The quasi-two-dimensional metal Sr2RuO4 is one of the best characterized unconventional superconductors, yet the nature of its superconducting order parameter is still under debate1–3. This ...information is crucial to determine the pairing mechanism of Cooper pairs. Here we use ultrasound velocity to probe the superconducting state of Sr2RuO4. This thermodynamic probe is sensitive to the symmetry of the material, and therefore, it can help in identifying the symmetry of the superconducting order parameter4,5. Indeed, we observe a sharp jump in the shear elastic constant c66 as the temperature is increased across the superconducting transition. This directly implies that the superconducting order parameter is of a two-component nature. On the basis of symmetry arguments and given the other known properties of Sr2RuO4 (refs. 6–8), we discuss which states are compatible with this requirement and propose that the two-component order parameter {dxz; dyz} is the most likely candidate.Ultrasound experiments show that the superconducting order parameter in strontium ruthenate must have two components.
Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the ...role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 and K0.76Fe1.72Se2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds from a metallic state to a phase where the dxy orbital loses all spectral weight while other orbitals remain itinerant. These observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors.
Short chain fatty acids (SCFAs) are the main products of indigestible carbohydrates that are fermented by microbiota in the hindgut. This study was designed to investigate the effects of oral SCFAs ...administration on the lipid metabolism of weaned pigs. A total of 21 barrows were randomly allocated into three groups, including control group (orally infused with 200 mL physiological saline per day), low dose SCFAs group (orally infused with 200 mL SCFAs containing acetic acid 20.04 mM, propionic acid 7.71 mM and butyric acid 4.89 mM per day), and high dose SCFAs group (orally infused with 200 mL SCFAs containing acetic acid 40.08 mM, propionic acid 15.42 mM and butyric acid 9.78 mM per day). The results showed that the average daily feed intake of SCFAs groups were lower than that of control group (P<0.05). Oral administration of SCFAs decreased the concentrations of triglyceride (TG), total cholesterol (TC), high density lipoprotein-cholesterol and insulin (P<0.05), and increased the leptin concentration in serum (P<0.05). The total fat, as well as TC and TG levels in liver, was decreased by oral SCFAs administration (P<0.05). In addition, SCFAs down-regulated the mRNA expressions of fatty acid synthase (FAS) and sterol regulatory element binding protein 1c (P<0.05), and enhanced the mRNA expression of carnitine palmitoyltransferase-1α (CPT-1α) in liver (P<0.05). SCFAs also decreased FAS, acetyl-CoA carboxylase (ACC) and peroxisome proliferator activated receptor σ mRNA expressions in longissimus dorsi (P<0.05). And in abdominal fat, SCFAs reduced FAS and ACC mRNA expressions (P<0.05), and increased CPT-1α mRNA expression (P<0.05). These results suggested that oral administration of SCFAs could attenuate fat deposition in weaned pigs via reducing lipogenesis and enhancing lipolysis of different tissues.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Double horn points to an exotic stateThe so-called Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, a particular kind of superconducting order in which the order parameter oscillates in space, has ...fascinated physicists because it is tricky to stabilize. Kinjo et al. used nuclear magnetic resonance (NMR) measurements to observe a signature of the FFLO state in the material strontium ruthenate (see the Perspective by Pavarini). The modulation in the superconducting order parameter caused a corresponding modulation of spin density, which resulted in a peculiar, double horn–shaped structure of NMR intensity for a certain range of temperatures and applied magnetic field. —JS
Odd-parity superconductivity in Sr2RuO4 NELSON, K. D; MAO, Z. Q; MAENO, Y ...
Science (American Association for the Advancement of Science),
11/2004, Letnik:
306, Številka:
5699
Journal Article
Recenzirano
Phase-sensitive measurements were made on Sr2RuO4 to establish unambiguously the odd-parity pairing in this material. The critical current of Au(0.5)In(0.5)-Sr2RuO4 superconducting quantum ...interference devices prepared on Sr2RuO4 single crystals was found to be a maximum for devices with junctions on the same side of the crystal and a minimum for devices with junctions on opposite sides, in the limit of zero magnetic flux; these findings indicate that the phase of the superconducting order parameter in Sr2RuO4 changes by pi under inversion. This result verifies the odd-parity pairing symmetry and the formation of spin-triplet Cooper pairs in Sr2RuO4.
Abstract
Spin-valley locking in monolayer transition metal dichalcogenides has attracted enormous interest, since it offers potential for valleytronic and optoelectronic applications. Such an exotic ...electronic state has sparsely been seen in bulk materials. Here, we report spin-valley locking in a Dirac semimetal BaMnSb
2
. This is revealed by comprehensive studies using first principles calculations, tight-binding and effective model analyses, angle-resolved photoemission spectroscopy measurements. Moreover, this material also exhibits a stacked quantum Hall effect (QHE). The spin-valley degeneracy extracted from the QHE is close to 2. This result, together with the Landau level spin splitting, further confirms the spin-valley locking picture. In the extreme quantum limit, we also observed a plateau in the
z
-axis resistance, suggestive of a two-dimensional chiral surface state present in the quantum Hall state. These findings establish BaMnSb
2
as a rare platform for exploring coupled spin and valley physics in bulk single crystals and accessing 3D interacting topological states.
We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped ...Ca_{3}Ru_{2}O_{7}. Such an insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings have important implications because a magnetic field usually stabilizes the insulating ground state in a Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities and spin-lattice-charge coupling. This study further provides a model approach to search for CMR systems other than manganites, such as Mott insulators in the vicinity of the boundary between competing phases.
Dirac fermions with highly dispersive linear bands1–3 are usually considered weakly correlated due to the relatively large bandwidths (W) compared to Coulomb interactions (U). With the discovery of ...nodal-line semimetals, the notion of the Dirac point has been extended to lines and loops in momentum space. The anisotropy associated with nodal-line structure gives rise to greatly reduced kinetic energy along the line. However, experimental evidence for the anticipated enhanced correlations in nodal-line semimetals is sparse. Here, we report on prominent correlation effects in a nodal-line semimetal compound, ZrSiSe, through a combination of optical spectroscopy and density functional theory calculations. We observed two fundamental spectroscopic hallmarks of electronic correlations: strong reduction (1/3) of the free-carrier Drude weight and also the Fermi velocity compared to predictions of density functional band theory. The renormalization of Fermi velocity can be further controlled with an external magnetic field. ZrSiSe therefore offers the rare opportunity to investigate correlation-driven physics in a Dirac system.What happens to topological materials when their electrons are strongly interacting is an open question. Shao and others demonstrate that ZrSiSe is a material that can address this as it has a topological band structure and non-trivial correlations.
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