Observation of thermal transport close to diffusive in a weak long-ranged Fermi-Pasta-Ulam-Tsingou-type model

Abstract

We explore thermal transport in a one-dimensional Fermi-Pasta-Ulam-Tsingou-type (FPUT-type) system with long-range (LR) interactions. In such a system, the harmonic part of the potential is nearest-neighbor coupled, while the strength of the quartic part of the potential between two lattice sites decays as a power σ of the inverse of their distance, demonstrating the LR feature of the system. The relevant strong LR model (0≤σ≤1) has been considered in detail in our recent study [Xiong and Wang, ], and here, we focus on the weak LR regime (1≤σ≤3). We show that the thermal transport behaviors in this regime are quite unexpected. We discovered a subregime (1≤σ≤1.5) wherein the thermal transport behaviors are very close to diffusive. This suggests that even a momentum-conserving system with appropriate LR interactions can still exhibit normal heat conduction. By meticulously analyzing the space-time scaling properties of equilibrium heat correlations, we also determine the center of this diffusive thermal transport at approximately σ≃1.25. These discoveries, together with our prior results, provide a comprehensive understanding of thermal transport of this kind of LR-FPUT-type model. Published by the American Physical Society 2024