Gap evolution in nu=1/2 bilayer quantum Hall systems

TL;DR

This paper investigates the evolution of quantum Hall states in bilayer systems at filling fraction 1/2, revealing a continuous transition in the ground state and explaining unusual activation energy behavior.

Contribution

It provides a numerical analysis of the gap evolution and characterizes the transition from two-component to one-component states in bilayer quantum Hall systems.

Findings

Ground state changes continuously with interlayer tunneling

Lowest excited state changes discontinuously

Activation energy shows an upward cusp as a function of tunneling

Abstract

Fractional quantum Hall states in bilayer system at total filling fraction $\nu=1/2$ are examined numerically under some ranges of the layer separation and interlayer tunneling. It is shown that the ground state changes continuously from two-component state to one-component state as the interlayer tunneling rate is increased, while the lowest excited state changes discontinuously. This fact explains observed unusual behavior of the activation energy which reveals upward cusp as a function of interlayer tunneling. Some trial wave functions for the ground state and quasihole states are inspected.