Unlike the parent phases of the iron-arsenide high-Tc superconductors, undoped FeSe is not magnetically ordered and exhibits superconductivity with Tc approximately 9 K. Equally surprising is the fact that applied pressure dramatically enhances the modest Tc to approximately 37 K. We investigate the electronic properties of FeSe using 77Se NMR to search for the key to the superconducting mechanism. We demonstrate that the electronic properties of FeSe are very similar to those of electron-doped FeAs superconductors, and that antiferromagnetic spin fluctuations are strongly enhanced near Tc. Furthermore, applied pressure enhances spin fluctuations. Our findings suggest a link between spin fluctuations and the superconducting mechanism in FeSe.
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http://dx.doi.org/10.1103/PhysRevLett.102.177005 | DOI Listing |
Adv Mater
January 2025
State Key Laboratory for Manufacturing Systems Engineering, Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, School of Electronic Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Large low-field magnetoresistance (LFMR, < 1 T), related to the spin-disorder scattering or spin-polarized tunneling at boundaries of polycrystalline manganates, holds considerable promise for the development of low-power and ultrafast magnetic devices. However, achieving significant LFMR typically necessitates extremely low temperatures due to diminishing spin polarization as temperature rises. To address this challenge, one strategy involves incorporating Ruddlesden-Popper structures (ABO):AO, which are layered derivatives of perovskite structure capable of potentially inducing heightened magnetic fluctuations at higher temperatures.
View Article and Find Full Text PDFNPJ Quantum Mater
January 2025
NIST Center for Neutron Research, Gaithersburg, MD 20899 USA.
The detailed anisotropic dispersion of the low-temperature, low-energy magnetic excitations of the candidate spin-triplet superconductor UTe is revealed using inelastic neutron scattering. The magnetic excitations emerge from the Brillouin zone boundary at the high symmetry and points and disperse along the crystallographic -axis. In applied magnetic fields to at least = 11 T along the , the magnetism is found to be field-independent in the ( 0) plane.
View Article and Find Full Text PDFNat Commun
January 2025
Institute of Solid State Physics, TU Wien, 1040, Vienna, Austria.
Waterfalls are anomalies in the angle-resolved photoemission spectrum where the energy-momentum dispersion is almost vertical, and the spectrum strongly smeared out. These anomalies are observed at relatively high energies, among others, in superconducting cuprates and nickelates. The prevalent understanding is that they originate from the coupling to some boson, with spin fluctuations and phonons being the usual suspects.
View Article and Find Full Text PDFChem Commun (Camb)
January 2025
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China.
Layered transition metal oxide (NaTMO) cathodes are considered highly appropriate for the practical applications of sodium-ion batteries (SIBs) owing to their facile synthesis and high theoretical capacity. Generally, the phase evolution behaviors of NaTMO during solid-state reactions at high temperature closely related to their carbon footprint, prime cost, and the eventual electrochemical properties, while the thermal stability in various desodiated states associated with wide temperature fluctuations are extremely prominent to the electrochemical properties and safety of SIB devices. Therefore, in this review, the influences of sintering conditions such as pyrolysis temperature, soaking time, and cooling rates on the phase formation patterns of NaTMO are summarized.
View Article and Find Full Text PDFNature
January 2025
Max-Planck-Institut für Quantenoptik, Garching, Germany.
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