Tuning the superconductivity of thin FeSe in a diamond anvil cell
Jianyu Xie1, Xinyou Liu1, Wei Zhang1, Sum Ming Wong1, Xuefeng Zhou2, Yusheng Zhao2, Shanmin Wang2, Kwing To Lai1, *Swee K. Goh1

In this talk, I will present a methodology for conducting magnetotransport measurements on thin flakes of layered materials using a diamond anvil cell (Figure (a)). With this technique, we conducted a series of high-pressure experiments on FeSe thin flakes. We find that, as the thickness decreases, the nematic phase boundary on temperature-pressure phase diagrams remains robust while the magnetic order is significantly weakened. A local maximum of Tc is observed outside the nematic phase region, not far from the extrapolated nematic endpoint in all samples. However, the maximum Tc value is reduced associated with the weakening of magnetism. No high-Tc phase is observed in the thinnest sample (Figure (b)). Our results suggest that nematic fluctuations alone can only have a limited effect while magnetic fluctuations are pivotal on the enhancement of Tc in FeSe.

Keywords: Diamond anvil cell, FeSe,  Phase diagrams