Wd. Sheng et al., TUNNELING TRANSMISSION IN 2 QUANTUM WIRES COUPLED BY A MAGNETICALLY DEFINED BARRIER, Journal of applied physics, 82(12), 1997, pp. 6083-6088
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.