Kim J S, VanGennep D, Hamlin J J, Wang X, Sefat A S, Stewart G R
Department of Physics, University of Florida, Gainesville, FL 32611, United States of America.
J Phys Condens Matter. 2018 Nov 7;30(44):445701. doi: 10.1088/1361-648X/aae3cf. Epub 2018 Sep 24.
Recent superconducting transition temperatures (T ) over 100 K for monolayer FeSe on SrTiO have renewed interest in the bulk parent compound. In KCl:AlCl flux-transport-grown crystals of FeSeBe, FeSeBe and, for comparison, FeSe, this work reports doping of FeSe using Be-among the smallest of possible dopants, corresponding to an effective 'chemical pressure'. According to lattice parameter measurements, 6% Be doping shrank the tetragonal FeSe lattice equivalent to a physical pressure of 0.75 GPa. Using this flux-transport method of sample preparation, 6% of Be was the maximum amount of dopant achievable. At this maximal composition of FeSeBe, the lattice unit cell shrinks by 2.4%, T -measured in the bulk via specific heat-increases by almost 10%, the T versus pressure behavior shifts its peak [Formula: see text] downwards by ~1 GPa, the high temperature structural transition around T = 89 K increases by 1.9 K (in contrast to other dopants in FeSe which uniformly depress T ), and the low temperature specific heat γ increases by 10% compared to pure FeSe. Also, upon doping by 6% Be the residual resistivity ratio, ρ(300 K)/ρ(T → 0), increases by almost a factor of four, while ρ(300 K)/ρ([Formula: see text]) increases by 50%.
近期，在SrTiO上的单层FeSe的超导转变温度（T）超过100 K，这重新引发了人们对其体相母体化合物的兴趣。在通过KCl:AlCl助熔剂传输生长的FeSeBe、FeSeBe以及作为对比的FeSe晶体中，本研究报道了使用Be对FeSe进行掺杂——Be是可能的最小掺杂剂之一，这相当于一种有效的“化学压力”。根据晶格参数测量，6%的Be掺杂使四方晶系的FeSe晶格收缩，相当于0.75 GPa的物理压力。使用这种助熔剂传输法制备样品时，6%的Be是可实现的最大掺杂量。在FeSeBe的这一最大组成下，晶格晶胞收缩2.4%，通过比热在体相中测量的T升高近10%，T与压力的关系曲线的峰值[公式：见正文]向下移动约1 GPa，89 K左右的高温结构转变升高1.9 K（与FeSe中其他均匀降低T的掺杂剂形成对比），并且与纯FeSe相比，低温比热γ增加10%。此外，在掺杂6%的Be后，剩余电阻率比ρ(300 K)/ρ(T→0)增加近四倍，而ρ(300 K)/ρ([公式：见正文])增加50%。
