Optical conductivity of a two-dimensional metal at the onset of spin-density-wave order

Article

关键词: HIGH-TEMPERATURE SUPERCONDUCTORS;    QUANTUM CRITICAL-POINT;    T-LINEAR RESISTIVITY;    CUPRATE SUPERCONDUCTORS;    NORMAL-STATE;    PSEUDOGAP;    SCATTERING;    TRANSPORT;    YBA2CU3O7;    SYSTEM;   

DOI  :  10.1103/PhysRevB.89.155126

来源: SCIE

【 摘 要 】

We consider the optical conductivity of a clean two-dimensional metal near a quantum spin-density-wave transition. Critical magnetic fluctuations are known to destroy fermionic coherence at hot spots of the Fermi surface but coherent quasiparticles survive in the rest of the Fermi surface. A large part of the Fermi surface is not really cold but rather lukewarm in a sense that coherent quasiparticles in that part survive but are strongly renormalized compared to the noninteracting case. We discuss the self-energy of lukewarm fermions and their contribution to the optical conductivity sigma(Omega), focusing specifically on scattering off composite bosons made of two critical magnetic fluctuations. Recent study [S. A. Hartnoll et al., Phys. Rev. B 84, 125115 (2011)] found that composite scattering gives the strongest contribution to the self-energy of lukewarm fermions and suggested that this may give rise to a non-Fermi-liquid behavior of the optical conductivity at the lowest frequencies. We show that the most singular term in the conductivity coming from self-energy insertions into the conductivity bubble s sigma' (Omega) alpha ln(3) Omega/Omega(1/3) is canceled out by the vertex-correction and Aslamazov-Larkin diagrams. However, the cancellation does not hold beyond logarithmic accuracy, and the remaining conductivity still diverges as 1/Omega(1/3). We further argue that the 1/Omega(1/3) behavior holds only at asymptotically low frequencies, well inside the frequency range affected by superconductivity. At larger Omega, up to frequencies above the Fermi energy, sigma 1 (Omega) scales as 1/Omega, which is reminiscent of the behavior observed in the superconducting cuprates.

【 授权许可】

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