Hole-mediated interactions of Mn acceptors on GaAs (110) (invited)

Abstract

A scanning-tunneling-microscopy-substitution technique is used to incorporate single Mn atoms into Ga sites in GaAs ͑110͒ surfaces. The electronic states near a single Mn in the acceptor configuration produce a strong in-gap resonance associated with the acceptor level. The isolated Mn acceptor is probed in both p-type and n-type environments to access the neutral and ionized acceptor configurations. The Mn acceptor at the surface substitution site shares bulk characteristics that compare well with tight-binding calculations. The anisotropic structure of the Mn hole state plays an important role in hole-mediated interactions between the Mn acceptors. Isolated Mn pairs show a strong interaction dependence on crystal orientation and spacing. Certain pair orientations produce a strong splitting of the acceptor level into two levels with bondinglike and antibondinglike symmetries. A tight-binding model relates the acceptor level splitting and the spin-spin interaction energy J.

Magnetic interactions of substitutional Mn pairs in GaAs

“…For some Mn pairs, the wave functions of the two acceptor states have bonding and antibonding characters, which is again consistent with experiment. 4,5 These results support the validity of the kinetic p-d exchange model.…”

“…4,5 An antibonding character for the lower energy state is observed experimentally also for the Mn pair with the shortest separation. 5 While this does not seem to be case in our bulk ͗110͘ d=0.71a calculations ͑both states being essentially bond-ing͒, we do find that the value of the maximum LDOS on the As in between the Mn's is around twice as large for the upper acceptor wave function.…”

“…[4][5][6][7] Plots of the LDOS of the two acceptor levels in the ͑110͒ plane containing the two Mn are shown in Fig. 11 for the FM and in Fig.…”

“…[1][2][3][4][5][6][7] This effort was motivated in part by the hope that the high-resolution imaging and spatially resolved spectroscopic power of the STM could help in developing an accurate microscopic picture of dilute magnetic semiconductor ͑DMS͒ magnetism. In DMSs magnetic impurities provide local moments, which can couple to yield a collective ferromagnetic ͑FM͒ state.…”

“…Among the open issues in DMS physics 8 are the precise character of the hole states, the nature of the coupling of the holes with the local magnetic moments, and the properties of the ensuing magnetic interaction between local moments. STM experiments performed recently [4][5][6][7] are playing a decisive role in clarifying some of these issues.…”