arXiv subjects

Zhi Wei Lin

Publications and source records attributed to Zhi Wei Lin.

3 recordsLinked to original sources

arXiv2010

Optical properties of the iron-chalcogenide superconductor FeTe0.55Se0.45

The complex optical properties of the iron-chalcogenide superconductor FeTe0.55Se0.45 with Tc=14K have been examined over a wide frequency range for light polarized in the Fe-Te(Se) planes above and below Tc. At room temperature the optical response may be described by a weakly-interacting Fermi liquid; however, just above Tc this picture breaks down and the scattering rate takes on a linear frequency dependence. Below Tc there is evidence for two gap features in the optical conductivity at Delta_1 ~ 2.5 meV and Delta_2 ~ 5.1 meV. Less than 20% of the free carriers collapse into the condensate for T << Tc, and this material is observed to fall on the universal scaling line for a BCS dirty-limit superconductor in the weak-coupling limit.

cond-mat.supr-con↗

arXiv2010

Effect of magnetic field on the spin resonance in FeTe(0.5)Se(0.5) as seen via inelastic neutron scattering

Inelastic neutron scattering and susceptibility measurements have been performed on the optimally-doped Fe-based superconductor FeTe(0.5)Se(0.5), which has a critical temperature, Tc of 14 K. The magnetic scattering at the stripe antiferromagnetic wave-vector Q = (0.5,0.5) exhibits a "resonance" at ~ 6 meV, where the scattering intensity increases abruptly when cooled below Tc. In a 7-T magnetic field parallel to the a-b plane, Tc is slightly reduced to ~ 12 K, based on susceptibility measurements. The resonance in the neutron scattering measurements is also affected by the field. The resonance intensity under field cooling starts to rise at a lower temperature ~ 12 K, and the low temperature intensity is also reduced from the zero-field value. Our results provide clear evidence for the intimate relationship between superconductivity and the resonance measured in magnetic excitations of Fe-based superconductors.

cond-mat.supr-con↗

arXiv2009

Short-range incommensurate magnetic order near the superconducting phase boundary in Fe(1+d)Te(1-x)Se(x)

We performed elastic neutron scattering and magnetization measurements on Fe(1.07)Te(0.75)Se(0.25) and FeTe(0.7)Se(0.3). Short-range incommensurate magnetic order is observed in both samples. In the former sample with higher Fe content, a broad magnetic peak appears around (0.46,0,0.5) at low temperature, while in FeTe(0.7)Se(0.3) the broad magnetic peak is found to be closer to the antiferromagnetic (AFM) wave-vector (0.5,0,0.5). The incommensurate peaks are only observed on one side of the AFM wave-vector for both samples, which can be modeled in terms of an imbalance of ferromagnetic/antiferromagnetic correlations between nearest-neighbor spins. We also find that with higher Se (and lower Fe) concentration, the magnetic order becomes weaker while the superconducting temperature and volume increase.

cond-mat.supr-con↗