有限温度下Shiba子带隙态的光谱性质
Spectral properties of Shiba sub-gap states at finite temperatures
摘要：
利用数值重整化群（NRG）方法，分析了超导接触耦合的单杂质Anderson模型描述的磁性杂质谱函数的温度依赖性.随着温度的升高，光谱权重逐渐从$δ$峰（Shiba/Yu-Shiba-Rusinov/Andreev束缚态）转移到连续的子带背景，但两种光谱特征在任何有限温度下共存，即，$δ$峰本身持续到$Δ$级的温度。连续的背景是由于Bogoliubov准粒子的非弹性交换散射的杂质，它是热激活的，因为它需要一个有限的热人口的准粒子以上的差距。在单重态制度的强杂交（电荷波动制度），我们检测到的存在下，一个额外的子间隙结构的间隙边缘以下的热激活行为，但与激活能等于的Shiba状态激发能。这些峰可以暂时解释为Shiba束缚态，其由准粒子从热激发的子隙双峰Shiba态散射而产生，即，高等级的芝州
英文摘要：
Using the numerical renormalization group (NRG), we analyze the temperature dependence of the spectral function of a magnetic impurity described by the single-impurity Anderson model coupled to superconducting contacts. With increasing temperature the spectral weight is gradually transferred from the $δ$-peak (Shiba/Yu-Shiba-Rusinov/Andreev bound state) to the continuous sub-gap background, but both spectral features coexist at any finite temperature, i.e., the $δ$-peak itself persists to temperatures of order $Δ$. The continuous background is due to inelastic exchange scattering of Bogoliubov quasiparticles off the impurity and it is thermally activated since it requires a finite thermal population of quasiparticles above the gap. In the singlet regime for strong hybridization (charge-fluctuation regime) we detect the presence of an additional sub-gap structure just below the gap edges with thermally activated behavior, but with an activation energy equal to the Shiba state excitation energy. These peaks can be tentatively interpreted as Shiba bound states arising from the scattering of quasiparticles off the thermally excited sub-gap doublet Shiba states, i.e., as high-order Shiba states.
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