Unusual effects of Be doping in the iron-based superconductor FeSe
Unusual effects of Be doping in the iron-based superconductor FeSe
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DOI：
10.1088/1361-648x/aae3cf
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发表时间：
2018-10
期刊：
影响因子：
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通讯作者：
Jungsoo Kim;D. VanGennep;J. Hamlin;Xiaoping Wang;A. Sefat;G. Stewart
中科院分区：
文献类型：
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作者：
Jungsoo Kim;D. VanGennep;J. Hamlin;Xiaoping Wang;A. Sefat;G. Stewart
最近在SrTiO_3上的单层FeSe的超导转变温度(T_C)超过100K，重新引起了人们对体相母体化合物的兴趣。在KCl：AlCl3熔剂输运生长的FeSe0.94Be0.06、FeSe0.97Be0.03和FeSe晶体中，这项工作报告了使用Be-掺杂FeSe的情况，该掺杂是可能的最小掺杂剂之一，对应于有效的化学压力。根据晶格参数测量，6%的Be掺杂使四方FeSe晶格收缩，相当于0.75 Gpa的物理压力。采用这种助熔剂传输法制备样品时，Be的最大掺杂量为6%。在FeSe0.94Be0.06的最大成分下，晶胞收缩2.4%，比热法测得的体相T_c增加近10%，T_c-压力行为峰值下移~1 Gpa，T_s=89K附近的高温结构转变增加1.9K(相对于其他掺杂均匀抑制T_s的FeSe)，低温比热γ比纯FeSe提高10%。此外，掺杂6%后，剩余电阻率比ρ(300K)/ρ(T→0)增加了近4倍，而ρ(300K)/ρ()增加了50%。
Recent superconducting transition temperatures (Tc) over 100 K for monolayer FeSe on SrTiO3 have renewed interest in the bulk parent compound. In KCl:AlCl3 flux-transport-grown crystals of FeSe0.94Be0.06, FeSe0.97Be0.03 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 FeSe0.94Be0.06, the lattice unit cell shrinks by 2.4%, Tc—measured in the bulk via specific heat—increases by almost 10%, the Tc versus pressure behavior shifts its peak downwards by ~1 GPa, the high temperature structural transition around TS = 89 K increases by 1.9 K (in contrast to other dopants in FeSe which uniformly depress TS), 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() increases by 50%.