Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe

We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 T applied parallel to the ab plane. At low temperatures, the upper critical field μ_{0}H_{c2}^{ab} shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ_{0}H^{*}≈24  T well below μ_{0}H_{c2}^{ab}, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties. We attribute the high-field phase to the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.

Quantum Vortex Core and Missing Pseudogap in the Multiband BCS-BEC Crossover Superconductor FeSe

FeSe is argued as a superconductor in the Bardeen-Cooper-Schrieffer Bose-Einstein condensation crossover regime where the superconducting gap size and the superconducting transition temperature T_{c} are comparable to the Fermi energy. In this regime, vortex bound states should be well quantized and the preformed pairs above T_{c} may yield a pseudogap in the quasiparticle-excitation spectrum. We performed spectroscopic-imaging scanning tunneling microscopy to search for these features. We found Friedel-like oscillations near the vortex, which manifest the quantized levels, whereas the pseudogap was not detected. These apparently conflicting observations may be related to the multiband nature of FeSe.

Associations of insulin-like growth factor-I and insulin-like growth factor binding protein-3 with bone quality in the general adult population

OBJECTIVE

Growth hormone (GH) and its main mediator, insulin-like growth factor-I (IGF-I), play a significant role in bone metabolism. The relations between IGF-I and bone mineral density (BMD) or osteoporosis have been assessed in previous studies but whether the associations are sex-specific remains uncertain. Moreover, only a few studies examined bone quality assessed by quantitative ultrasound (QUS). We aimed to investigate these associations in the general population of north-east Germany.

DESIGN AND MEASUREMENTS

Data from 1759 men and 1784 women who participated in the baseline examination of the Study of Health in Pomerania (SHIP)-Trend were used. IGF-I and IGF-binding protein-3 (IGFBP-3) concentrations were measured on the IDS-iSYS multidiscipline automated analyser (Immunodiagnostic Systems Limited). QUS measurements were performed at the heel (Achilles InSight, GE Healthcare). Sex-specific linear and multinomial logistic regression models adjusted for potential confounders were calculated.

RESULTS

Linear regression analyses revealed significant positive associations between IGF-I and IGF-I/IGFBP-3 ratio, a marker for free IGF-I, with all QUS parameters in men. Among women, we found an inverse association between IGF-I and the QUS-based fracture risk but no association with any other QUS parameter. There was no association between IGFBP-3 and the QUS-based fracture risk.

CONCLUSIONS

Our data suggest an important role of IGF-I on bone quality in men. The observed association of IGF-I with the QUS-based stiffness index and QUS-based fracture risk in this study might animate clinicians to refer patients with low IGF-I levels, particularly men, to a further evaluation of risk factors for osteoporosis and a detailed examination of the skeletal system.

How to Reach a Thousand-Second in-Plane Polarization Lifetime with 0.97-GeV/c Deuterons in a Storage Ring

We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10^{-29}  e cm.