TUNNELING TRANSMISSION IN 2 QUANTUM WIRES COUPLED BY A MAGNETICALLY DEFINED BARRIER

A numerical analysis of an electron waveguide coupler based on two qua ntum wires coupled by a magnetically defined barrier is presented with the use of the scattering-matrix method. For different geometry param eters and magnetic fields, tunneling transmission spectrum is obtained as a function of the electron energy. Different from that of conventi onal electron waveguide couplers, the transmission spectrum of the mag netically coupled quantum wires does not have the symmetry with regard to those geometrically symmetrical ports, It was found that the magne tic field in the coupling region drastically enhances the coupling bet ween the two quantum wires for one specific input port while it weaken s the coupling for the other input port. The results can be well under stood by the formation of the edge states in the magnetically defined barrier region. Thus, whether these edge states couple or decouple to the electronic propagation modes in the two quantum wires, strongly de pend on the relative moving directions of electrons in the propagating mode in the input port and the edge states in the magnetic region. Th is leads to a big difference in transmission coefficients between two quantum wires when injecting electrons via different input ports. Two important coupler specifications, the directivity and uniformity, are calculated which show that the system we considered behaves as a good quantum directional coupler. (C) 1997 American Institute of Physics.