Composite fermions close to the one-half filling of the lowest Landau level revisited

TL;DR

This paper rigorously models composite fermions near half-filling, accurately reproducing experimental SAW results and revealing a significant increase in electron band mass under these conditions, with implications for understanding two-dimensional electron systems.

Contribution

The study provides a microscopic theory-based explanation for SAW experimental results near nu_e=1/2, highlighting the importance of electron band mass increase and finite mean-free path.

Findings

Accurate reproduction of SAW experimental results near nu_e=1/2

Electron band mass m_b increases substantially under these conditions

Finite mean-free path l_0 is crucial for linear sigma_xx(q) behavior

Abstract

By strictly adhering to the microscopic theory of composite fermions for the Landau-level filling fractions nu_e = p/(2 p + 1), we reproduce, with remarkable accuracy, the surface-acoustic-wave (SAW)-based experimental results by Willett and co-workers concerning two-dimensional electron systems with nu_e close to 1/2. Our results imply that the electron band mass m_b, as distinct from the composite fermion mass m_*, must undergo a substantial increase under the conditions corresponding to nu_e approximately equal to 1/2. In view of the relatively low aerial electronic densities n_e to which the underlying SAW experiments correspond, our finding conforms with the experimental results by Shashkin et al. [Phys. Rev. B 66, 073303 (2002)], concerning two-dimensional electrons in silicon, that signal sharp increase in m_b for n_e decreasing below approximately 2 x 10^{11} cm^{-2}. We further establish that a finite mean-free path l_0 is essential for the observed linearity of the longitudinal conductivity sigma_{xx}(q) as deduced from the SAW velocity shifts.