The integration of inorganic materials in perovskite solar cells (PSCs) is critical for enhancing long-term operational stability, scalability, and economic viability. Here, we demonstrate the transformational efficacy of using a modified protocol for sputtered nickel oxide as a hole transport layer (HTL) in n-i-p structured PSCs, in conjunction with a thin Spiro-OMeTAD buffer layer. The introduction of a biased grid and a buffer interface enable us to achieve a soft landing of NiO on the halide perovskite, thereby minimizing process-induced interfacial damage. Our results indicate that the buffer layer serves solely as an interfacial protection layer, rather than as a functional HTL. Using this approach, we report champion power conversion efficiencies of 23.45% (mean approximate to 22.2%) on rigid glass substrates and 22.1% (mean approximate to 21%) on flexible ITO-coated PET substrates, both employing fully inorganic charge transport layers. These results represent unprecedented enhancements over previously reported highest PCE values (<12%) for n-i-p devices using sputtered NiO as the HTL, placing them on par with p-i-n architectures that utilize a combination of NiO and organic HTLs. This work demonstrates a scalable, commercially viable pathway toward high-efficiency, stable perovskite photovoltaics based solely on sputtered inorganic layers, offering a competitive edge for further development.

BACKGROUND:Vascular endothelial growth factor inhibitors (VEGFIs) are effective anticancer agents, but are associated with cancer therapy-related cardiac dysfunction (CTRCD) and hypertension. The timing, frequency and magnitude of these toxicities are poorly defined. The objective of this study is therefore to investigate the incidence, time course and mechanisms of VEGFI-associated CTRCD and hypertension. METHODS:Patients commencing VEGFI underwent blood pressure (BP) monitoring, echocardiography and cardiac biomarker measurement at baseline and prospectively over 24 weeks. Serial adenosine stress perfusion cardiovascular MRI (CMR) was performed in a substudy. CTRCD was defined as left ventricular ejection fraction (LVEF) decline by ≥10 percentage points from baseline to a value <50%. RESULTS:78 patients participated (68% men; age 63±11 years). 15 patients (19%) developed CTRCD, and it was evident at 4 weeks in 93% of cases. Overall, LVEF was 4.2% (95% CI: -6.2% to -2.3%, p<0.001) lower than baseline at 4 weeks. At 4 weeks, N-terminal pro-brain natriuretic peptide, but not troponin, was higher in patients with CTRCD. 62 (77%) patients developed hypertension. Home systolic and diastolic BP increased by 7.2 mm Hg (4.7-9.8, p<0.001) and 4.8 mm Hg (3.1-6.5, p<0.001), respectively, at 1 week. There was no association between change in LVEF and BP.CMR-derived LVEF, T1 relaxation times and resting myocardial blood flow (n=46) were 5.2% (-7.3% to -3.1%, p<0.001), 27 ms (-40 to -14, p<0.001) and 14.7 mL/100mL/min (-24.2 to -5.1, p=0.004), respectively, lower at 4 weeks. CONCLUSION:VEGFI-associated CTRCD is frequent and occurs early. This finding has implications for prioritising early cardiac imaging follow-up after commencing treatment. Underlying mechanisms include myocardial and microvascular effects that are at least partly independent of hypertension.

Using radio frequency magnetron sputter deposition to apply metal oxide thin film as a hole transporting layer (HTL) onto a halide perovskite layer significantly compromises the device photovoltaic performance. Therefore, despite its economic advantages and scalability potential, this method is generally not favored. Herein, we identify the primary cause of this limitation as the loss of the organic moiety from the near-interface region during the sputter deposition of NiO onto the halide perovskite and the consequent generation of interfacial defects. Furthermore, we show that a self-healing process, without any external intervention, is able to significantly compensate for the adverse effects of the sputtering process, resulting in the device efficiency to 180-220% of its initial value and leading to the highest-ever power conversion efficiency (PCE) reported for an n-i-p device with a sputtered NiO HTL. Employing optical and impedance spectroscopies, we investigate the mechanism of this self-healing process, establishing the dynamics of the process to be thermally controlled and independent of the storage ambient, indicating the diffusion of the ionic species from the bulk to the interface as the driving force for the recovery.

High-throughput fabrication of metal oxide thin films is always a bottleneck for solution-processed perovskite solar cells. Here, we report a rapid photonic curing process, with a well-controlled train of short light pulses, to develop bilayer (colloidal and blocking layer) SnO2 thin films used as electron transport layers in perovskite ((FA0.83MA0.17)0.95Cs0.05PbI2.5Br0.5, 1.62 eV band gap) photovoltaic devices (n-i-p architecture) with an optimized efficiency of 21.1% alongside good ambient and operational (MPPT) stability. The strong dependency of the photonic curing pulse parameters on device properties is investigated, and we established a corroboration between the chemical properties of the as-cured SnO2 and the optoelectronic performance of the devices and the interface quality. Furthermore, we show that the futile removal of the chloride species in photonically cured SnO2 is an added advantage against the thermally annealed ones regarding charge transport and lower interfacial recombination. Furthermore, the process is impeccably scaled up to demonstrate a series-connected minimodule (16 cm2) with 18.2% efficiency.

Despite having long excited carrier lifetimes and high mobilities in hybrid halide perovskite materials, conventional (n-i-p) devices exhibit significant interfacial nonradiative recombination losses that are little understood but limit the radiative efficiency and the overall open-circuit potential. In this Letter, we reveal that the process of spiro-OMeTAD coating on perovskite gives rise to buried defect states, which are detrimental to the devices' operational stability. We subsequently report a method to passivate these deleterious buried defect states by atomic layer deposition of Al2O3 through controlled precursor dosages on fully functional devices. The process results in notable improvements in the overall device performance, but the underlying root-cause analysis is what we essentially aimed to elucidate here. The reported passivation technique results in (a) an increase in the efficiency primarily due to an increase of VOC by similar to 60-70 mV and consequently (b) enhanced photoluminescence and higher electroluminescence quantum efficiency and (c) overall device operational (MPPT) stability under ambient and, exclusively, even under high vacuum (>300 h) conditions, which is otherwise challenging.

To determine if golden-angle radial sparse parallel (GRASP) dynamic contrast-enhanced (DCE)-MRI allows simultaneous evaluation of perfusion and morphology in liver fibrosis. Participants who were scheduled for liver biopsy or resection were enrolled (NCT02480972). Images were reconstructed at 12-s temporal resolution for morphologic assessment and at 3.3-s temporal resolution for quantitative evaluation. The image quality of the morphologic images was assessed on a four-point scale, and the Liver Imaging Reporting and Data System score was recorded for hepatic observations. Comparisons were made between quantitative parameters of DCE-MRI for the different fibrosis stages, and for hepatocellular carcinoma (HCCs) with different LR features. DCE-MRI of 64 participants (male = 48) were analyzed. The overall image quality consistently stood at 3.5 ± 0.4 to 3.7 ± 0.4 throughout the exam. Portal blood flow significantly decreased in participants with F2–F3 (n = 18, 175 ± 110 mL/100 mL/min) and F4 (n = 12, 98 ± 47 mL/100 mL/min) compared with those in participants with F0–F1 (n = 34, 283 ± 178 mL/100 mL/min, p < 0.05 for all). In participants with F4, the arterial fraction and extracellular volume were significantly higher than those in participants with F0–F1 and F2–F3 (p < 0.05). Compared with HCCs showing non-LR-M features (n = 16), HCCs with LR-M (n = 5) had a significantly prolonged mean transit time and lower arterial blood flow (p < 0.05). Liver MRI using GRASP obtains both sufficient spatial resolution for confident diagnosis and high temporal resolution for pharmacokinetic modeling. Significant differences were found between the MRI-derived portal blood flow at different hepatic fibrosis stages.

Er3+-Yb3+ co-doped NaGd(MoO4)(2) phosphors with different concentrations of Er3+ and Yb3+ ions have been successfully synthesized via a high-temperature solid-state reaction method. Phase confirmation and morphological studies have been done with the help of XRD and FESEM, respectively. The suitability of being a good host material with a high refractive index has been confirmed by the diffuse reflectance study. Intense green upconversion (UC) emission has been witnessed even with the naked-eye under a relatively low pump power of a 980 nm CW diode laser excitation source. Good thermometric properties such as absolute sensitivity up to 0.053 K-1 and relative sensitivity up to 0.014 K-1 with temperature resolution of similar to 0.37 K have been attained with the Stark sublevels of the thermally coupled transitions (i.e., H-2(11/2), S-4(3/2) -> I-4(15/2) level) of Er3+ ions. The reliability test of the temperature sensing ability and excellent thermal stability further confirm that the prepared phosphor can act as a worthy temperature probe.

Background Post hepatectomy liver failure (PHLF) remains a significant risk in patients undergoing curative liver resection for cancer, however currently available PHLF risk prediction investigations are not sufficiently accurate. The Hepatectomy risk assessment with functional magnetic resonance imaging trial (HEPARIM) aims to establish if quantitative MRI biomarkers of liver function & perfusion can be used to more accurately predict PHLF risk and FLR function, measured against indocyanine green (ICG) liver function test. Methods HEPARIM is an observational cohort study recruiting patients undergoing liver resection of 2 segments or more, prior to surgery patients will have both Dynamic Gadoxetate-enhanced (DGE) liver MRI and ICG testing. Day one post op ICG testing is repeated and R15 compared to the Gadoxetate Clearance (GC) of the future liver remnant (FLR-GC) as measure by preoperative DGE- MRI which is the primary outcome, and preoperative ICG R15 compared to GC of whole liver (WL-GC) as a secondary outcome. Data will be collected from medical records, biochemistry, pathology and radiology reports and used in a multi-variate analysis to the value of functional MRI and derive multivariant prediction models for future validation. Discussion If successful, this test will potentially provide an efficient means to quantitatively assess FLR function and PHLF risk enabling surgeons to push boundaries of liver surgery further while maintaining safe practice and thereby offering chance of cure to patients who would previously been deemed inoperable. MRI has the added benefit of already being part of the routine diagnostic pathway and as such would have limited additional burden on patients time or cost to health care systems. ( Hepatectomy Risk Assessment With Functional Magnetic Resonance Imaging - Full Text View - ClinicalTrials.gov , n.d.) Trial registration ClinicalTrials.gov, ClinicalTrials.gov NCT04705194 - Registered 12th January 2021 – Retrospectively registered

European Journal of Heart FailureVolume 22, Issue 7 p. 1276-1277 Research LetterOpen Access Cardiotoxicity and myocardial hypoperfusion associated with anti-vascular endothelial growth factor therapies: prospective cardiac magnetic resonance imaging in patients with cancer Stephen J.H. Dobbin, Stephen J.H. Dobbin BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorKenneth Mangion, Kenneth Mangion BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorColin Berry, Colin Berry BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorGiles Roditi, Giles Roditi Department of Radiology, Glasgow Royal Infirmary, Glasgow, UKSearch for more papers by this authorSusmita Basak, Susmita Basak Division of Medical Physics, University of Leeds, Leeds, UKSearch for more papers by this authorSteven Sourbron, Steven Sourbron Department of Infection, Immunity, and Cardiovascular Disease, University of Sheffield, Sheffield, UKSearch for more papers by this authorJeff White, Jeff White Institute of Cancer Sciences, University of Glasgow, Beatson West of Scotland Cancer Centre, Glasgow, UKSearch for more papers by this authorBalaji Venugopal, Balaji Venugopal Institute of Cancer Sciences, University of Glasgow, Beatson West of Scotland Cancer Centre, Glasgow, UKSearch for more papers by this authorRhian M. Touyz, Rhian M. Touyz BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorRobert J. Jones, Robert J. Jones Institute of Cancer Sciences, University of Glasgow, Beatson West of Scotland Cancer Centre, Glasgow, UKSearch for more papers by this authorMark C. Petrie, Mark C. Petrie BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorNinian N. Lang, Corresponding Author Ninian N. Lang ninian.lang@glasgow.ac.uk BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK Email: ninian.lang@glasgow.ac.ukSearch for more papers by this author Stephen J.H. Dobbin, Stephen J.H. Dobbin BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorKenneth Mangion, Kenneth Mangion BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorColin Berry, Colin Berry BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorGiles Roditi, Giles Roditi Department of Radiology, Glasgow Royal Infirmary, Glasgow, UKSearch for more papers by this authorSusmita Basak, Susmita Basak Division of Medical Physics, University of Leeds, Leeds, UKSearch for more papers by this authorSteven Sourbron, Steven Sourbron Department of Infection, Immunity, and Cardiovascular Disease, University of Sheffield, Sheffield, UKSearch for more papers by this authorJeff White, Jeff White Institute of Cancer Sciences, University of Glasgow, Beatson West of Scotland Cancer Centre, Glasgow, UKSearch for more papers by this authorBalaji Venugopal, Balaji Venugopal Institute of Cancer Sciences, University of Glasgow, Beatson West of Scotland Cancer Centre, Glasgow, UKSearch for more papers by this authorRhian M. Touyz, Rhian M. Touyz BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorRobert J. Jones, Robert J. Jones Institute of Cancer Sciences, University of Glasgow, Beatson West of Scotland Cancer Centre, Glasgow, UKSearch for more papers by this authorMark C. Petrie, Mark C. Petrie BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UKSearch for more papers by this authorNinian N. Lang, Corresponding Author Ninian N. Lang ninian.lang@glasgow.ac.uk BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK Email: ninian.lang@glasgow.ac.ukSearch for more papers by this author First published: 07 May 2020 https://doi.org/10.1002/ejhf.1847Citations: 4AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat By interrupting tumour angiogenesis, vascular endothelial growth factor signalling pathway inhibitors (VSPIs) represent a major advance in the treatment of a wide variety of cancers.1 However, their oncological benefits have been accompanied by considerable cardiovascular toxicity, including hypertension, left ventricular systolic dysfunction (LVSD) and heart failure.2 These may be severe and can limit the dose and duration of anti-cancer treatment. The timing, frequency, and pathophysiological basis of VSPI-associated myocardial toxicity is incompletely defined. In addition to the detrimental effect of an abrupt rise in left ventricular afterload as a result of VSPI-associated hypertension, inhibition of vascular endothelial growth factor may have direct myocardial toxic effects. This may be the consequence of inhibition of tyrosine kinases required both for tumour growth and normal cardiac function. Furthermore, VSPIs are associated with peripheral microvascular rarefaction3 and it remains unclear whether myocardial micro-arterial constriction or vessel loss is implicated in the pathogenesis of VSPI-associated LVSD. The only prior study to evaluate prospectively the effects of VSPIs upon cardiac function used echocardiography and demonstrated a 9.7% incidence of cardiotoxicity, defined as ≥10% reduction in left ventricular ejection fraction (LVEF) to a value less than 50%.4 There are inherent limitations of echocardiography for the reproducible detection of changes in myocardial function and it does not allow assessment of myocardial perfusion, vascular permeability, or myocardial tissue characterisation. We therefore used multi-parametric cardiac magnetic resonance imaging, including adenosine stress-perfusion to measure myocardial blood flow and vascular permeability in patients before and during VSPI treatment.5 All patients over the age of 18 years at the Beatson West of Scotland Cancer Centre in Glasgow, Scotland, who were planned to commence VSPI therapy were considered for participation. Enrolment took place between December 2018 and March 2019. Exclusion criteria included an estimated glomerular filtration rate < 30 mL/min/1.73 m2 of body surface area, persistent or permanent atrial fibrillation, second- or third-degree atrioventricular block, and a history of allergy to adenosine or gadolinium contrast. Patients underwent stress-perfusion cardiac magnetic resonance imaging (3.0T Siemens MAGNETOM Prisma; Siemens Healthcare, Erlangen, Germany) at baseline and after 4 to 6 weeks of treatment. Biventricular mass and function, myocardial feature-tracking strain, and tissue characterisation by T1 mapping and perfusion imaging were assessed. Myocardial T1 mapping measures the myocardial longitudinal magnetic relaxation time (also known as spin–lattice relaxation time) of different molecules found within the myocardium. Intravenous adenosine infusion was used to induce hyperaemia to simulate myocardial stress. Ten patients were enrolled. All had incurable cancer. One withdrew because of severe tumour-related symptoms. The average age was 60.8 ± 7.5 years and most participants were male (n = 7). Eight had renal cell cancer and one patient had sarcoma. VSPI therapies included pazopanib (n = 6), sunitinib (n = 2) and tivozanib (n = 1). Cardiovascular comorbidities were common at baseline, including hypertension (56%) and hypercholesterolaemia (22%). The average body mass index was 29.3 ± 4.4 kg/m2. Eight patients (89%) developed new or worsening hypertension with VSPI therapy. Both systolic and diastolic blood pressure increased after 4 weeks of treatment by 27.6 ± 22.0 mmHg (P = 0.006) and 18.8 ± 11.2 mmHg (P = 0.001), respectively. After 4 weeks of VSPI treatment, LVEF fell from 55.9 ± 3.1% to 51.0 ± 3.8% (P = 0.019) and five patients had a reduction in LVEF of at least 5% (Figure 1A). Myocardial T1 relaxation times reduced from 1239 ms [interquartile range (IQR) 1222–1247 ms] at baseline, to 1165 ms (IQR 1147–1222 ms) at follow-up (P = 0.038). Extra-cellular volume also declined from 26.9 ± 1.2% to 24.4 ± 1.0% (P = 0.047) at 4–6 weeks (Figure 1B and 1C). After 4–6 weeks, resting myocardial blood flow was 18% lower than baseline (P = 0.002) (Figure 1D) but adenosine-induced stress myocardial blood flow was unchanged by VSPI treatment (P = 0.152). Additionally, after 4–6 weeks, there was an increase in contrast agent extraction fraction (a marker of vascular permeability) at rest (P = 0.041), with no change during adenosine-induced stress (P = 0.772) (Figure 1E and 1F). Figure 1Open in figure viewerPowerPoint Changes in (A) left ventricular ejection fraction, (B) T1 relaxation time, (C) extracellular volume, (D) myocardial blood flow at rest and (E) stress, and (F) vascular permeability at rest with 4–6 weeks of vascular endothelial growth factor signalling pathway inhibitor therapy. In this hypothesis-generating study, VSPI therapy was associated with a reduction in LVEF and it is possible that the incidence of a more substantial drop in LVEF decline may be greater than previously appreciated. Although systemic hypertension may contribute to these phenomena, alterations in myocardial tissue characteristics, including reduced T1 relaxation time, may reflect direct myocardial toxic effects. The observed rise in vascular permeability supports a role for microvascular endothelial dysfunction in the development of VSPI-associated LVSD. Furthermore, reduced resting myocardial blood flow is consistent with VSPI-induced microvascular constriction and consequent myocardial hypoperfusion. The normalisation of myocardial blood flow with adenosine-induced stress suggests that VSPI-induced microvascular vasoconstriction may be reversible and that vasodilator agents might be a potential strategy to prevent or treat the early cardiotoxic effects of VSPI. It remains to be established whether such microvascular changes remain reversible in patients exposed to VSPI therapies and indeed, whether any of the potential cardiotoxic effects or injury sustained or progressed in the longer term. Further prospective evaluation of larger groups of patients is necessary to provide robust data relating to the incidence and pathophysiology of VSPI-induced cardiotoxicity. This is required urgently to allow balanced decision-making before prescribing these effective anti-cancer therapies whilst minimising cardiovascular risk. Optimised cardiovascular surveillance strategies and mechanistically-targeted strategies to reduce VSPI-induced cardiovascular toxicity are both overdue. Funding This study was supported by NHS Greater Glasgow and Clyde Research and Development and by funds from the British Heart Foundation (RE/18/6/34217). Conflicts of interest: none declared. References 1Quaresma M, Coleman MP, Rachet B. 40-year trends in an index of survival for all cancers combined and survival adjusted for age and sex for each cancer in England and Wales, 1971-2011: a population-based study. Lancet 2015; 385: 1206– 1218. 2Zamorano JL, Lancellotti P, Muñoz DR, Aboyans V, Asteggiano R, Galderisi M, Habib G, Lenihan DJ, Lip GY, Lyon AR, Lopez Fernandez T, Mohty D, Piepoli MF, Tamargo J, Torbicki A, Suter TM. 2016 ESC Position Paper on cancer treatments and cardiovascular toxicity developed under the auspices of the ESC Committee for Practice Guidelines: the Task Force for Cancer Treatments and Cardiovascular Toxicity of the European Society of Cardiology (ESC). Eur J Heart Fail 2017; 19: 9– 42. 3Steeghs N, Gelderblom H, Roodt JO, Christensen O, Rajagopalan P, Hovens M, Putter H, Rabelink TJ, de Koning E. Hypertension and rarefaction during treatment with telatinib, a small molecule angiogenesis inhibitor. Clin Cancer Res 2008; 14: 3470– 3476. 4Narayan V, Keefe S, Haas N, Wang L, Puzanov I, Putt M, Catino A, Fang J, Agarwal N, Hyman D, Smith AM, Finkelman BS, Narayan HK, Ewer S, ElAmm C, Lenihan D, Ky B. Prospective evaluation of sunitinib-induced cardiotoxicity in patients with metastatic renal cell carcinoma. Clin Cancer Res 2017; 23: 3601– 3609. 5Papanastasiou G, Williams MC, Dweck MR, Mirsadraee S, Weir N, Fletcher A, Lucatelli C, Patel D, van Beek EJ, Newby DE, Semple SI. Multimodality quantitative assessments of myocardial perfusion using dynamic contrast enhanced magnetic resonance and 15 O-labeled water positron emission tomography imaging. IEEE Trans Radiat Plasma Med Sci 2018; 2: 259– 271. Citing Literature Volume22, Issue7July 2020Pages 1276-1277 FiguresReferencesRelatedInformation

Sodium (23Na) magnetic resonance imaging (MRI), especially brain applications are increasingly interesting since sodium MRI can provide additional information about tissue viability and vitality. In order to include sodium MRI in the clinical routine, a single RF setup is preferable which provides high sodium sensitivity and full proton performance in terms of signal-to-noise ratio (SNR) and parallel imaging performance. The aim of this work was to evaluate the feasibility of a double resonant receive (Rx) coil array for proton and sodium head MRI. The coil was designed to provide high sodium SNR and full proton performance comparable to commercial coils which are optimized for sodium MRI or for proton MRI, respectively. A measurement setup was built which comprised an 8-channel Rx degenerate Birdcage for sodium imaging and an 8-channel Rx array for proton imaging. The performance of the coil was evaluated against commercial sodium and proton coils using phantom and in-vivo measurements of two healthy volunteers.

The topology of a topological material can be encoded in its surface states. These surface states can only be removed by a bulk topological quantum phase transition into a trivial phase. Here we use photoemission spectroscopy to image the formation of protected surface states in a topological insulator as we chemically tune the system through a topological transition. Surprisingly, we discover an exotic spin-momentum locked, gapped surface state in the trivial phase that shares many important properties with the actual topological surface state in anticipation of the change of topology. Using a spin-resolved measurement, we show that apart from a surface bandgap these states develop spin textures similar to the topological surface states well before the transition. Our results offer a general paradigm for understanding how surface states in topological phases arise from a quantum phase transition and are suggestive for the future realization of Weyl arcs, condensed matter supersymmetry and other fascinating phenomena in the vicinity of a quantum criticality.

LiFePO4 is a battery cathode material with high safety standards due to its unique electronic structure. We performed systematic experimental and theoretical studies based on soft X-ray emission, absorption, and hard X-ray Raman spectroscopy of LixFePO4 nanoparticles and single crystals. The results clearly show a non-rigid electron-state reconfiguration of both the occupied and unoccupied Fe-3d and O-2p states during the (de)lithiation process. We focus on the energy configurations of the occupied states of LiFePO4 and the unoccupied states of FePO4, which are the critical states where electrons are removed and injected during the charge and discharge process, respectively. In LiFePO4, the soft X-ray emission spectroscopy shows that, due to the Coulomb repulsion effect, the occupied Fe-3d states with the minority spin sit close to the Fermi level. In FePO4, the soft X-ray absorption and hard X-ray Raman spectroscopy show that the unoccupied Fe-3d states again sit close to the Fermi level. These critical 3d electron state configurations are consistent with the calculations based on modified Becke and Johnson potentials GGA+U (MBJGGA+U) framework, which improves the overall lineshape prediction compared with the conventionally used GGA+U method. The combined experimental and theoretical studies show that the non-rigid electron state reshuffling guarantees the stability of oxygen during the redox reaction throughout the charge and discharge process of LiFePO4 electrodes, leading to the intrinsic safe performance of the electrodes.

A topological crystalline insulator (TCI) is a new phase of topological matter, which is predicted to exhibit distinct topological quantum phenomena, since space group symmetries replace the role of time-reversal symmetry in the much-studied Z$_2$ topological insulators. Utilizing high-resolution angle-resolved photoemission spectroscopy (ARPES), we reveal the momentum space nature of interconnectivity of the Fermi surface pockets leading to a saddle point singularity within the topological surface state alone in the TCI Pb$_{0.7}$Sn$_{0.3}$Se. Moreover, we show that the measured momentum-integrated density of states exhibits pronounced peaks at the saddle point energies, demonstrating the van Hove singularities (VHSs) in the topological surface states, whose surface chemical potential, as we show, can be tuned via surface chemical gating, providing access to the topological correlated physics on the surface. Our experimental data reveal a delicate relationship among lattice constant, band gap and spin-orbit coupling strength associated with the topological phase transition in Pb$_{1-x}$Sn$_{x}$Se. Furthermore, we explore the robustness of the TCI phase with VHS in Pb$_{1-x}$Sn$_{x}$Se, which shows a variety of distinct topological phase transitions driven by either thermal instability or broken crystalline symmetry, and thus revealing a rich topological phase diagram connectivity in Pb$_{1-x}$Sn$_{x}$Se for the first time.

Bismuth selenide (Bi2Se3) is a 3D topological insulator, its strong spin-orbit coupling resulting in the well-known topologically protected coexistence of gapless metallic surface states and semiconducting bulk states with a band gap, Eg ≃ 300 meV. A fundamental question of considerable importance is how the electronic properties of this material evolve under nanoscale confinement. We report on catalyst-free, high-quality single-crystalline Bi2Se3 with controlled lateral sizes and layer thicknesses that could be tailored down to a few nanometers and a few quintuple layers (QLs), respectively. Energy-resolved photoabsorption spectroscopy (1.5 eV < E(photon) < 6 eV) of these samples reveals a dramatic evolution of the photon absorption spectra as a function of size, transitioning from a featureless metal-like spectrum in the bulk (corresponding to a visually gray color), to one with a remarkably large band gap (Eg ≥ 2.5 eV) and a spectral shape that correspond to orange-red colorations in the smallest samples, similar to those seen in semiconductor nanostructures. We analyze this colorful transition using ab initio density functional theory and tight-binding calculations which corroborate our experimental findings and further suggest that while purely 2D sheets of few QL-thick Bi2Se3 do exhibit small band gaps that are consistent with previous ARPES results, the presently observed large gaps of a few electronvolts can only result from a combined effect of confinement in all three directions.

Understanding the spin-texture behaviour of boundary modes in ultrathin topological insulator films is critically essential for the design and fabrication of functional nanodevices. Here, by using spin-resolved photoemission spectroscopy with p-polarized light in topological insulator Bi2Se3 thin films, we report tunnelling-dependent evolution of spin configuration in topological insulator thin films across the metal-to-insulator transition. We report a systematic binding energy-and wavevector-dependent spin polarization for the topological surface electrons in the ultrathin gapped-Dirac-cone limit. The polarization decreases significantly with enhanced tunnelling realized systematically in thin insulating films, whereas magnitude of the polarization saturates to the bulk limit faster at larger wavevectors in thicker metallic films. We present a theoretical model that captures this delicate relationship between quantum tunnelling and Fermi surface spin polarization. Our high-resolution spin-based spectroscopic results suggest that the polarization current can be tuned to zero in thin insulating films forming the basis for a future spin-switch nanodevice.

Quantitative understanding of the relationship between quantum tunneling and Fermi surface spin polarization is key to device design using topological insulator surface states. By using spin-resolved photoemission spectroscopy with p-polarized light in topological insulator Bi2Se3 thin films across the metal-to-insulator transition, we observe that for a given film thickness, the spin polarization is large for momenta far from the center of the surface Brillouin zone. In addition, the polarization decreases significantly with enhanced tunneling realized systematically in thin insulating films, whereas magnitude of the polarization saturates to the bulk limit faster at larger wavevectors in thicker metallic films. Our theoretical model calculations capture this delicate relationship between quantum tunneling and Fermi surface spin polarization. Our results suggest that the polarization current can be tuned to zero in thin insulating films forming the basis for a future spin-switch nano-device.