FeSe_{1−δ} 단결정의 압력에 따른 초전도 성질 변화: Superconducting properties in FeSe_{1−δ} single crystals under pressure

by Ji-hye Kim (MS Candidate)

Wednesday Nov 18, 2015, 1:00 PM → 1:25 PM Asia/Seoul

216-1호 (제1과학관)

Clarifying the interplay between superconducting phase and others is regarded as a key factor to describe the unconventional pairing mecha- nism. We established the pressure-induced phase diagram of high quality FeSe1−δ single crystals up to 3.3 GPa by measuring electrical transports. Remarkably, an anomaly of temperature, Tx, is shown up near 0.8 GPa. Compared with previous muon spin resonance(μSR) and nuclear magnetic resonance(NMR) experiments, it is expected that the antiferromagnetic or- dering which is induced by pressurizing leads this anomalous change in RT curves. A coexisting region where Tx and a critical temperature, Tc, increase simultaneously is found in the phase diagram while, in general, Fe-based superconductor(FeBS) shows the competition behavior between supercon- ductivity and antiferromagnetism. An overall aspect of minus derivatives of upper critical fields, −dHc2/dt|t = 1, decreases with increasing pressure ex- cept the competing region from 0.8 GPa to 1.6 GPa where the Tx appears and Ts disappears, respectively. The sudden increasement of an activation energy, U0, occurs just before entering the competing region which implies that the vortex pinning energy can be enhanced by the magnetic ordering.

Thesis Advisor: Prof. Younjung Jo