Measurements of the Fermi surface are a fundamental technique for determining the electrical and magnetic properties of solids. In two-dimensional (2D) systems, the area and diameter of the Fermi surface are typically measured using Shubnikov–de Haas oscillations and commensurability oscillations respectively. However, these techniques are unable to detect changes in the parity of the Fermi surface [i.e., when $E(+k)\ne E(-k)]$. Here, we show that transverse magnetic focusing can be used to detect such changes, because focusing only measures a well defined section of the Fermi surface and does not average over $+k$ and $-k$. Furthermore, our results show that focusing is an order of magnitude more sensitive to changes in the Fermi surface than other 2D techniques. While we investigate a specific Fermi surface shift in this work, focusing could be used to investigate similar Fermi surface changes in other 2D systems.

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• Ballistic transport
• Carrier dynamics
• Fermi surface
• Magnetotransport
• Spin-orbit coupling
• III-V semiconductors
• Two-dimensional electron system
• Hall bar