FeSe_(0.36)S_(0.64)超导单晶的制备、表征及电输运特性  

Synthesis, Characterization and Transport Properties of Superconducting Fe_(0.36)S_(0.64) Single Crystal

作　　者：秦玲瑶 Qin Lingyao(Shijiazhuang Campus of the Army Infantry Academy,Shijiazhuang 050000,China)

机构地区：[1]陆军步兵学院石家庄校区,河北石家庄050000

出　　处：《稀有金属材料与工程》2021年第2期654-657,共4页Rare Metal Materials and Engineering

摘　　要：FeSe超导体的基态由于不存在长程磁有序,在结构相变处伴随着液晶相电子态的转变,使得该体系成为研究铁基超导体中液晶相电子态与非常规超导电性之间关联的重要体系。以前的研究发现,在等价位S元素掺杂的FeSe1-xSx中,液晶相被逐渐抑制,在量子临界点(x≈0.17)附近,液晶相完全消失,超导能隙结构也发生显著变化,说明液晶相与超导电子配对之间有着重要的关联。在FeSe1-xSx样品中,用传统的固相反应法和气相输运法,最大掺杂量仅能到x≈0.21,这限制了对该体系液晶相消失后高掺杂区域(x>0.21)的物性研究。本实验通过水热法制备出了高掺杂含量的FeSe_(0.36)S_(0.64)超导单晶样品,通过电阻测量FeSe0.36S0.64的超导转变温度大约为5 K。为了进一步研究FeSe_(0.36)S_(0.64)的正常态电子行为,还对其进行详细的磁电阻和霍尔效应分析。结果发现,磁电阻违背Kohler定理的标度,这可能与载流子浓度随着温度发生变化或者多带效应有关。另外,霍尔效应测量发现,该体系电输运受电子型载流子的主导,霍尔系数在120K以下出现非单调的变化行为,表明该体系低温下有着明显的多带效应。优化的水热法对制备不同掺杂S含量的FeSe1-xSx单晶以及研究该体系的非常规超导电性有着重要的意义。FeSe has a unique ground state in which superconductivity coexists with a nematic order but without long-range magnetic ordering, providing a significant opportunity to investigate the correlation between the nematic phase and the unconventional superconductivity in iron-based superconductors(IBSs). Previous studies have shown that the nematic phase was gradually suppressed by isovalent S substitution in FeSe_(1-x)S_(x), meanwhile, the superconducting gap structure abruptly changed once the nematic phase vanished at the quantum critical point x≈0.17, indicating that the nematic phase plays a key role on the pairing mechanism. Unfortunately, the crystals with S doping level x>0.21 have not been yet synthesized via the conventional crystal growth method until now, which limits the research of crystals with high doping levels. This work prepared FeSe_(0.36)S_(0.64) crystals with superconducting transition temperature Tc≈5 K using hydrothermal method. In order to get more insight into the normal state properties, the research presented the magnetoresistance and Hall effect measurements by six-probe method. It is found that the Kohler’s rule is strongly violated, and the negative Hall coefficient shows strong but nonmonotonic T-dependence below about 120 K, which may be intimately related with the multiband electronic structure in this system. The hydrothermal method is of great significance for the crystals growth of FeSe_(1-x)S_(x) with different S doping levels and the investigation of the unconventional superconductivity in 11-type IBSs.

关 键 词：FeSe1-xSx 水热法 超导电性 

分 类 号：TH142.8[一般工业技术—材料科学与工程] TM26[机械工程—机械制造及自动化]