A lateral valley tunnel junction controlled by ferroelectric polarization

A special class of valleytronic two-dimensional (2D) semiconductors possesses carrier pockets ( i.e. , valleys ) along certain directions in the Brillouin zone, which can be applied as a new freedom for information storage and processing. Here we show that members of this family that are ferroelectric allow the location of these valleys to be switched by rotating the ferroelectric polarization. This makes possible a valley tunnel junction by creating or eliminating valley matching in reciprocal space. A lateral valley tunnel junction is formed from monolayer-thick ferroelectric SnTe as the electrodes and nanometer-wide paraelectric PbTe as the tunnel barriers, both grown by molecular beam epitaxy. We show, using scanning tunneling microscopy, that the transmission probability of the 2D electronic states at the valence band maximum of SnTe monolayer strongly relies on the relative orientation between the polarization directions of the two SnTe electrodes. The transmission can be switched from a suppressed state to a permitted state by rotating the ferroelectric polarization of one SnTe electrode by 90 degrees. Our work demonstrates the electric-field-control of valley locations and its potential for tunnel junction valleytronic devices.