Publications


Magnetic field-induced pair density wave state in the cuprate vortex halo.

Science (New York, N.Y.) 364 (2019) 976-980

SD Edkins, A Kostin, K Fujita, AP Mackenzie, H Eisaki, S Uchida, S Sachdev, MJ Lawler, E-A Kim, JC Séamus Davis, MH Hamidian

High magnetic fields suppress cuprate superconductivity to reveal an unusual density wave (DW) state coexisting with unexplained quantum oscillations. Although routinely labeled a charge density wave (CDW), this DW state could actually be an electron-pair density wave (PDW). To search for evidence of a field-induced PDW, we visualized modulations in the density of electronic states N(r) within the halo surrounding Bi2Sr2CaCu2O8 vortex cores. We detected numerous phenomena predicted for a field-induced PDW, including two sets of particle-hole symmetric N(r) modulations with wave vectors QP and 2QP , with the latter decaying twice as rapidly from the core as the former. These data imply that the primary field-induced state in underdoped superconducting cuprates is a PDW, with approximately eight CuO2 unit-cell periodicity and coexisting with its secondary CDWs.


Magnetic structure and spin-flop transition in the A -site columnar-ordered quadruple perovskite TmMn3O6

Physical Review B American Physical Society (APS) 99 (2019) 104424

AM Vibhakar, DD Khalyavin, P Manuel, L Zhang, K Yamaura, PG Radaelli, AA Belik, RD Johnson


Magnetic profile of proximity-coupled (Dy,Bi)(2)Te-3/(Cr,Sb)(2)Te(3 )topological insulator heterostructures

PHYSICAL REVIEW B 100 (2019) ARTN 054402

LB Duffy, N-J Steinke, DM Burn, A Frisk, L Lari, B Kuerbanjiang, VK Lazarov, G van der Laan, S Langridge, T Hesjedal


India and the United Kingdom-What big data health research can do for a country.

Learning health systems 3 (2019) e10074-

S Bandopadhyay, GVS Murthy, D Prabhakaran, P Taylor, A Banerjee

Introduction:Big data and growth in telecommunications have increased the enormous promise of an informatics approach to health care. India and the United Kingdom are two countries facing these challenges of implementing learning health systems and big data health research. Analysis:At present, these opportunities are more likely to be exploited in the private sector or in public-private partnerships (eg, Public Health Foundation of India [PHFI]) than public sector ventures alone. In both India and the United Kingdom, the importance of health informatics (HIs), a relatively new discipline, is being recognised and there are national initiatives in academic and health sectors to fill gaps in big data health research. The challenges are in many ways greater in India but outweighed by three potential benefits in health-related scientific research: (a) increased productivity; (b) a learning health system with better use of data and better health outcomes; and (c) to fill workforce gaps in both research and practice. Conclusions:Despite several system-level obstacles, in India, big data research in health care can improve the status quo, whether in terms of patient outcomes or scientific discovery. Collaboration between India and the United Kingdom in HI can result in mutual benefits to academic and health care delivery organisations in both countries and can serve as examples to other countries embracing the promises and the pitfalls of health care research in the digital era.


Enhancement of intrinsic magnetic damping in defect-free epitaxial Fe3O4 thin films

APPLIED PHYSICS LETTERS 114 (2019) ARTN 192406

X Lu, LJ Atkinson, B Kuerbanjiang, B Liu, G Li, Y Wang, J Wang, X Ruan, J Wu, RFL Evans, VK Lazarov, RW Chantrell, Y Xu


Electromagnon excitation in cupric oxide measured by Fabry-Pérot enhanced terahertz Mueller matrix ellipsometry.

Scientific reports 9 (2019) 1353-

S Knight, D Prabhakaran, C Binek, M Schubert

Here we present the use of Fabry-Pérot enhanced terahertz (THz) Mueller matrix ellipsometry to measure an electromagnon excitation in monoclinic cupric oxide (CuO). As a magnetically induced ferroelectric multiferroic, CuO exhibits coupling between electric and magnetic order. This gives rise to special quasiparticle excitations at THz frequencies called electromagnons. In order to measure the electromagnons in CuO, we exploit single-crystal CuO as a THz Fabry-Pérot cavity to resonantly enhance the excitation's signature. This enhancement technique enables the complex index of refraction to be extracted. We observe a peak in the absorption coefficient near 0.705 THz and 215 K, which corresponds to the electromagnon excitation. This absorption peak is observed along only one major polarizability axis in the monoclinic a-c plane. We show the excitation can be represented using the Lorentz oscillator model, and discuss how these Lorentz parameters evolve with temperature. Our findings are in excellent agreement with previous characterizations by THz time-domain spectroscopy (THz-TDS), which demonstrates the validity of this enhancement technique.


Strain Engineering a Multiferroic Monodomain in Thin-Film BiFeO3

PHYSICAL REVIEW APPLIED 11 (2019) ARTN 024035

NW Price, AM Vibhakar, RD Johnson, J Schad, W Saenrang, A Bombardi, FP Chmiel, CB Eom, PG Radaelli


Response by Prabhakaran et al to Letter Regarding Article, "Effectiveness of an mHealth-Based Electronic Decision Support System for Integrated Management of Chronic Conditions in Primary Care: The mWellcare Cluster-Randomized Controlled Trial".

Circulation 139 (2019) e1039-

D Prabhakaran, D Jha, VS Ajay, A Roy, P Perel


Machine learning in electronic-quantum-matter imaging experiments.

Nature 570 (2019) 484-490

Y Zhang, A Mesaros, K Fujita, SD Edkins, MH Hamidian, K Ch'ng, H Eisaki, S Uchida, JCS Davis, E Khatami, E-A Kim

For centuries, the scientific discovery process has been based on systematic human observation and analysis of natural phenomena1. Today, however, automated instrumentation and large-scale data acquisition are generating datasets of such large volume and complexity as to defy conventional scientific methodology. Radically different scientific approaches are needed, and machine learning (ML) shows great promise for research fields such as materials science2-5. Given the success of ML in the analysis of synthetic data representing electronic quantum matter (EQM)6-16, the next challenge is to apply this approach to experimental data-for example, to the arrays of complex electronic-structure images17 obtained from atomic-scale visualization of EQM. Here we report the development and training of a suite of artificial neural networks (ANNs) designed to recognize different types of order hidden in such EQM image arrays. These ANNs are used to analyse an archive of experimentally derived EQM image arrays from carrier-doped copper oxide Mott insulators. In these noisy and complex data, the ANNs discover the existence of a lattice-commensurate, four-unit-cell periodic, translational-symmetry-breaking EQM state. Further, the ANNs determine that this state is unidirectional, revealing a coincident nematic EQM state. Strong-coupling theories of electronic liquid crystals18,19 are consistent with these observations.


Tackling the Burden of Cardiovascular Diseases in India.

Circulation. Cardiovascular quality and outcomes 12 (2019) e005195-

AA Abdul-Aziz, P Desikan, D Prabhakaran, LF Schroeder


Structural and Optical Properties of Cs2AgBiBr6 Double Perovskite

ACS ENERGY LETTERS 4 (2019) 299-305

L Schade, AD Wright, RD Johnson, M Dollmann, B Wenger, PK Nayak, D Prabhakaran, LM Herz, R Nicholas, HJ Snaith, PG Radaelli


Cr2Te3 Thin Films for Integration in Magnetic Topological Insulator Heterostructures.

Scientific reports 9 (2019) 10793-

DM Burn, LB Duffy, R Fujita, SL Zhang, AI Figueroa, J Herrero-Martin, G van der Laan, T Hesjedal

Chromium telluride compounds are promising ferromagnets for proximity coupling to magnetic topological insulators (MTIs) of the Cr-doped (Bi,Sb)2(Se,Te)3 class of materials as they share the same elements, thus simplifying thin film growth, as well as due to their compatible crystal structure. Recently, it has been demonstrated that high quality (001)-oriented Cr2Te3 thin films with perpendicular magnetic anisotropy can be grown on c-plane sapphire substrate. Here, we present a magnetic and soft x-ray absorption spectroscopy study of the chemical and magnetic properties of Cr2Te3 thin films. X-ray magnetic circular dichroism (XMCD) measured at the Cr L2,3 edges gives information about the local electronic and magnetic structure of the Cr ions. We further demonstrate the overgrowth of Cr2Te3 (001) thin films by high-quality Cr-doped Sb2Te3 films. The magnetic properties of the layers have been characterized and our results provide a starting point for refining the physical models of the complex magnetic ordering in Cr2Te3 thin films, and their integration into advanced MTI heterostructures for quantum device applications.


Implementation and acceptability of a heart attack quality improvement intervention in India: a mixed methods analysis of the ACS QUIK trial.

Implementation science : IS 14 (2019) 12-

K Singh, R Devarajan, PP Mohanan, AS Baldridge, D Kondal, DE Victorson, KN Karmali, L Zhao, DM Lloyd-Jones, D Prabhakaran, S Goenka, MD Huffman, ACS QUIK Investigators

BACKGROUND:The ACS QUIK trial showed that a multicomponent quality improvement toolkit intervention resulted in improvements in processes of care for patients with acute myocardial infarction in Kerala but did not improve clinical outcomes in the context of background improvements in care. We describe the development of the ACS QUIK intervention and evaluate its implementation, acceptability, and sustainability. METHODS:We performed a mixed methods process evaluation alongside a cluster randomized, stepped-wedge trial in Kerala, India. The ACS QUIK intervention aimed to reduce the rate of major adverse cardiovascular events at 30 days compared with usual care across 63 hospitals (n = 21,374 patients). The ACS QUIK toolkit intervention, consisting of audit and feedback report, admission and discharge checklists, patient education materials, and guidelines for the development of code and rapid response teams, was developed based on formative qualitative research in Kerala and from systematic reviews. After four or more months of the center's participation in the toolkit intervention phase of the trial, an online survey and physician interviews were administered. Physician interviews focused on evaluating the implementation and acceptability of the toolkit intervention. A framework analysis of transcripts incorporated context and intervening mechanisms. RESULTS:Among 63 participating hospitals, 22 physicians (35%) completed online surveys. Of these, 17 (77%) respondents reported that their hospital had a cardiovascular quality improvement team, 18 (82%) respondents reported having read an audit report, admission checklist, or discharge checklist, and 19 (86%) respondents reported using patient education materials. Among the 28 interviewees (44%), facilitators of toolkit intervention implementation were physicians' support and leadership, hospital administrators' support, ease-of-use of checklists and patient education materials, and availability of training opportunities for staff. Barriers that influenced the implementation or acceptability of the toolkit intervention for physicians included time and staff constraints, Internet access, patient volume, and inadequate understanding of the quality improvement toolkit intervention. CONCLUSIONS:Implementation and acceptability of the ACS QUIK toolkit intervention were enhanced by hospital-level management support, physician and team support, and usefulness of checklists and patient education materials. Wider and longer-term use of the toolkit intervention and its expansion to potentially other cardiovascular conditions or other locations where the quality of care is not as high as in the ACS QUIK trial may be useful for improving acute cardiovascular care in Kerala and beyond. TRIAL REGISTRATION:NCT02256657.


Spin-charge-lattice coupling in quasi-one-dimensional Ising spin chain CoNb2O6.

Journal of physics. Condensed matter : an Institute of Physics journal 31 (2019) 195802-

M Nandi, D Prabhakaran, P Mandal

Magnetization, magnetostriction and dielectric constant measurements are performed on single crystals of quasi-one-dimensional Ising spin chain CoNb2O6 at temperatures below and above the antiferromagnetic phase transition. Field-induced magnetic transitions are clearly reflected in magnetodielectric and magnetostriction data. Sharp anomalies are observed around the critical fields of antiferromagnetic to ferrimagnetic and ferrimagnetic to saturated-paramagnetic transition in both magnetodielectric and magnetostriction experiments. Detailed analysis of temperature and field dependence of dielectric constant and magnetostriction suggests that spins are coupled with lattice as well as charges in CoNb2O6. Below the antiferromagnetic transition temperature, the overall resemblance in anomalies, observed in various physical parameters such as magnetization, dielectric constant, magnetostriction and magnetic entropy change gives a deeper insight about the influence of spin configuration on these parameters in CoNb2O6.


Hospital-based quality improvement interventions for patients with heart failure: a systematic review.

Heart (British Cardiac Society) 105 (2019) 431-438

A Agarwal, E Bahiru, SGK Yoo, MA Berendsen, S Harikrishnan, AF Hernandez, D Prabhakaran, MD Huffman

OBJECTIVE:To estimate the direction and magnitude of effect and quality of evidence for hospital-based heart failure (HF) quality improvement interventions on process of care measures and clinical outcomes among patients with acute HF. REVIEW METHODS:We performed a structured search to identify relevant randomised trials evaluating the effect of in-hospital quality improvement interventions for patients hospitalised with HF through February 2017. Studies were independently reviewed in duplicate for key characteristics, outcomes were summarised and a qualitative synthesis was performed due to substantial heterogeneity. RESULTS:From 3615 records, 14 randomised controlled trials were identified for inclusion with multifaceted interventions. There was a trend towards higher in-hospital use of ACE inhibitors (ACE-I; 57.9%vs40.0%) and beta-blockers (BBs; 46.7%vs10.2%) in the intervention than the comparator in one trial (n=429 participants). Five trials (n=78 727 participants) demonstrated no effect of the intervention on use of ACE-I or angiotensin receptor blocker at discharge. Three trials (n=89 660 participants) reported no effect on use of BB at discharge. Two trials (n=419 participants) demonstrated a trend towards lower hospital readmission up to 90 days after discharge. There was no consistent effect of the quality improvement intervention on 30-day all-cause mortality, hospital length of stay and patient-level health-related quality of life. CONCLUSIONS:Randomised trials of hospital-based HF quality improvement interventions do not show a consistent effect on most process of care measures and clinical outcomes. The overall quality of evidence for the prespecified primary and key secondary outcomes was very low to moderate, suggesting that future research will likely influence these estimates. TRIAL REGISTRATION NUMBER:CRD42016049545.


Selective probing of magnetic order on Tb and Ir sites in stuffed Tb2Ir2O7  using resonant x-ray scattering.

Journal of physics. Condensed matter : an Institute of Physics journal 31 (2019) 344001-

C Donnerer, MC Rahn, E Schierle, RS Perry, LSI Veiga, G Nisbet, SP Collins, D Prabhakaran, AT Boothroyd, DF McMorrow

We study the magnetic structure of the 'stuffed' (Tb-rich) pyrochlore iridate Tb2+x Ir2-x O7-y  (x ∼ 0.18), using resonant elastic x-ray scattering (REXS). In order to disentangle contributions from Tb and Ir magnetic sublattices, experiments were performed at the Ir L 3 and Tb M 5 edges, which provide selective sensitivity to Ir 5d and Tb 4f  magnetic moments, respectively. At the Ir L 3 edge, we found the onset of long-range [Formula: see text] magnetic order below [Formula: see text] K, consistent with the expected signal of all-in all-out (AIAO) magnetic order. Using a single-ion model to calculate REXS cross-sections, we estimate an ordered magnetic moment of [Formula: see text] at 5 K. At the Tb M 5 edge, long-range [Formula: see text] magnetic order appeared below  ∼[Formula: see text] K, also consistent with an AIAO magnetic structure on the Tb site. Additional insight into the magnetism of the Tb sublattice is gleaned from measurements at the M 5 edge in applied magnetic fields up to 6 T, which is found to completely suppress the Tb AIAO magnetic order. In zero applied field, the observed gradual onset of the Tb sublattice magnetisation with temperature suggests that it is induced by the magnetic order on the Ir site. The persistence of AIAO magnetic order, despite the greatly reduced ordering temperature and moment size compared to stoichiometric Tb2Ir2O7, for which [Formula: see text] K and [Formula: see text], indicates that stuffing could be a viable means of tuning the strength of electronic correlations, thereby potentially offering a new strategy to achieve topologically non-trivial band crossings in pyrochlore iridates.


May Measurement Month 2018: a pragmatic global screening campaign to raise awareness of blood pressure by the International Society of Hypertension.

European heart journal 40 (2019) 2006-2017

T Beaney, LM Burrell, RR Castillo, FJ Charchar, S Cro, A Damasceno, R Kruger, PM Nilsson, D Prabhakaran, AJ Ramirez, MP Schlaich, AE Schutte, M Tomaszewski, R Touyz, J-G Wang, MA Weber, NR Poulter, MMM Investigators

AIMS:Raised blood pressure (BP) is the biggest contributor to mortality and disease burden worldwide and fewer than half of those with hypertension are aware of it. May Measurement Month (MMM) is a global campaign set up in 2017, to raise awareness of high BP and as a pragmatic solution to a lack of formal screening worldwide. The 2018 campaign was expanded, aiming to include more participants and countries. METHODS AND RESULTS:Eighty-nine countries participated in MMM 2018. Volunteers (≥18 years) were recruited through opportunistic sampling at a variety of screening sites. Each participant had three BP measurements and completed a questionnaire on demographic, lifestyle, and environmental factors. Hypertension was defined as a systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg, or taking antihypertensive medication. In total, 74.9% of screenees provided three BP readings. Multiple imputation using chained equations was used to impute missing readings. 1 504 963 individuals (mean age 45.3 years; 52.4% female) were screened. After multiple imputation, 502 079 (33.4%) individuals had hypertension, of whom 59.5% were aware of their diagnosis and 55.3% were taking antihypertensive medication. Of those on medication, 60.0% were controlled and of all hypertensives, 33.2% were controlled. We detected 224 285 individuals with untreated hypertension and 111 214 individuals with inadequately treated (systolic BP ≥ 140 mmHg or diastolic BP ≥ 90 mmHg) hypertension. CONCLUSION:May Measurement Month expanded significantly compared with 2017, including more participants in more countries. The campaign identified over 335 000 adults with untreated or inadequately treated hypertension. In the absence of systematic screening programmes, MMM was effective at raising awareness at least among these individuals at risk.


Phase transitions, broken symmetry and the renormalization group

in The Routledge Handbook of Emergence, (2019) 237-247

SJ Blundell

© 2019 selection and editorial matter, Sophie Gibb, Robin Findlay Hendry, and Tom Lancaster. All rights reserved. The renormalization group should probably be called the renormalization semigroup, but sometimes, contradictory terminology sticks. The renormalization group procedure provides important insights because it shows quantitatively how fine-scale structure is progressively ignored and the physics of critical phenomena depend on these larger-scale, what students might call "structural", features of the theory. The renormalization group breaks big problems down into small ones. Broken symmetry can be seen as a well-studied paradigm of emergent behaviour in the physical world. By breaking symmetry, these phases forfeit the status of being a "stationary state" of the sort beloved of elementary quantum mechanics treatments. Phase transitions are sharp and there is a clear delineation between the ordered and disordered states. The set of symmetry-breaking phase transitions includes as members those between the ferromagnetic and paramagnetic states and those between the superconducting and normal metal states of certain materials.


Temperature dependence of the ferromagnetic response in CrxSb2-xTe3 topological insulator thin films investigated using terahertz spectroscopy and magneto-transport

TERAHERTZ, RF, MILLIMETER, AND SUBMILLIMETER-WAVE TECHNOLOGY AND APPLICATIONS XII 10917 (2019)

VS Kamboj, A Singh, L Jakob, LB Duffy, N Idros, SP Senanayak, A Ionescu, HE Beere, CHW Barnes, T Hesjedal, DA Ritchie


Expanding the Lorentz Concept in Magnetism

New Journal of Physics IOP Publishing (2019)

G Bowden, G van der Laan, T HESJEDAL, RJ Hicken

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