Coexistence of Superconductivity and Antiferromagnetism in Topological Magnet MnBi2Te4 Films.

The interface of two materials can harbor unexpected emergent phenomena. One example is interface-induced superconductivity. In this work, we employ molecular beam epitaxy to grow a series of heterostructures formed by stacking together two nonsuperconducting antiferromagnetic materials, an intrinsic antiferromagnetic topological insulator MnBi2Te4 and an antiferromagnetic iron chalcogenide FeTe. Our electrical transport measurements reveal interface-induced superconductivity in these heterostructures. By performing scanning tunneling microscopy and spectroscopy measurements, we observe a proximity-induced superconducting gap on the top surface of the MnBi2Te4 layer, confirming the coexistence of superconductivity and antiferromagnetism in the MnBi2Te4 layer. Our findings will advance the fundamental inquiries into the topological superconducting phase in hybrid devices and provide a promising platform for the exploration of chiral Majorana physics in MnBi2Te4-based heterostructures.

Interface-induced superconductivity in magnetic topological insulators.

The interface between two different materials can show unexpected quantum phenomena. In this study, we used molecular beam epitaxy to synthesize heterostructures formed by stacking together two magnetic materials, a ferromagnetic topological insulator (TI) and an antiferromagnetic iron chalcogenide (FeTe). We observed emergent interface-induced superconductivity in these heterostructures and demonstrated the co-occurrence of superconductivity, ferromagnetism, and topological band structure in the magnetic TI layer-the three essential ingredients of chiral topological superconductivity (TSC). The unusual coexistence of ferromagnetism and superconductivity is accompanied by a high upper critical magnetic field that exceeds the Pauli paramagnetic limit for conventional superconductors at low temperatures. These magnetic TI/FeTe heterostructures with robust superconductivity and atomically sharp interfaces provide an ideal wafer-scale platform for the exploration of chiral TSC and Majorana physics.

Dirac-fermion-assisted interfacial superconductivity in epitaxial topological-insulator/iron-chalcogenide heterostructures.

Over the last decade, the possibility of realizing topological superconductivity (TSC) has generated much excitement. TSC can be created in electronic systems where the topological and superconducting orders coexist, motivating the continued exploration of candidate material platforms to this end. Here, we use molecular beam epitaxy (MBE) to synthesize heterostructures that host emergent interfacial superconductivity when a non-superconducting antiferromagnet (FeTe) is interfaced with a topological insulator (TI) (Bi, Sb)2Te3. By performing in-vacuo angle-resolved photoemission spectroscopy (ARPES) and ex-situ electrical transport measurements, we find that the superconducting transition temperature and the upper critical magnetic field are suppressed when the chemical potential approaches the Dirac point. We provide evidence to show that the observed interfacial superconductivity and its chemical potential dependence is the result of the competition between the Ruderman-Kittel-Kasuya-Yosida-type ferromagnetic coupling mediated by Dirac surface states and antiferromagnetic exchange couplings that generate the bicollinear antiferromagnetic order in the FeTe layer.

Control of electronic topology in a strongly correlated electron system.

It is becoming increasingly clear that breakthrough in quantum applications necessitates materials innovation. In high demand are conductors with robust topological states that can be manipulated at will. This is what we demonstrate in the present work. We discover that the pronounced topological response of a strongly correlated "Weyl-Kondo" semimetal can be genuinely manipulated-and ultimately fully suppressed-by magnetic fields. We understand this behavior as a Zeeman-driven motion of Weyl nodes in momentum space, up to the point where the nodes meet and annihilate in a topological quantum phase transition. The topologically trivial but correlated background remains unaffected across this transition, as is shown by our investigations up to much larger fields. Our work lays the ground for systematic explorations of electronic topology, and boosts the prospect for topological quantum devices.

Evidence for a delocalization quantum phase transition without symmetry breaking in CeCoIn5.

The study of quantum phase transitions that are not clearly associated with broken symmetry is a major effort in condensed matter physics, particularly in regard to the problem of high-temperature superconductivity, for which such transitions are thought to underlie the mechanism of superconductivity itself. Here we argue that the putative quantum critical point in the prototypical unconventional superconductor CeCoIn5 is characterized by the delocalization of electrons in a transition that connects two Fermi surfaces of different volumes, with no apparent broken symmetry. Drawing on established theory of f-electron metals, we discuss an interpretation for such a transition that involves the fractionalization of spin and charge, a model that effectively describes the anomalous transport behavior we measured for the Hall effect.

Spatial control of heavy-fermion superconductivity in CeIrIn5.

Although crystals of strongly correlated metals exhibit a diverse set of electronic ground states, few approaches exist for spatially modulating their properties. In this study, we demonstrate disorder-free control, on the micrometer scale, over the superconducting state in samples of the heavy-fermion superconductor CeIrIn5 We pattern crystals by focused ion beam milling to tailor the boundary conditions for the elastic deformation upon thermal contraction during cooling. The resulting nonuniform strain fields induce complex patterns of superconductivity, owing to the strong dependence of the transition temperature on the strength and direction of strain. These results showcase a generic approach to manipulating electronic order on micrometer length scales in strongly correlated matter without compromising the cleanliness, stoichiometry, or mean free path.

Baseline Dietary Intake of Individuals with Spinal Cord Injury Who Are Overweight or Obese.

BACKGROUND: Individuals with spinal cord injury (SCI) experience significant secondary health conditions including excess adiposity. Dietary guidelines for individuals with chronic SCI do not exist. OBJECTIVE: To describe baseline dietary intake and quality based on conformance with dietary recommendations in participants enrolled in GoHealthySCI, a weight loss intervention for individuals with SCI, which promotes lifestyle change. DESIGN: Cross-sectional analyses were conducted on data collected from April through August 2017 in a randomized pilot study. PARTICIPANTS: Thirty-seven participants enrolled in the study in Houston, TX. All participants were at least 1 year post injury with a self-reported body mass index (calculated as kg/m2) ≥23. The racially/ethnically diverse sample was predominantly male (n=23), average age was 41.8±13.5 years, and average number of years since injury was 18.1±14.9. Participants varied in terms of level of injury; 19 participants identified as having tetraplegia and 19 identified as having paraplegia. MAIN OUTCOME MEASURES: The Automated Self-Administered 24-Hour Recall dietary assessment was used to obtain baseline dietary intake data. Participants reported food intake on 3 nonconsecutive days. STATISTICAL ANALYSIS: Descriptive statistics were conducted for the primary research objectives. Mean macronutrient and micronutrient intake and Healthy Eating Index-2015 total and component scores are described. RESULTS: Average daily energy intake was 1618±434 kcal. Daily intakes of whole fruits (0.6±0.7 cups), vegetables (1.6±0.9 cups), and whole grains (15%) of total grains were lower than recommendations from the 2015-2020 Dietary Guidelines for Americans. Average daily fiber (15.0g±6.0) met the Academy of Nutrition and Dietetics Evidence Analysis Library minimum target range for individuals with SCI. All percentages of calories from macronutrients were within the acceptable macronutrient distribution ranges: total fat (34.3%±6.2%), protein (16.7%±4.2%), and carbohydrate (49.3%±8.4%). Mean Healthy Eating Index-2015 score was 54.4. CONCLUSIONS: This study provides a description of dietary intake by individuals with SCI who are overweight or obese. Although macronutrients are within the acceptable distribution range, calories from fat are at the high end and those from protein are at the low end of those ranges. In addition, on average, individuals reported inadequate intake of fruits, vegetables, whole grains, fiber, seafood and plant protein, and healthy fats and excess intake of added sugars and saturated fat. Results provide preliminary evidence of dietary inadequacies and suggest that larger studies examining dietary intake are warranted.