Magnetic and electric control of spin- and valley-polarized transport across tunnel junctions on monolayer WSe2

Abstract

The recent experimental realization of high-quality WSe2 leads to the possibility of an efficient manipulation of its spin and valley degrees of freedom. Its electronic properties comprise a huge spin-orbit coupling, a direct band gap, and a strong anisotropic lifting of the degeneracy of the valley degree of freedom in a magnetic field. We evaluate its band structure and study ballistic electron transport through single and double junctions (or barriers) on monolayer WSe2 in the presence of spin M-s and valley M-v Zeeman fields and of an electric potential U. The conductance versus the field Ms or Mv decreases in a fluctuating manner. For a single junction, the spin P-s and valley P-v polarizations rise with M = M-v = 2M(s), reach a value of more than 55%, and become perfect above U approximate to 45 meV while for a double junction this change can occur for U >= 50 meV and M >= 5 meV. In certain regions of the (M, U) plane P-v becomes perfect. The conductance g(c), its spin-up and spin-down components, and both polarizations oscillate with the barrier width d. The ability to isolate various carrier degrees of freedom in WSe2 may render it a promising candidate for new spintronic and valleytronic devices.