Kumar K Santhosh, Lee Dooyong, Varshney Shivasheesh, Jalan Bharat, Armitage N P
Institute for Quantum Matter and Department of Physics and Astronomy, <a href="https://ror.org/00za53h95">John Hopkins University</a>, Baltimore, Maryland 21218, USA.
Department of Chemical Engineering and Materials Science, <a href="https://ror.org/017zqws13">University of Minnesota</a>, Minneapolis, Minnesota 55455, USA.
Phys Rev Lett. 2024 Sep 27;133(13):136003. doi: 10.1103/PhysRevLett.133.136003.
The mechanism of superconductivity in materials with aborted ferroelectricity and its emergence out of a dilute metallic phase in systems like doped SrTiO_{3} is an outstanding issue in condensed matter physics. This dilute metal has anomalous properties that are both similar and different to those found in the normal state of other unconventional superconductors. For instance, T^{2} resistivity can be found at densities that are too small to allow current decay through electron-electron scattering. We have investigated the optical properties of the dilute metallic phase in doped SrTiO_{3} using THz time-domain spectroscopy. At low frequencies the THz response exhibits a Drude-like form as expected for typical metal-like conductivity. We observed the frequency and temperature dependencies to the low energy scattering rate Γ(ω,T)∝(ℏω)^{2}+(pπk_{B}T)^{2} expected in a conventional Fermi liquid. However, we find the lowest known p values of 0.39-0.72. As p is 2 in a canonical Fermi liquid and existing models based on energy dependent elastic scattering bound p from below to 1, our observation lies outside current explanation. Our data also give insight into the high temperature regime and show that the temperature dependence of the resistivity derives in part from strong T dependent mass renormalizations.
在具有受挫铁电性的材料中，超导机制以及其在诸如掺杂SrTiO₃等体系中从稀金属相的出现，是凝聚态物理中的一个突出问题。这种稀金属具有一些异常性质，这些性质与其他非常规超导体正常态中的性质既有相似之处，又有不同之处。例如，在密度小到无法通过电子 - 电子散射使电流衰减的情况下，可以发现T²电阻率。我们使用太赫兹时域光谱研究了掺杂SrTiO₃中稀金属相的光学性质。在低频下，太赫兹响应呈现出类似德鲁德模型的形式，这是典型金属类导电性所预期的。我们观察到了与常规费米液体中预期的低能散射率Γ(ω,T)∝(ℏω)²+(pπk₈T)²的频率和温度依赖性。然而，我们发现p的最低已知值为0.39 - 0.72。由于在规范费米液体中p为2，并且基于能量依赖弹性散射的现有模型将p从下方限制到1，我们的观察结果超出了当前的解释范围。我们的数据还深入了解了高温区域，并表明电阻率的温度依赖性部分源于强烈的与温度相关的质量重整化。
