Linear response theory for cavity QED materials at arbitrary light-matter coupling strengths

Román-Roche, Juan (Universidad de Zaragoza) ; Gómez-León, Álvaro ; Luis Vitalla, Fernando ; Zueco, David

Resumen: We develop a linear response theory for materials collectively coupled to a cavity that is valid in all regimes of light-matter coupling, including symmetry-broken phases. We present and compare two different approaches. First, we use a coherent path-integral formulation for the partition function to obtain thermal Green's functions. This approach relies on a saddle-point expansion for the action that can be truncated in the thermodynamic limit. Second, we formulate the equations of motion for the retarded Green's functions and solve them. We use a mean-field decoupling of high-order Green's functions to obtain a closed, solvable system of equations. Both approaches yield identical results in the calculation of response functions for the cavity and material. These are obtained in terms of the bare cavity and material responses. In combination, the two techniques clarify the validity of a mean-field decoupling in correlated light-matter systems and provide complementary means to compute finite-size corrections to the thermodynamic limit. The theory is formulated for a general model that encompasses most of the systems typically considered in the field of cavity QED materials. Finally, we provide a detailed application of the theory to the quantum Hall effect and to a collection of spin models.

Idioma: Inglés

DOI: 10.1103/PhysRevB.111.035156

Año: 2025

Publicado en: Physical Review B 111, 3 (2025), 035156 [21 pp.]
ISSN: 2469-9950

Financiación: info:eu-repo/grantAgreement/ES/AEI/CEX2023-001286-S
Financiación: info:eu-repo/grantAgreement/ES/DGA/E09-17R-Q-MAD
Financiación: info:eu-repo/grantAgreement/EUR/MICINN/TED2021-131447B-C21

Tipo y forma: Article (PostPrint)

Área (Departamento): Área Física Teórica (Dpto. Física Teórica)