvement of diabetic surveillance, and that an adequate remuneration package could transform the care of many patients with diabetes.

Health education using video recordings in a general practice waiting area: an evaluation.

With the help of a patient participation group video recordings of health education programmes were shown in the waiting area of a health centre. Patients could choose whether or not to watch the programmes. When asked their views on the project 87% of patients responded positively, and 50% of those who watched could recall specific facts presented. There were no significant differences in age or sex between those who chose and chose not to watch the video recordings. However, unemployed patients and those in social classes 4 and 5 were significantly less likely to watch the programmes than those in social classes 1-3. The use of video recordings in both primary care and hospital waiting areas and the possible role of the health education authority as a central resource is discussed. This system could provide a useful means of extending health education, although further research is needed on the response of different social classes to different forms of health education.