Effects of heavy-ion irradiation on FeSe

Abstract

We report the effects of heavy-ion irradiation on FeSe single crystals by irradiating Uranium up to a dose equivalent matching field of B φ = 16 T. Almost continuous columnar defects along the c-axis with a diameter ∼10 nm are confirmed by high-resolution transmission electron microscopy. Tc is found to be suppressed by introducing columnar defects at a rate of dTc/dB φ ∼ -0.29KT −1 , which is much larger than those observed in iron pnictides. This unexpected large suppression of Tc in FeSe is discussed in relation to the large diameter of the columnar defects as well as its unique band structure with a remarkably small Fermi energy. The critical current density is first dramatically enhanced with irradiation reaching a value over ∼2×10 5 A/cm 2 (∼5 times larger than that of the pristine sample) at 2 K (self-field) with B φ = 2 T, then gradually suppressed with increasing B φ . The δl-pinning associated with charge-carrier mean free path fluctuations, and the δTc-pinning associated with spatial fluctuations of the transition temperature are found to coexist in the pristine FeSe, while the irradiation increases the contribution from δl-pinning, and makes it dominant over B φ = 4 T.

Glassy Dynamics in a heavy ion irradiated NbSe2 crystal

“…Much less is known about the effect of field orientation on the creep rate ( S ) and, more generally, creep in materials besides YBCO that contain CDs. For example, it is unknown why the peak associated with rapid double-kink expansion in YBCO has not been observed in other materials 18 – 22 . Of particular interest is superconductors with low Ginzburg numbers ( Gi ), such as NbSe 2 , which can attain significantly lower creep rates 23 than superconductors with high Gi , such as YBCO ( Gi ~ 10 −2 ).…”

(Li1−xFex)OHFeSe Superconductors: Crystal Growth, Structure, and Electromagnetic Properties

“…The K0.80Fe1.81Se2 precursor is a good superconductor, with a Tc of 31.76 (29.31) K derived from magnetic (electrical) measurements. After the hydrothermal ion-exchange process, its Tc is increased by 6.08 (13.38) K. Its zero field cooled (ZFC) susceptibility is nearly temperature independent before the onset of superconductivity, indicating that the normal state is Pauli paramagnetic, which can be found in the SC samples of (Li1−xFex)OHFeSe, AxFe2−ySe2 (A = K, Rb, and Cs), and FeSe [3,7,56,62,87,88]. The hump peak of the normalized resistance versus temperature (Rab/Rp-T) curve shifts from 220.79 K to 266.06 K and the resistivity of the hump peak is decreased from 560 mΩcm to 0.13 mΩcm due to the hydrothermal reaction.…”

Anomalous critical point behavior in dilute magnetic semiconductor (Ca,Na)(Zn,Yu1, Liu2, Zhao3 et al. 2020Phys. Rev. Materials4160View full textAdd to dashboardCite

“…One can then independently control the concentrations of localized spins and charge carriers, and study their respective roles in determining magnetic properties of such DMSsan important advantage over (Ga,Mn)As and related materials, in which such separation of the two key elements of ferromagnetism is not possible [24]. In particular, these features make the new DMSs with their independent carrier and spin dopingespecially attractive for testing and distinguishing between the various mechanisms proposed for magnetic interactions in DMS systems [25,26].…”