Orthogonality Catastrophe and Spontaneous Symmetry Breaking in Double-layer Fermi-liquid-like States

TL;DR

This paper investigates how increasing tunneling strength in a double-layer Fermi-liquid system induces a first-order transition from an unpolarized to a polarized pseudospin state, highlighting the roles of orthogonality catastrophe and symmetry breaking.

Contribution

It demonstrates the existence of a first-order transition driven by tunneling strength in double-layer Fermi-liquid states, connecting orthogonality catastrophe effects with spontaneous symmetry breaking.

Findings

Transition from unpolarized to polarized pseudospin state with increasing tunneling

Orthogonality catastrophe renders weak tunneling effects irrelevant

First-order phase transition identified in the system

Abstract

The double-layer electron system with total filling factor $\nu=1/2$ can be regarded as two separate Fermi-liquid-like states with $\nu=1/4$ when the layer separation is sufficiently large and there is no tunneling. The weak tunneling in this state suffers an orthogonality catastrophe and it becomes irrelevant. Using the symmetric and antisymmetric combinations of layer indices as the pseudospin degrees of freedom, we show that there exists the first order transition from the above pseudospin unpolarized state to the pseudospin polarized Fermi-liquid-like state with $\nu=1/2$ as the tunneling strength becomes sufficiently large.