物性セミナー/2025-7-3

2025年夏学期第８回物性セミナー

講師 Simone Fratini 氏（Institut Néel, CNRS and UGA, Grenoble)

題目 Strange metal transport from coupling to fluctuating spins

日時 2025年 7月 3日【木: いつもと違う曜日に注意】午後4時50分-6時15分程度

場所 16号館 827　およびオンライン

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Metals hosting strong electronic interactions, including high-temperature superconductors,behave in ways that do not conform to the normal Fermi liquid theory. To pinpoint the microscopic origin of this ”strange metal” behavior, here we reexamine the d.c. and frequency-dependent conductivity of the two-dimensional t-J model taking advantage of recent improvements made on the finite temperature Lanczos method, enabling numerically exact calculations at unprecedentedly low temperatures and high spectral resolution [1]. We find that strange metallicity is pervasive in the temperature-doping phase diagram wherever anti-ferromagnetic correlations are suppressed, being instead driven by paramagnetic spin fluctuations and unrelated to quantum criticality. Our results precisely characterize the Planckian carriers responsible for both the strange metal resistivities and the unconventional optical conductivities seen in experiments. In this regard, we propose an analytical, ”stretched Drude" formula, σ(ω)=σ_0/(1+(ωτ_opt )^c) , that closely reproduces the optical experiments in many correlated materials, providing a viable alternative to the popular extended Drude and multi-component analyses. Based on our numerical results, we propose a minimal one-particle-in-a-quantum-soup model that reproduces the transport mechanism of correlated systems.

参考文献:

[1] S. Fratini, A. Ralko, and S. Ciuchi, arXiv:cond-mat/2412.04322 (2024).

[2] S. Fratini, in preparation.