Nano Research

Article Title

Scanning gate imaging of quantum point contacts and the origin of the 0.7 anomaly


two-dimensional electron gas (2-DEG), scanning gate microscopy, 0.7 anomaly


The origin of the anomalous transport feature appearing at a conductance G 0.7 × (2e2/h) in quasi-1D ballistic devices–the so-called 0.7 anomaly–represents a long standing puzzle. Several mechanisms have been proposed to explain it, buta general consensus has not been achieved. Proposed explanations have been based on quantum interference, the Kondo effect, Wigner crystallization, and other phenomena. A key open issue is whether the point defects that can occur in these low-dimensional devices are the physical cause behind this conductance anomaly. Here we adopt a scanning gate microscopy technique to map individual impurity positions in several quasi-1D constrictions and correlate these with conductance characteristics. Our data demonstrate that the 0.7 anomaly can be observed irrespective of the presence of localized defects, and we concludethat the 0.7 anomaly is a fundamental property of low-dimensional systems.

Graphical Abstract


Tsinghua University Press