Momentum dependence of superconducting gap, strong-coupling dispersion kink, and tightly bound Cooper pairs in the high- Tc (Sr,Ba) 1-x(K,Na)xFe2As2 superconductors
Momentum dependence of superconducting gap, strong-coupling dispersion kink, and tightly bound Cooper pairs in the high- Tc (Sr,Ba) 1-x(K,Na)xFe2As2 superconductors
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DOI：
10.1103/physrevb.78.184508
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发表时间：
2008-11
影响因子：
3.7
通讯作者：
L. Wray;D. Qian;D. Hsieh;Y. Xia;L. Li;J. Checkelsky;A. Pasupathy;K. Gomes;C. Parker;A. Fedorov;G. Chen;J. Luo;A. Yazdani;N. Ong;N. L. Wang;M Zahid Hasan
中科院分区：
文献类型：
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作者：
L. Wray;D. Qian;D. Hsieh;Y. Xia;L. Li;J. Checkelsky;A. Pasupathy;K. Gomes;C. Parker;A. Fedorov;G. Chen;J. Luo;A. Yazdani;N. Ong;N. L. Wang;M Zahid Hasan
我们对高温超导体类 (Sr/Ba)_(1−x)K_xFe_2As_2 进行了系统的角分辨光电发射光谱研究。通过利用光子能量调制对比和散射几何结构，我们报告了费米表面和超导能隙的动量依赖性，Δ(k)。在超导态下，在 25-55 meV 的结合能范围内观察到反映强散射过程的显着准粒子色散扭结，并且发现库珀对波函数的相干长度或范围约为 20 A，这不是通过 BCS 声子延迟机制实现的超导相的特征。观察到的 40±15 meV 扭结可能反映了 J_1-J_2 磁场背景中受挫自旋激发和软声子散射的贡献。共同得出的结果为配对电势的性质提供了直接线索，包括超导序参数中的内部相移因子，该因子导致强耦合设置中的布里渊区节点。
We present a systematic angle-resolved photoemission spectroscopic study of the high-Tc superconductor class (Sr/Ba)_(1−x)K_xFe_2As_2. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the superconducting gap, Δ(k ). A prominent quasiparticle dispersion kink reflecting strong scattering processes is observed in a binding-energy range of 25–55 meV in the superconducting state, and the coherence length or the extent of the Cooper pair wave function is found to be about 20 A, which is uncharacteristic of a superconducting phase realized by the BCS-phonon-retardation mechanism. The observed 40±15 meV kink likely reflects contributions from the frustrated spin excitations in a J_1-J_2 magnetic background and scattering from the soft phonons. Results taken collectively provide direct clues to the nature of the pairing potential including an internal phase-shift factor in the superconducting order parameter which leads to a Brillouin zone node in a strong-coupling setting.