Semiconductor devices rely on the charge and spin of electrons, but there is another electronic degree of freedom called pseudospin in a two-level quantum system¹ such as a crystal consisting of two sublattices². A potential way to exploit the pseudospin of electrons in pseudospintronics^3,4,5 is to find quantum matter with tunable and sizeable pseudospin polarization. Here, we propose a bipolar pseudospin semiconductor, where the electron and hole states have opposite net pseudospin polarization. We experimentally identify such states in anisotropic honeycomb crystal—black phosphorus. By sublattice interference of photoelectrons, we find bipolar pseudospin polarization greater than 95% that is stable at room temperature. This pseudospin polarization is identified as a consequence of Dirac cones merged in the highly anisotropic honeycomb system^6,7. The bipolar pseudospin semiconductor, which is a pseudospin analogue of magnetic semiconductors, is not only interesting in itself, but also might be useful for pseudospintronics.

^{半导体器件依赖于电子的电荷和自旋，但在两能级量子系统1}例如由两个亚晶格组成的晶体²中，还有另一个称为赝自旋的电子自由度。一种利用赝自旋电子学中电子赝自旋的潜在方法^3,4,5是寻找具有可调和相当大的赝自旋极化的量子物质。在这里，我们提出了一种双极赝自旋半导体，其中电子和空穴状态具有相反的净赝自旋极化。我们通过实验确定了各向异性蜂窝晶体——黑磷中的这种状态。通过光电子的亚晶格干涉，我们发现双极赝自旋极化大于95%，在室温下是稳定的。^{这种赝自旋极化被确定为在高度各向异性蜂窝系统6,7}中合并的狄拉克锥的结果。双极赝自旋半导体是磁性半导体的赝自旋类似物，不仅本身很有趣，而且可能对赝自旋电子学有用。