The extended diffusive Sachdev-Ye-Kitaev model as a sort of "strange metal"

TL;DR

This paper extends the SYK model to higher dimensions, studying collective bosonic excitations that behave as neutral diffusive energy modes, contributing to the strange metal behavior and thermalization in strongly correlated systems.

Contribution

It introduces a higher-dimensional extension of the SYK model with ultraviolet corrections, analyzing collective bosonic excitations as diffusive energy modes in a specific temperature regime.

Findings

Identified neutral diffusive energy excitations with temperature-dependent lifetime.

Confirmed linear T increase of particle current through hydrodynamic modeling.

Suggested a connection to Marginal Fermi Liquid behavior in interacting quantum liquids.

Abstract

The 0+1-d Sachdev-Ye-Kitaev (SYK) fermionic model attracts nowadays a wide spread interest of the Condensed Matter community, as a benchmark toy model for strong electron correlation and non Fermi Liquid behavior. It is exactly solvable in the infrared limit and reproduces the linear dependence of the resistivity on temperature T, in linear response, typical of the strange metal phase of High Temperature Superconducting (HTS) materials. The breaking of its conformal symmetry requires ultraviolet corrections for a faithful description of its pseudo Goldstone Modes. Extension of the model to higher space dimension includes a local U(1) phase generating collective bosonic excitations driven by the additional ultraviolet contribution to the action. These excitations are studied here, in a temperature window of incoherent dynamics in which the expected chaotic regime has not yet taken over. We identify them as neutral diffusive energy excitations with temperature dependent lifetime h / k_B T. They provide thermalization of the system and contribute to the T dependence of the transport coefficients. The linear unbound T increase of particle current is confirmed by our hydrodynamic modelization. A quantum liquid in interaction with this system would become a Marginal Fermi Liquid.