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Abstract Anisotropic planar polaritons - hybrid electromagnetic modes mediated by phonons, plasmons, or excitons - in biaxial two-dimensional (2D) van der Waals crystals have attracted significant attention due to their fundamental physics and potential nanophotonic applications. In this Perspective, we review the properties of planar hyperbolic polaritons and the variety of methods that can be used to experimentally tune them. We argue that such natural, planar hyperbolic media should be fairly common in biaxial and uniaxial 2D and 1D van der Waals crystals, and identify the untapped opportunities they could enable for functional (i.e. ferromagnetic, ferroelectric, and piezoelectric) polaritons. Lastly, we provide our perspectives on the technological applications of such planar hyperbolic polaritons.

Abstract Relativistic Weyl fermion quasiparticles in Weyl semimetal bring the electron’s chirality degree of freedom into the electrical transport and give rise to exotic phenomena. A topological phase transition from a topological trivial phase to a topological non-trivial phase offers a route to control electronic devices through its topological properties. Here, we report the Weyl semimetal phase in hydrothermally grown two-dimensional Tellurium (2D Te) induced by high hydrostatic pressure (up to 2.47 GPa). The unique chiral crystal structure gives rise to chiral fermions with different topological chiral charges ( $${{C}}=-{{1}},+{{1}},{{and}}-{{2}}$$ C = − 1 , + 1 , a n d − 2 ). The highly tunable chemical potential in 2D Te provides comprehensive information for understanding the pressure-dependent electron band structure. The pressure-induced insulator-to-metal transition, two-carrier transport, and the non-trivial π Berry phase shift in quantum oscillations are observed in the 2D Te Weyl semimetal phase. Our work demonstrates the pressure-induced bandgap closing in the inversion asymmetric narrow bandgap semiconductor 2D Te.

Abstract Transition metal dichalcogenide (TMD) layered semiconductors possess immense potential in the design of photonic, electronic, optoelectronic, and sensor devices. However, the sub-bandgap light absorption of TMD in the range from near-infrared (NIR) to short-wavelength infrared (SWIR) is insufficient for applications beyond the bandgap limit. Herein, we report that the sub-bandgap photoresponse of MoS2/Au heterostructures can be robustly modulated by the electrode fabrication method employed. We observed up to 60% sub-bandgap absorption in the MoS2/Au heterostructure, which includes the hybridized interface, where the Au layer was applied via sputter deposition. The greatly enhanced absorption of sub-bandgap light is due to the planar cavity formed by MoS2 and Au; as such, the absorption spectrum can be tuned by altering the thickness of the MoS2 layer. Photocurrent in the SWIR wavelength range increases due to increased absorption, which means that broad wavelength detection from visible toward SWIR is possible. We also achieved rapid photoresponse (~150 µs) and high responsivity (17 mA W−1) at an excitation wavelength of 1550 nm. Our findings demonstrate a facile method for optical property modulation using metal electrode engineering and for realizing SWIR photodetection in wide-bandgap 2D materials.

Abstract Contrary to topological insulators, topological semimetals possess a nontrivial chiral anomaly that leads to negative magnetoresistance and are hosts to both conductive bulk states and topological surface states with intriguing transport properties for spintronics. Here, we fabricate highly-ordered metallic Pt3Sn and Pt3SnxFe1-x thin films via sputtering technology. Systematic angular dependence (both in-plane and out-of-plane) study of magnetoresistance presents surprisingly robust quadratic and linear negative longitudinal magnetoresistance features for Pt3Sn and Pt3SnxFe1-x, respectively. We attribute the anomalous negative longitudinal magnetoresistance to the type-II Dirac semimetal phase (pristine Pt3Sn) and/or the formation of tunable Weyl semimetal phases through symmetry breaking processes, such as magnetic-atom doping, as confirmed by first-principles calculations. Furthermore, Pt3Sn and Pt3SnxFe1-x show the promising performance for facilitating the development of advanced spin-orbit torque devices. These results extend our understanding of chiral anomaly of topological semimetals and can pave the way for exploring novel topological materials for spintronic devices.

Abstract Near-perfect light absorbers (NPLAs), with absorbance, $${{{{{{{\mathcal{A}}}}}}}}$$ A , of at least 99%, have a wide range of applications ranging from energy and sensing devices to stealth technologies and secure communications. Previous work on NPLAs has mainly relied upon plasmonic structures or patterned metasurfaces, which require complex nanolithography, limiting their practical applications, particularly for large-area platforms. Here, we use the exceptional band nesting effect in TMDs, combined with a Salisbury screen geometry, to demonstrate NPLAs using only two or three uniform atomic layers of transition metal dichalcogenides (TMDs). The key innovation in our design, verified using theoretical calculations, is to stack monolayer TMDs in such a way as to minimize their interlayer coupling, thus preserving their strong band nesting properties. We experimentally demonstrate two feasible routes to controlling the interlayer coupling: twisted TMD bi-layers and TMD/buffer layer/TMD tri-layer heterostructures. Using these approaches, we demonstrate room-temperature values of $${{{{{{{\mathcal{A}}}}}}}}$$ A =95% at λ=2.8 eV with theoretically predicted values as high as 99%. Moreover, the chemical variety of TMDs allows us to design NPLAs covering the entire visible range, paving the way for efficient atomically-thin optoelectronics.

Here, the authors predict that plasmons in two-dimensional materials with closely located electron and hole Fermi pockets can be amplified when an electrical current bias is applied along the displaced electron-hole pockets, without the need for an external gain medium.

Van der Waals heterostructures offer the potential of integrating multiple material layers into a single device to achieve new functionalities. Here, Ou et al combine ZrTe2, a topological semimetal, with CrTe2, a 2D ferromagnet, in a single heterostructure and demonstrate spin-orbit torque switching of the 2D ferromagnet by current in the topological semimetal.

The short exciton lifetime and strong exciton-exciton interaction in transition metal dichalcogenides limit the efficiency of exciton emission. Here, the authors show that exciton-exciton interaction in monolayer WS2 can be screened using proximal metal plates, leading to an improved quantum yield.

This review presents an overview of scenarios where van der Waals (vdW) materials provide unique advantages for nanophotonic biosensing applications. The authors discuss basic sensing principles based on vdW materials, advantages of the reduced dimensionality as well as technological challenges.

Acoustic graphene plasmons are superior to the graphene surface plasmons in field confinement and normalized propagation length, thus promising for applications. Here, the authors report near-field imaging of acoustic plasmons in high-quality CVD graphene, measure the AGP dispersion and propagation loss, and investigate their behavior in a periodic structure.

The tight confinement of polaritons in 2D materials leads to increased optical losses. Here, the authors demonstrate image phonon polariton modes in hexagonal boron nitride with an antisymmetric charge distribution that feature quality factors of up to 501 and an effective index of 132.

Identification of gas molecules is crucial in healthcare and security applications. Here the authors achieve label-free identification of SO2, NO2, N2O, and NO gas molecules by detecting their rotational-vibrational modes using graphene nanoribbon plasmons.

The capability of positioning target molecules onto the edges of patterned graphene nanostructures is highly desirable. Here, the authors demonstrate that the atomically sharp edges of graphene can be used as dielectrophoretic tweezers for gradient-force-based trapping applications.

Few-layered black phosphorus offers an infrared bandgap, complementing that of graphene and transition metal dichalcogenides. Here, the authors investigate the thickness- and strain-dependent electronic structure of black phosphorus using polarised infrared spectroscopy.

Background An advance care plan outlines a patient’s wishes regarding medical treatment or goals of care in the case that they become unable to communicate or to make decisions. An advance care directive (ACD) is an advance care plan that has been formally recorded and has legal status. Despite ACDs playing an important role in person-centred end-of-life care, an earlier retrospective medical records audit demonstrated that only 11% (58/531) of people who died due to a terminal illness had an ACD.The aim of this project was to increase the proportion of patients with a terminal illness completing an ACD. A secondary outcome was to measure the impact of ACDs on hospital and intensive care unit (ICU) admissions in the last 6 months of life.This multifaceted project comprised (1) education for health professionals and the public; (2) individual support for patients on request; (3) development of online resources for health professionals and the general public; and (4) monthly team meetings.Method The proportion of ACDs completed and hospital and ICU admissions during the last 6 months of life, were extracted via medical record audits.Written consent was required for patients to participate, including being contacted by the project team and accessing their medical records.Results 112 patients consented to participate in the project and 109 (97%) completed an ACD. There was no reduction in the average number of hospital admissions, while ICU admissions reduced from 14% (n=74) to 0%.Conclusion The targeted, multifaceted approach to education and support for completion of ACDs, resulted in a significant increase in ACD completion and a major reduction in ICU admissions.

Abstract Objective: To assess Australian quad‐related deaths during the 2011–20 period in relation to introduction of the Consumer Goods (Quad Bikes) Safety Standard 2019. Methods: All Australian quad‐related deaths retrieved through the National Coronial Information System. Results: There were 155 cases, with 116 occurring on a farm and 39 in a non‐farm context. Deaths were evenly split between work (52%) and non‐work activities, however, 66% of all farm incidents involved work. Rollovers were responsible for 59% of cases and occurred largely on farms (86%), whilst working (69%). Head injury (32%) and asphyxiation (29%) were primary causes of death. Helmet use was low (

Hexagonal boron nitride (hBN) isa natural hyperbolic material,which can also accommodate highly dispersive surface phonon-polaritonmodes. In this paper, we examine theoretically the mid-infrared opticalproperties of graphene–hBN heterostructures derived from theircoupled plasmon–phonon modes. We find that the graphene plasmoncouples differently with the phonons of the two Reststrahlen bands,owing to their different hyperbolicity. This also leads to distinctivelydifferent interaction between an external quantum emitter and theplasmon–phonon modes in the two bands, leading to substantialmodification of its spectrum. The coupling to graphene plasmons allowsfor additional gate tunability in the Purcell factor and narrow dipsin its emission spectra. [ABSTRACT FROM AUTHOR]

Abstract Background It is not known if the incidence of common cancers in Australian farm residents is different to rural non-farm or urban residents. Methods Data from farm, rural non-farm and urban participants of the 45 and Up Study cohort in New South Wales, Australia, were linked with state cancer registry data for the years 2006–2009. Directly standardised rate ratios for cancer incidence were compared for all-cancer, prostate, breast, colorectal cancer, melanoma and non-Hodgkin Lymphoma (NHL). Proportional hazards regression was used to generate incidence hazard ratios for each cancer type adjusted for relevant confounders. Results Farm women had a significantly lower all-cancer hazard ratio than rural non-farm women (1.14, 1.01–1.29). However, the lower all-cancer risk observed in farm men, was not significant when compared to rural non-farm and urban counterparts. The all-cancer adjusted hazard ratio for combined rural non-farm and urban groups compared to farm referents, was significant for men (1.08,1.01–1.17) and women (1.13, 1.04–1.23). Confidence intervals did not exclude unity for differences in risk for prostate, breast, colorectal or lung cancers, NHL or melanoma. Whilst non-significant, farm residents had considerably lower risk of lung cancer than other residents after controlling for smoking and other factors. Conclusions All-cancer risk was significantly lower in farm residents compared to combined rural non-farm and urban groups. Farm women had a significantly lower all-cancer adjusted hazard ratio than rural non-farm women. These differences appeared to be mainly due to lower lung cancer incidence in farm residents.

Recent experiments show that a substantial energy gap in graphene can be induced via patterned hydrogenation on an iridium substrate. Here, we show that the energy gap is roughly proportional to NH1/2/NCwhen disorder is accounted for, where NHand NCdenote concentrations of hydrogen and carbon atoms, respectively. The dispersion relation, obtained through calculation of the momentum-energy resolved density of states, is shown to agree with previous angle-resolved photoemission spectroscopy results. Simulations of electronic transport in finite size samples also reveal a similar transport gap, up to 1 eV within experimentally achievable NH1/2/NCvalues. [ABSTRACT FROM AUTHOR]

Graphene has been proposed as a promising material for future nanoelectronics because of its unique electronic properties. Understanding the scaling behavior of this new nanomaterial under common experimental conditions is of critical importance for developing graphene-based nanoscale devices. We present a comprehensive experimental and theoretical study on the influence of edge disorder and bulk disorder on the minimum conductivity of graphene ribbons. For the first time, we discovered a strong nonmonotonic size scaling behavior featuring a peak and saturation minimum conductivity. Through extensive numerical simulations and analysis, we are able to attribute these features to the amount of edge and bulk disorder in graphene devices. This study elucidates the quantum transport mechanisms in realistic experimental graphene systems, which can be used as a guideline for designing graphene-based nanoscale devices with improved performance. [ABSTRACT FROM AUTHOR]

Particular strain geometry in graphene could lead to a uniform pseudomagnetic field of order 10Tand might open up interesting applications in graphene nanoelectronics. Through quantum transport calculations of realistic strained graphene flakes of sizes of 100 nm, we examine possible means of exploiting this effect for practical electronics and valleytronics devices. First, we found that elastic backscattering at rough edges leads to the formation of well-defined transport gaps of order 100 meV under moderate maximum strain of 10%. Second, the application of a real magnetic field induced a separation, in space and energy, of the states arising from different valleys, leading to a way of inducing bulk valley polarization which is insensitive to short-range scattering. [ABSTRACT FROM AUTHOR]

Abstract Objective: This study compares the patterns of quad‐related fatal injuries between Australia and New Zealand (NZ). Method: Fatal injuries from July 2007 to June 2012 involving a quad (quad bike or all‐terrain vehicle) were identified from coronial files. Data described the socio‐demographic, injury, vehicle and environment factors associated with incidents. Injury patterns were compared between countries. Results: A total of 101 quad‐related fatalities were identified: 69 in Australia and 32 in NZ (7.3 and 8.0 annual fatalities per 100,000 vehicles). Of these, 95 closed cases were examined in detail and factors in common included fatalities occurring mainly in males, on farms, involving a rollover and resulting in crush injuries to the head and thorax. Helmet use and alcohol/drug involvement were infrequent. Differences were observed with regard to age, season of fatal incident and the presence of a slope. Conclusions: Fatality patterns are broadly similar. The few differences could be attributed to differing agricultural commodity mix, demographics and topography. Implications: This study's findings support harmonised cross‐country injury prevention efforts primarily focused on safe design and engineering principles to reduce this injury burden.

Abstract Objective: To examine gender differences in the characteristics, treatment costs and health outcomes of farm injuries resulting in hospitalisation of New South Wales (NSW) residents. Method: A population‐based study of individuals injured on a farm and admitted to hospital using linked hospital admission and mortality records from 1 January 2010 to 30 June 2014 in NSW. Health outcomes, including injury severity, hospital length of stay (LOS), 28‐day readmission and 30‐day mortality were examined by gender. Results: A total of 6,270 hospitalisations were identified, with males having a higher proportion of work‐related injuries and injuries involving motorbikes compared to females. Females had a higher proportion of equestrian‐related injuries. There were no differences in injury severity, with around 20% serious injuries, in mean LOS or 28‐day hospital re‐admission. Treatment costs totalled $42.7 million, with males accounting for just under 80% of the total. Conclusions: There are some gender differences in the characteristics of farm injury‐related hospitalisations. Farm injury imposes modest, but nonetheless relatively considerable, financial costs on hospital services in NSW. Implications for public health: Continued efforts to ameliorate these injuries in a farm environment, which are mainly preventable, will have personal and societal benefits.

Objectives and importance of the study: To determine whether use of selected therapies for prostate, breast and colorectal cancer in farm residents differs from that in rural nonfarm and urban counterparts. Little is known about cancer therapies used by farm residents. Study type: Data linkage cohort study. Methods: Baseline survey information from the Sax Institute’s 45 and Up Study cohort was linked with data from the New South Wales Admitted Patient Data Collection for 2006–2012. Adjusted odds of receiving surgery, chemotherapy, radiotherapy and/or brachytherapy for each cancer were compared between groups, controlling for selected variables. Results: Differences in the likelihood of surgery for breast and colorectal cancer between groups were not significant. However, for prostate cancer, farm men had 35% greater odds of prostatectomy than rural nonfarm men (odds ratio [OR] 1.35; 95% CI 1.05, 1.72). Urban men were most likely to have had brachytherapy, with three times greater odds of treatment than farm men (OR 2.90; 95% CI 1.51, 5.56). Urban women were most likely to have had chemotherapy for breast cancer, having twice the odds of receiving this treatment as farm women (OR 2.24; 95% CI 1.25, 4.04). The odds of chemotherapy for colorectal cancer among rural nonfarm residents were two-thirds the odds among urban men (OR 0.62; 95% CI 0.44, 0.90) and urban women (OR 0.57; 95% CI 0.37, 0.88). Age, distance, income and health insurance factors contributed to differences in nonsurgical care between groups. Conclusions: Cancer-related surgical services for breast and colorectal cancer were comparable between groups. Farm and rural nonfarm residents may have been disadvantaged in relation to nonsurgical therapies for prostate, breast and colorectal cancer compared with urban counterparts.

Background: Agriculture is one of the most hazardous industries in Australia. The Australian Centre for Agricultural Health and Safety is the only agency that records all non-intentional injury-related events (work and nonwork) on Australian farms. Materials and methods: Drawing on records from the National Coronial Information System, data for New South Wales (NSW), Australia, were analysed to assess cases in the 2001–2015 period. Each case was reviewed in accordance with the Farm Injury Optimal Dataset to ascertain gender, age, work relatedness and causal agents. The location of each incident was also mapped by Statistical Area Level 4. Denominator data on the number of agricultural establishments in each area and the number of workers involved in agriculture across all of NSW were sourced from the Australian Bureau of Statistics (ABS). Two-piece linear regressions using 2007 as the change point were completed to ascertain trends for the work-related cases and all deaths (work and nonwork). Differences in rates of all deaths by regions were assessed using Poisson regression models. Results: Results indicate no change in the rate of work-related deaths per 100 000 workers over the 15-year period (mean 17.3). Although there was a statistically significant reduction in all deaths (work and nonwork) per 10 000 farms through to 2007, the rate has remained stable since this time. There was no significant variation in the all-deaths rate (work and nonwork) between any of the geographic areas. Study limitations included estimations based on ABS data for the distribution of farms, the lack of data by statistical area on agricultural worker numbers and a case closure rate of 87%. Lessons learnt: There has been no improvement in work-related fatality rates in the sector in NSW for at least 15 years, and similarly no improvement in the all-injury fatality rate (work and nonwork) since 2007. Data in this study can be used to strengthen investment and revitalise the adoption of evidence based approaches that address relevant issues.

By an integral equation approach to the time-harmonic classical Maxwell equations, we describe the dispersion in the nonretarded frequency regime of the edge plasmon-polariton (EPP) on a semi-infinite flat sheet. The sheet has an arbitrary, physically admissible, tensor valued and spatially homogeneous conductivity, and serves as a model for a family of two-dimensional conducting materials. We formulate a system of integral equations for the electric field tangential to the sheet in a homogeneous and isotropic ambient medium. We show how this system is simplified via a length scale separation. This view entails the quasi-electrostatic approximation, by which the tangential electric field is replaced by the gradient of a scalar potential, . By the Wiener–Hopf method, we solve an integral equation for in some generality. The EPP dispersion relation comes from the elimination of a divergent limiting Fourier integral for at the edge. We connect the existence, or lack thereof, of the EPP dispersion relation to the index for Wiener–Hopf integral equations, an integer of topological character. We indicate that the values of this index may express an asymmetry due to the material anisotropy in the number of wave modes propagating on the sheet away from the edge with respect to the EPP direction of propagation. We discuss extensions such as the setting of two semi-infinite, coplanar sheets. Our theory forms a generalization of the treatment by Volkov and Mikhailov (1988 Sov. Phys.—JETP67 1639). [ABSTRACT FROM AUTHOR]

Abstract Objective : To determine the economic costs associated with all quad bike‐related fatalities in Australia, 2001 to 2010. Methods : A human capital approach to establish the economic costs of quad bike related fatalities to the Australian economy. The model included estimates on loss of earnings due to premature death and direct costs based on coronial records for ambulance, police, hospital, premature funeral, coronial and work safety authority investigation, and death compensation costs. All costs were calculated to 2010 dollars. Results : The estimated total economic cost associated with quad bike fatalities over this period was $288.1 million, with an average cost for each fatality of $2.3 million. When assessing the average cost of incidents between age cohorts, those aged 25–34 years had the lowest number of fatalities but had the highest average cost ($4.2 million). Conclusions : Quad bike fatalities have a significant economic impact on Australian society that is increasing. Implications : Given the high cost to society, interventions to address quad bike fatalities have the potential to be highly cost‐effective. Such interventions should focus on design approaches to improve the safety of quad bikes in terms of stability and protection in the event of a rollover. Additionally, relevant policy (e.g. no children under 16 years riding quads, no passengers) and intervention approaches (e.g. training and use of helmets) must also support the design modifications.

We explore the charged-impurity-scattering-limited mobility of electrons and holes in monolayer black phosphorus (BP), a highly anisotropic material. Taking full account of the anisotropic electronic structure in effective mass approximation, the zero-temperature momentum relaxation time and the charge carrier mobility are calculated based on the Boltzmann transport equation. For carrier densities accessible in experiments, we obtain anisotropy ratios of 3-4. These results are somewhat larger than mobility anisotropy ratios determined experimentally for multilayer BP samples, but due to the complex dependence of the scattering rates on the anisotropy, they are strikingly smaller than the effective mass ratios. [ABSTRACT FROM AUTHOR]

Graphene plasmonic nanostructures enable subwavelength confinement of electromagnetic energy from the mid-infrared down to the terahertz frequencies. By exploiting the spectrally varying light scattering phase at the vicinity of the resonant frequency of the plasmonic nanostructure, it is possible to control the angle of reflection of an incoming light beam. We demonstrate, through full-wave electromagnetic simulations based on Maxwell equations, the electrical control of the angle of reflection of a mid-infrared light beam by using an aperiodic array of graphene nanoribbons, whose widths are engineered to produce a spatially varying reflection phase profile that allows for the construction of a far-field collimated beam towards a predefined direction. [ABSTRACT FROM AUTHOR]

We propose a novel approach to achieve a giant anomalous Hall effect (AHE) in materials with flat bands (FBs). FBs are accompanied by small electronic bandwidths, which consequently increases the momentum separation (K) within pair of Weyl points and, thus, the integrated Berry curvature. Starting from a simple model with a single pair of Weyl nodes, we demonstrated the increase of K and the AHE by decreasing the bandwidth. It is further expanded to a realistic pyrochlore lattice model with characteristic double-degenerated FBs, where we discovered a giant AHE while maximizing the K with nearly vanishing band dispersion of FBs. We identify that such a model system can be realized and modulated through strain engineering in both pyrochlore and spinel compounds based on first-principles calculations, validating our theoretical model and providing a feasible platform for experimental exploration. [ABSTRACT FROM AUTHOR]