G. Li, R. R. Urbano, P. Goswami, C. Tarantini, B. Lv, P. Kuhns, A. P. Reyes, C. W. Chu, L. Balicas
Magnetometry measurements in high quality LiFeAs single-crystals reveal a change in the sign of the magnetic irreversibility in the vicinity of the upper critical $H_{c2}$, i.e. from a clear diamagnetic-like response dominated by the pinning of vortices, to a state with a considerably smaller paramagnetic-like irreversibility which disappears at $H_{c2}$. If diamagnetism results from screening super-currents, paramagnetism must result from currents circulating in the opposite sense, mimicking a field-dependent magnetic moment below $H_{c2}$. We conclude that the superconducting state of LiFeAs at high fields must break time-reversal and parity symmetries. A Ginzburg-Landau analysis indicates that the field could stabilize a gap wave-function with either $(d_{x^2 - y^2} + id_{xy})$ or $(p_x+ip_y)$ symmetry, implying that LiFeAs might display a field-induced topological superconducting state.
View original:
http://arxiv.org/abs/1208.4882
No comments:
Post a Comment