Highly confined epsilon-near-zero and surface phonon polaritons in SrTiO3 membranes.

Recent theoretical studies have suggested that transition metal perovskite oxide membranes can enable surface phonon polaritons in the infrared range with low loss and much stronger subwavelength confinement than bulk crystals. Such modes, however, have not been experimentally observed so far. Here, using a combination of far-field Fourier-transform infrared (FTIR) spectroscopy and near-field synchrotron infrared nanospectroscopy (SINS) imaging, we study the phonon polaritons in a 100 nm thick freestanding crystalline membrane of SrTiO3 transferred on metallic and dielectric substrates. We observe a symmetric-antisymmetric mode splitting giving rise to epsilon-near-zero and Berreman modes as well as highly confined (by a factor of 10) propagating phonon polaritons, both of which result from the deep-subwavelength thickness of the membranes. Theoretical modeling based on the analytical finite-dipole model and numerical finite-difference methods fully corroborate the experimental results. Our work reveals the potential of oxide membranes as a promising platform for infrared photonics and polaritonics.

Real-Space Infrared Spectroscopy of Ferroelectric Domain Walls in Multiferroic h-(Lu,Sc)FeO3.

We employ synchrotron-based near-field infrared spectroscopy to image the phononic properties of ferroelectric domain walls in hexagonal (h) Lu0.6Sc0.4FeO3, and we compare our findings with a detailed symmetry analysis, lattice dynamics calculations, and prior models of domain-wall structure. Rather than metallic and atomically thin as observed in the rare-earth manganites, ferroelectric walls in h-Lu0.6Sc0.4FeO3 are broad and semiconducting, a finding that we attribute to the presence of an A-site substitution-induced intermediate phase that reduces strain and renders the interior of the domain wall nonpolar. Mixed Lu/Sc occupation on the A site also provides compositional heterogeneity over micron-sized length scales, and we leverage the fact that Lu and Sc cluster in different ratios to demonstrate that the spectral characteristics at the wall are robust even in different compositional regimes. This work opens the door to broadband imaging of physical and chemical heterogeneity in ferroics and represents an important step toward revealing the rich properties of these flexible defect states.

Ultrahigh-Quality Infrared Polaritonic Resonators Based on Bottom-Up-Synthesized van der Waals Nanoribbons.

van der Waals nanomaterials supporting phonon polariton quasiparticles possess extraordinary light confinement capabilities, making them ideal systems for molecular sensing, thermal emission, and subwavelength imaging applications, but they require defect-free crystallinity and nanostructured form factors to fully showcase these capabilities. We introduce bottom-up-synthesized α-MoO3 structures as nanoscale phonon polaritonic systems that feature tailorable morphologies and crystal qualities consistent with bulk single crystals. α-MoO3 nanoribbons serve as low-loss hyperbolic Fabry-Pérot nanoresonators, and we experimentally map hyperbolic resonances over four Reststrahlen bands spanning the far- and mid-infrared spectral range, including resonance modes beyond the 10th order. The measured quality factors are the highest from phonon polaritonic van der Waals structures to date. We anticipate that bottom-up-synthesized polaritonic van der Waals nanostructures will serve as an enabling high-performance and low-loss platform for infrared optical and optoelectronic applications.

Discovery of davemaoite, CaSiO3-perovskite, as a mineral from the lower mantle.

Calcium silicate perovskite, CaSiO3, is arguably the most geochemically important phase in the lower mantle, because it concentrates elements that are incompatible in the upper mantle, including the heat-generating elements thorium and uranium, which have half-lives longer than the geologic history of Earth. We report CaSiO3-perovskite as an approved mineral (IMA2020-012a) with the name davemaoite. The natural specimen of davemaoite proves the existence of compositional heterogeneity within the lower mantle. Our observations indicate that davemaoite also hosts potassium in addition to uranium and thorium in its structure. Hence, the regional and global abundances of davemaoite influence the heat budget of the deep mantle, where the mineral is thermodynamically stable.

Laser-Induced Cooperative Transition in Molecular Electronic Crystal.

The competing and non-equilibrium phase transitions, involving dynamic tunability of cooperative electronic and magnetic states in strongly correlated materials, show great promise in quantum sensing and information technology. To date, the stabilization of transient states is still in the preliminary stage, particularly with respect to molecular electronic solids. Here, a dynamic and cooperative phase in potassium-7,7,8,8-tetracyanoquinodimethane (K-TCNQ) with the control of pulsed electromagnetic excitation is demonstrated. Simultaneous dynamic and coherent lattice perturbation with 8 ns pulsed laser (532 nm, 15 MW cm-2 , 10 Hz) in such a molecular electronic crystal initiates a stable long-lived (over 400 days) conducting paramagnetic state (≈42 Ωcm), showing the charge-spin bistability over a broad temperature range from 2 to 360 K. Comprehensive noise spectroscopy, in situ high-pressure measurements, electron spin resonance (ESR), theoretical model, and scanning tunneling microscopy/spectroscopy (STM/STS) studies provide further evidence that such a transition is cooperative, requiring a dedicated charge-spin-lattice decoupling to activate and subsequently stabilize nonequilibrium phase. The cooperativity triggered by ultrahigh-strain-rate (above 106 s- 1 ) pulsed excitation offers a collective control toward the generation and stabilization of strongly correlated electronic and magnetic orders in molecular electronic solids and offers unique electro-magnetic phases with technological promises.

Probing subwavelength in-plane anisotropy with antenna-assisted infrared nano-spectroscopy.

Infrared nano-spectroscopy based on scattering-type scanning near-field optical microscopy (s-SNOM) is commonly employed to probe the vibrational fingerprints of materials at the nanometer length scale. However, due to the elongated and axisymmetric tip shank, s-SNOM is less sensitive to the in-plane sample anisotropy in general. In this article, we report an easy-to-implement method to probe the in-plane dielectric responses of materials with the assistance of a metallic disk micro-antenna. As a proof-of-concept demonstration, we investigate here the in-plane phonon responses of two prototypical samples, i.e. in (100) sapphire and x-cut lithium niobate (LiNbO3). In particular, the sapphire in-plane vibrations between 350 cm-1 to 800 cm-1 that correspond to LO phonon modes along the crystal b- and c-axis are determined with a spatial resolution of < λ/10, without needing any fitting parameters. In LiNbO3, we identify the in-plane orientation of its optical axis via the phonon modes, demonstrating that our method can be applied without prior knowledge of the crystal orientation. Our method can be elegantly adapted to retrieve the in-plane anisotropic response of a broad range of materials, i.e. subwavelength microcrystals, van-der-Waals materials, or topological insulators.

Impact of a Respiratory Disease Young Investigators' Forum on the Career Development of Physician-Scientists.

Background: To reverse the dramatic decline in the U.S. physician-scientist workforce, interventions are necessary to retain physicians in research careers.Objective: To evaluate the impact of an annual 3-day symposium, the Respiratory Disease Young Investigators' Forum (RDYIF), designed to guide fellows and junior faculty into successful physician-scientist careers.Methods: In this retrospective, observational study, a questionnaire was e-mailed to 308 physicians who participated in the RDYIF between 2005 and 2018. The questionnaire was administered by National Jewish Health study personnel in the spring of 2019. Responses were primarily analyzed using descriptive and qualitative approaches.Results: The response rate was 39.3% (n = 121), with 107 of responders (88.4%) completing the full survey. The majority of survey completers currently worked as physician-scientists (76.6%; n = 82), held faculty positions (88.8%; n = 95) in an academic center (90.6%; n = 97), and were currently involved in research (93.4%; n = 100). The majority had been an author on ≥10 peer-reviewed publications (61.3%, n = 65) and had been awarded research grants (71.7%; n = 76). Thirty completers (28.3%) had served as a principal investigator on one or more clinical trials. Completers indicated that participation in the RDYIF had a "strong impact" or "very strong impact" on their career development as physician-scientists.Conclusion: Participation in the RDYIF strengthened participants' interest in physician-scientist careers and appeared to track with successful career development. Young Investigator Forums such as the RDYIF may be an effective intervention to support the declining supply of physician-scientists in North America.

Idiopathic pulmonary fibrosis: Educational needs of health-care providers, patients, and caregivers.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease associated with poor quality of life. Debilitating symptoms and the reality of shortened survival impact patients' physical and emotional well-being and constrain the lives of patients' caregivers. This study assessed the informational needs of medical providers who care for patients with IPF, IPF patients themselves, and their caregivers. Tailored surveys were sent electronically to providers, patients with IPF, and caregivers of patients with IPF collected on a rolling basis in March of 2017. Providers answered questions regarding their own informational needs and what information they believed patients needed. Patients and caregivers identified their own informational needs and the perceived needs for each other. About 2636 surveys were sent to providers, including 2041 to physicians, of whom 156 completed it. One hundred sixty patients and 29 caregivers responded to the survey via a link on a website. Eighty-six percent of providers described themselves as physicians who diagnose and treat IPF patients themselves. Providers ranked information on "making the diagnosis of IPF" as their top informational need. Patients and caregivers chose "disease progression/what to expect" as the most important informational need for themselves and for each other. Providers want to make a correct diagnosis when IPF is in the differential diagnosis. Patients and caregivers desire clarity around how IPF will behave over time and what their futures with IPF will look like. Resources for patients and their caregivers should include information on disease natural history in empathically worded, clear, and easily accessible formats.

Phase-Change Hyperbolic Heterostructures for Nanopolaritonics: A Case Study of hBN/VO2.

Unlike conventional plasmonic media, polaritonic van der Waals (vdW) materials hold promise for active control of light-matter interactions. The dispersion relations of elementary excitations such as phonons and plasmons can be tuned in layered vdW systems via stacking using functional substrates. In this work, infrared nanoimaging and nanospectroscopy of hyperbolic phonon polaritons are demonstrated in a novel vdW heterostructure combining hexagonal boron nitride (hBN) and vanadium dioxide (VO2 ). It is observed that the insulator-to-metal transition in VO2 has a profound impact on the polaritons in the proximal hBN layer. In effect, the real-space propagation of hyperbolic polaritons and their spectroscopic resonances can be actively controlled by temperature. This tunability originates from the effective change in local dielectric properties of the VO2 sublayer in the course of the temperature-tuned insulator-to-metal phase transition. The high susceptibility of polaritons to electronic phase transitions opens new possibilities for applications of vdW materials in combination with strongly correlated quantum materials.

Multicolor T-Ray Imaging Using Multispectral Metamaterials.

Recent progress in ultrafast spectroscopy and semiconductor technology is enabling unique applications in screening, detection, and diagnostics in the Terahertz (T-ray) regime. The promise of efficaciously operation in this spectral region is tempered by the lack of devices that can spectrally analyze samples at sufficient temporal and spatial resolution. Real-time, multispectral T-ray (Mul-T) imaging is reported by designing and demonstrating hyperspectral metamaterial focal plane array (MM-FPA) interfaces allowing multiband (and individually tunable) responses without compromising on the pixel size. These MM-FPAs are fully compatible with existing microfabrication technologies and have low noise when operating in the ambient environment. When tested with a set of frequency switchable quantum cascade lasers (QCLs) for multicolor illumination, both MM-FPAs and QCLs can be tuned to operate at multiple discrete THz frequencies to match analyte "fingerprints." Versatile imaging capabilities are presented, including unambiguous identification of concealed substances with intrinsic and/or human-engineered THz characteristics as well as effective diagnosis of cancerous tissues without notable spectral signatures in the THz range, underscoring the utility of applying multispectral approaches in this compelling wavelength range for sensing/identification and medical imaging.

Protein Bricks: 2D and 3D Bio-Nanostructures with Shape and Function on Demand.

Precise patterning of polymer-based biomaterials for functional bio-nanostructures has extensive applications including biosensing, tissue engineering, and regenerative medicine. Remarkable progress is made in both top-down (based on lithographic methods) and bottom-up (via self-assembly) approaches with natural and synthetic biopolymers. However, most methods only yield 2D and pseudo-3D structures with restricted geometries and functionalities. Here, it is reported that precise nanostructuring on genetically engineered spider silk by accurately directing ion and electron beam interactions with the protein's matrix at the nanoscale to create well-defined 2D bionanopatterns and further assemble 3D bionanoarchitectures with shape and function on demand, termed "Protein Bricks." The added control over protein sequence and molecular weight of recombinant spider silk via genetic engineering provides unprecedented lithographic resolution (approaching the molecular limit), sharpness, and biological functions compared to natural proteins. This approach provides a facile method for patterning and immobilizing functional molecules within nanoscopic, hierarchical protein structures, which sheds light on a wide range of biomedical applications such as structure-enhanced fluorescence and biomimetic microenvironments for controlling cell fate.

Understanding the informational needs of patients with IPF and their caregivers: 'You get diagnosed, and you ask this question right away, what does this mean?'

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive, incurable lung disease whose intrusive symptoms rob patients of their quality of life. Patients with IPF rely on their caregivers for support and assistance in amounts that vary according to patients' individual circumstances and disease severity. Knowledgeable and well-informed patients and caregivers are best suited to deal with life-altering conditions like IPF. METHODS: We conducted two hour-long focus groups with 13 patients with IPF and 4 caregivers of patients with IPF to better understand their informational needs and in what format such information should be delivered. RESULTS: Patients discussed the challenges IPF creates in their daily lives. They wanted information on how to live well despite having IPF, practical information on how they could remain active and travel and how they could preserve their quality of life despite living with a life-threatening disease like IPF. Caregivers wanted information on the general aspects of IPF, because it would help them understand what patients were going through. They also wanted specific information on how to give care to a patient with IPF, even when physical care may not be needed (as in earlier phases of the disease). Patients and caregivers both needed efficient information delivery from trustworthy sources, including the healthcare team involved in their care. They considered both spoken and written information valuable, and ease of access was critical. CONCLUSION: This study provides valuable insight regarding the informational needs of IPF patients and their caregivers. It is hoped that identifying or creating sources of this information, and insuring that patients and caregivers have access to it, will improve well-being for patients with IPF and their caregivers.

Near-field spectroscopic investigation of dual-band heavy fermion metamaterials.

Broadband tunability is a central theme in contemporary nanophotonics and metamaterials research. Combining metamaterials with phase change media offers a promising approach to achieve such tunability, which requires a comprehensive investigation of the electromagnetic responses of novel materials at subwavelength scales. In this work, we demonstrate an innovative way to tailor band-selective electromagnetic responses at the surface of a heavy fermion compound, samarium sulfide (SmS). By utilizing the intrinsic, pressure sensitive, and multi-band electron responses of SmS, we create a proof-of-principle heavy fermion metamaterial, which is fabricated and characterized using scanning near-field microscopes with <50 nm spatial resolution. The optical responses at the infrared and visible frequency ranges can be selectively and separately tuned via modifying the occupation of the 4f and 5d band electrons. The unique pressure, doping, and temperature tunability demonstrated represents a paradigm shift for nanoscale metamaterial and metasurface design.

Probing optical anisotropy of nanometer-thin van der waals microcrystals by near-field imaging.

Most van der Waals crystals present highly anisotropic optical responses due to their strong in-plane covalent bonding and weak out-of-plane interactions. However, the determination of the polarization-dependent dielectric constants of van der Waals crystals remains a nontrivial task, since the size and dimension of the samples are often below or close to the diffraction limit of the probe light. In this work, we apply an optical nano-imaging technique to determine the anisotropic dielectric constants in representative van der Waals crystals. Through the study of both ordinary and extraordinary waveguide modes in real space, we are able to quantitatively determine the full dielectric tensors of nanometer-thin molybdenum disulfide and hexagonal boron nitride microcrystals, the most-promising van der Waals semiconductor and dielectric. Unlike traditional reflection-based methods, our measurements are reliable below the length scale of the free-space wavelength and reveal a universal route for characterizing low-dimensional crystals with high anisotropies.

The Use of Functionalized Silk Fibroin Films as a Platform for Optical Diffraction-Based Sensing Applications.

A set of biocompatible, biodegradable, and biofunctionalizable diffractive optical elements (DOEs) using silk proteins as the building materials is reported. The diffraction pattern of a DOE is highly sensitive to the surrounding environment and the structural integrity, offering numerous opportunities for biosensing applications.

Nanoscale probing of electron-regulated structural transitions in silk proteins by near-field IR imaging and nano-spectroscopy.

Silk protein fibres produced by silkworms and spiders are renowned for their unparalleled mechanical strength and extensibility arising from their high-ß-sheet crystal contents as natural materials. Investigation of ß-sheet-oriented conformational transitions in silk proteins at the nanoscale remains a challenge using conventional imaging techniques given their limitations in chemical sensitivity or limited spatial resolution. Here, we report on electron-regulated nanoscale polymorphic transitions in silk proteins revealed by near-field infrared imaging and nano-spectroscopy at resolutions approaching the molecular level. The ability to locally probe nanoscale protein structural transitions combined with nanometre-precision electron-beam lithography offers us the capability to finely control the structure of silk proteins in two and three dimensions. Our work paves the way for unlocking essential nanoscopic protein structures and critical conditions for electron-induced conformational transitions, offering new rules to design protein-based nanoarchitectures.