Publications by authors named "Halperin B"

Article Synopsis
  • Josephson junctions allow for lossless electrical current flow in superconductors and are important for technologies like quantum bits, but understanding their supercurrent distribution has been challenging.
  • A new platform using a scanning magnetometer with nitrogen vacancy centers in diamond allows researchers to visualize supercurrent flow at the nanoscale, revealing competing ground states in zero-resistance conditions.
  • This research uncovers a new mechanism behind the Josephson diode effect and offers insights into unconventional superconductivity, which could improve quantum computing and energy-efficient technology.
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Electronic interferometers using the chiral, one-dimensional (1D) edge channels of the quantum Hall effect (QHE) can demonstrate a wealth of fundamental phenomena. The recent observation of phase jumps in a Fabry-Pérot (FP) interferometer revealed anyonic quasiparticle exchange statistics in the fractional QHE. When multiple integer edge channels are involved, FP interferometers have exhibited anomalous Aharonov-Bohm (AB) interference frequency doubling, suggesting putative pairing of electrons into quasiparticles.

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By directly altering microscopic interactions, pressure provides a powerful tuning knob for the exploration of condensed phases and geophysical phenomena. The megabar regime represents an interesting frontier, in which recent discoveries include high-temperature superconductors, as well as structural and valence phase transitions. However, at such high pressures, many conventional measurement techniques fail.

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Over the past decade, there have been considerable efforts to observe non-abelian quasiparticles in novel quantum materials and devices. These efforts are motivated by the goals of demonstrating quantum statistics of quasiparticles beyond those of fermions and bosons and of establishing the underlying science for the creation of topologically protected quantum bits. In this Review, we focus on efforts to create topological superconducting phases that host Majorana zero modes.

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Despite the efficacy, safety, and availability of COVID-19 vaccines, a lack of awareness and trust of vaccine safety research remains an important barrier to public health. The goal of this research was to design and test online meta-summaries-transparent, interactive summaries of the state of relevant studies-to improve people's awareness and opinion of vaccine safety research. We used insights from a set of co-design interviews (n = 22) to develop meta-summaries to highlight metascientific information about vaccine safety research.

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In fermionic systems, superconductivity and superfluidity occur through the condensation of fermion pairs. The nature of this condensate can be tuned by varying the pairing strength, which is challenging in electronic systems. We studied graphene double layers separated by an atomically thin insulator.

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We introduce a new variational wave function for a quantum Hall bilayer at total filling ν_{T}=1, which is based on s-wave BCS pairing between electron composite fermions in one layer and hole composite fermions in the other. In addition, we reexamine a trial wave function based on p-wave BCS pairing between electron composite fermions in both layers. We compute the overlap of the optimized trial functions with the ground state from exact diagonalization calculations of up to 14 electrons in a spherical geometry, and we find excellent agreement over the entire range of values of the ratio between the layer separation and the magnetic length.

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Background: The STOP AF First trial recently demonstrated that initial treatment with cryoballoon ablation (CBA) is safe and superior to antiarrhythmic drug (AAD) therapy for preventing atrial arrhythmia recurrence in patients with symptomatic atrial fibrillation (AF).

Objective: The purpose of this study was to evaluate the change in quality of life (QoL) and symptoms after first-line CBA vs AAD therapy.

Methods: Patients with symptomatic AF not previously receiving rhythm control therapy were randomized to AAD (class I or III) or CBA (Arctic Front Advance, Medtronic, Mounds View, MN).

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Quasiparticles with fractional charge and fractional statistics are key features of the fractional quantum Hall effect. We discuss in detail the definitions of fractional charge and statistics and the ways in which these properties may be observed. In addition to theoretical foundations, we review the present status of the experiments in the area.

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Background: In patients with symptomatic paroxysmal atrial fibrillation that has not responded to medication, catheter ablation is more effective than antiarrhythmic drug therapy for maintaining sinus rhythm. However, the safety and efficacy of cryoballoon ablation as initial first-line therapy have not been established.

Methods: We performed a multicenter trial in which patients 18 to 80 years of age who had paroxysmal atrial fibrillation for which they had not previously received rhythm-control therapy were randomly assigned (1:1) to receive treatment with antiarrhythmic drugs (class I or III agents) or pulmonary vein isolation with a cryoballoon.

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Topological superconductors can support localized Majorana states at their boundaries. These quasi-particle excitations obey non-Abelian statistics that can be used to encode and manipulate quantum information in a topologically protected manner. Although signatures of Majorana bound states have been observed in one-dimensional systems, there is an ongoing effort to find alternative platforms that do not require fine-tuning of parameters and can be easily scaled to large numbers of states.

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Spin waves are collective excitations of magnetic systems. An attractive setting for studying long-lived spin-wave physics is the quantum Hall (QH) ferromagnet, which forms spontaneously in clean two-dimensional electron systems at low temperature and in a perpendicular magnetic field. We used out-of-equilibrium occupation of QH edge channels in graphene to excite and detect spin waves in magnetically ordered QH states.

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Background: Immunization of pregnant women with tetanus-diphtheria-acellular pertussis vaccine (Tdap) provides protection against pertussis to the newborn infant.

Methods: In a randomized, controlled, observer-blind, multicenter clinical trial, we measured the safety and immunogenicity of Tdap during pregnancy and the effect on the infant's immune response to primary vaccination at 2, 4, and 6 months and booster vaccination at 12 months of age. A total of 273 women received either Tdap or tetanus-diphtheria (Td) vaccine in the third trimester and provided information for the safety analysis and samples for the immunogenicity analyses; 261 infants provided serum for the immunogenicity analyses.

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Confined to a two-dimensional plane, electrons in a strong magnetic field travel along the edge in one-dimensional quantum Hall channels that are protected against backscattering. These channels can be used as solid-state analogs of monochromatic beams of light, providing a unique platform for studying electron interference. Electron interferometry is regarded as one of the most promising routes for studying fractional and non-Abelian statistics and quantum entanglement via two-particle interference.

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In the half filled zero-energy Landau level of bilayer graphene, competing phases with spontaneously broken symmetries and an intriguing quantum critical behavior have been predicted. Here we investigate signatures of these broken-symmetry phases in thermal transport measurements. To this end, we calculate the spectrum of spin and valley waves in the ν=0 quantum Hall state of bilayer graphene.

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Objectives: During an outbreak of invasive meningococcal B disease on a university campus, we explored the knowledge, attitudes, beliefs, and behaviors of members of the university community in relation to the disease, the vaccine, and the vaccination program.

Design: All students, faculty and staff were invited by email to participate in a 71-item online survey, which was administered after completion of the mass clinics for the first and second doses of a meningococcal B vaccination program.

Results: A total of 404 individuals responded to the survey; 75.

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Background: This research explored the role of attitudes in acceptance of organizational change initiatives.

Methods: A survey assessed factors associated with health care provider (HCP) likelihood to accept seasonal influenza vaccine policy changes. We evaluated the impact of knowledge and individual attitudes on this outcome measure.

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Background: Annual immunization is the most effective way to prevent influenza and its associated complications. However, optimal immunization rates are not being met in Nova Scotia, Canada. Additional providers, such as pharmacists, may improve access and convenience to receive vaccines.

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An outbreak of Neisseria meningitidis serotype B infection occurred at a small residential university; public health announced an organizational vaccination program with the 4-component Meningococcal B (4CMenB) vaccine (Bexsero(TM), Novartis/GlaxoSmithKline Inc.) several days later. Since there were limited published data on reactogenicity of 4CMenB in persons over 17years of age, this study sought to conduct rapid surveillance of health events in vaccinees and controls using an online survey.

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Strong electron interactions can lead to a variety of broken-symmetry phases in monolayer graphene. In the quantum Hall regime, the interaction effect are enhanced by the formation of highly degenerate Landau levels, catalyzing the emergence of such phases. Recent magnetotransport studies show evidence that the ν=0 quantum Hall state of graphene is in an insulating canted antiferromagnetic phase with the Néel vector lying within the graphene plane.

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Immunization with pertussis vaccine during pregnancy is recommended in a number of countries to prevent newborn deaths from whooping cough. In some jurisdictions, vaccine uptake during pregnancy is low. We undertook a survey of the knowledge, attitudes, beliefs, and behaviors of pregnant women who had been approached to participate in a randomized, controlled trial of tetanus-diphtheria-acellular pertussis (Tdap) vaccine during pregnancy.

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Fermions and bosons are fundamental realizations of exchange statistics, which governs the probability for two particles being close to each other spatially. Anyons in the fractional quantum Hall effect are an example for exchange statistics intermediate between bosons and fermions. We analyze a mesoscopic setup in which two dilute beams of anyons collide with each other, and relate the correlations of current fluctuations to the probability of particles excluding each other spatially.

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Immunization coverage in Canada has continued to fall below national goals. The addition of pharmacists as immunizers may increase immunization coverage. This study aimed to compare estimated influenza vaccine coverage before and after pharmacists began administering publicly funded influenza immunizations in Nova Scotia, Canada.

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Vaccine coverage among adults for recommended vaccines is generally low. In Canada and the US, pharmacists are increasingly becoming involved in the administration of vaccines to adults. This study measured the knowledge, attitudes, beliefs, and behaviors of Canadian adults and health care providers regarding pharmacists as immunizers.

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