Anomalous spatial shifts in interface electronic reflection beyond linear approximation

TL;DR

This paper investigates anomalous spatial shifts in interface electronic reflection beyond the linear approximation, revealing that non-physical divergences are due to state changes and can be corrected by higher-order calculations, with implications for understanding beam shifts.

Contribution

It demonstrates that linear approximation can cause divergences in spatial shift calculations and proposes a method to resolve this by going beyond linear order, clarifying the approximation's limitations.

Findings

Linear approximation can lead to divergent shifts at critical angles.

Higher-order calculations resolve non-physical divergences.

Beam width influences the magnitude of spatial shifts near critical angles.

Abstract

Recently, the electronic analogy of the anomalous spatial shift, including Goos-H\"{a}nchen and Imbert-Fedorov effects, has been attracting widespread interest. The current research on the anomalous spatial shift in interface electronic reflection is based on the paradigm of linear approximation, under which the center position of the incident and reflected beams are obtained by expanding the phases of relevant basis states and scattering amplitudes to the first order of incident momentum. However, in a class of normal cases, the linear approximation can lead to a divergent spatial shift in reflection for certain incident angles even though the corresponding reflection possibility is finite. In this work, we show that such non-physical results are caused by an abrupt change in the number of the propagating states at critical parameters, and can be resolved by calculating the center positions of the scattering beams beyond the linear approximation. Moreover, we find that the beam width has an important influence on the spatial shift near the critical angles. We demonstrate our idea via concrete calculations of Goos-H\"{a}nchen and Imbert-Fedorov shift on two representative models. These results are beneficial for clarifying the scope of application of the linear approximation in the study of anomalous spatial shifts.