High-Field Superconductivity at an Electronic Topological Transition in URhGe

The emergence of superconductivity at high magnetic fields in URhGe is regarded as a paradigm for new state formation approaching a quantum critical point. Until now, a divergence of the quasiparticle mass at the metamagnetic transition was considered essential for superconductivity to survive at magnetic fields above 30 tesla. Here we report the observation of quantum oscillations in URhGe revealing a tiny pocket of heavy quasiparticles that shrinks continuously with increasing magnetic field, and finally disappears at a topological Fermi surface transition close to or at the metamagnetic field. The quasiparticle mass decreases and remains finite, implying that the Fermi velocity vanishes due to the collapse of the Fermi wavevector. This offers a novel explanation for the re-emergence of superconductivity at extreme magnetic fields and makes URhGe the first proven example of a material where magnetic field-tuning of the Fermi surface, rather than quantum criticality alone, governs quantum phase formation.Comment: A revised version has been accepted for publication in Nature Physic

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency–Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research

Observation of the magnetic field dependence of the cyclotron mass in the Kondo lattice CeB6.

Low-temperature, high-field deHaas van Alphen measurements are presented which show that the conduction-electron mass in the Kondo lattice CeB6 decreases strongly with field. This field dependence is consistent with recent specific-heat results. The geometry of the Fermi surface does not depend on field. Thus we observe a reduction in the many-body enhancement of the electronic density of states at the Fermi energy which is described by a change of the itinerant-electron mass alone; the number of particles and the occupation of states in k space remain unchanged. We argue that CeB6 represents a different limit of heavy-fermion behavior as compared to UPt3. © 1987 The American Physical Society

Suppression of the mass enhancement in ceb6 in high magnetic fields

The effective mass of the itinerant electrons in the Kondo lattice system CeB6 is found to be strongly field dependent. Measurements of the de Haas-van Alphen effect at temperatures down to 60 mK in steady magnetic fields up to 22 T show a change of more than 100% in the cyclotron effective mass, decreasing with increasing field. The origin of the effect is not known but it is noted that a field of about 10 T corresponds to the energy scales in the system. © 1987 The Japan Society of Applied Physics

Magnetic field dependence of the cyclotron effective mass in the Kondo lattice CeB6

We report the first observation of a field-dependent mass in a hybridizing f-electron system. CeB6 is an ordered moment heavy fermion system with an electronic specific heat coefficient γ of order 225-300 mJ/mole K2. Using the de Haas-van Alphen effect at temperatures as low as 60 mK in steady magnetic fields as large as 22 T, we observe a cyclotron orbit of frequency 8680 T for fields along the [100] direction. The mass of this orbit was measured at eight fixed fields and found to decrease from 18me to 8me as the field increases from 12 to 22 T. The observed Fermi surface is very similar to that of LaB6, indicating that the f-electrons are largely local rather than itinerant in CeB6, a picture confirmed by bandstructure calculations. The observed field dependence of the cyclotron mass is consistent with the low-energy scale of the system as measured, for example, by the Kondo temperature. Our results are compared with Fermi surface observations in other heavy fermion systems

MAGNETIC FIELD DEPENDENCE OF THE CYCLOTRON MASS IN THE KONDO LATTICE CeB6

The conduction-electron mass in the Kondo lattice system CeB6 is found to be strongly field dependent. CeB6 is an ordered heavy moment electron system with a zero field electronic specific heat coefficient of about 250 mJ/mole K2. Using the de Haas-van Alphen effect at temperatures as low as 60 mK in steady magnetic fields as large as 22 T, we observe a cyclotron orbit of frequency 8 680 T for fields along the [100] direction. The mass of this orbit was measured at eight fixed fields and found to decrease from 18 to 8 me as the field increases from 12 to 22 T. The field dependence of the cyclotron mass is consistent with recent specific heat results. The Fermi surface geometry is similar to that of LaB6, except that the extremal cross-sectional areas observed are 10 % larger than in LaB6. The f-electrons are therefore largely local rather than itinerant in CeB6, a picture confirmed by bandstructure calculations. The geometry of the Fermi surface does not depend on field. The observed field dependence of the cyclotron mass is consistent with the low energy scale of the system as measured, for example, by the Kondo temperature

Suppression of the mass enhancement in ceb6 in high magnetic fields

The effective mass of the itinerant electrons in the Kondo lattice system CeB6 is found to be strongly field dependent. Measurements of the de Haas-van Alphen effect at temperatures down to 60 mK in steady magnetic fields up to 22 T show a change of more than 100% in the cyclotron effective mass, decreasing with increasing field. The origin of the effect is not known but it is noted that a field of about 10 T corresponds to the energy scales in the system. © 1987 The Japan Society of Applied Physics

Magnetic field dependence of the many-body enhancement on the Fermi surface of CeB6

Low-temperature high-field specific heat measurements are presented which show that the density of states of the itinerant electrons in the Kondo lattice CeB6 decreases strongly with field. CeB6 is an ordered heavy electron system with a zero field electronic specific heat coefficient γ of about 250 mJ/mol K2. The specific heat was measured with the heat pulse method at temperatures as low as 0.3 K and in steady magnetic fields as high as 22 T. At 22 T the linear term in the specific heat was found to be five times smaller than in zero field. The observed field dependence in the electronic specific heat is in good agreement with the field dependence of the cyclotron mass recently found in de Haas-van Alphen experiments. © 1988