Free Energy of the Quantum Sherrington-Kirkpatrick Spin-Glass Model with Transverse Field

TL;DR

This paper derives a formula for the free energy of the quantum Sherrington-Kirkpatrick spin-glass model with transverse field in the thermodynamic limit, using path integrals and vector-spin glass approximations.

Contribution

It provides a novel formula for the quantum SK model's free energy valid for all inverse temperatures, extending classical results via vector-spin glass approximations.

Findings

Derived a formula for the free energy in the thermodynamic limit.

Connected the quantum model's free energy to classical vector-spin glasses.

Extended Parisi formula to quantum spin glasses.

Abstract

We consider the quantum Sherrington-Kirkpatrick (SK) spin-glass model with transverse field and provide a formula for its free energy in the thermodynamic limit, valid for all inverse temperatures $\beta>0$. To characterize the free energy, we use the path integral representation of the partition function and approximate the model by a sequence of finite-dimensional vector-spin glasses with $\mathbb{R}^d$-valued spins. This enables us to use results of Panchenko who generalized in \cite{Pan2,Pan3} the Parisi formula to classical vector-spin glasses. As a consequence, we can express the thermodynamic limit of the free energy of the quantum SK model as the $d\to\infty$ limit of the free energies of the $d$-dimensional approximations of the model.