Spectral property of the planar self-affine measures with three-element digit sets

Let the self-affine measure μ M , D {\mu_{M,D}} be generated by an expanding real matrix M = diag ⁡ ( ρ 1 - 1 , ρ 2 - 1 ) {M=\operatorname{diag}(\rho_{1}^{-1},\rho_{2}^{-1})} and an integer digit set D = { ( 0 , 0 ) t , ( α 1 , α 2 ) t , ( β 1 , β 2 ) t } {D=\{(0,0)^{t},(\alpha_{1},\alpha_{2})^{t},(\beta_{1},\beta_{2})^{t}\}} with α 1 ⁢ β 2 - α 2 ⁢ β 1 ≠ 0 {\alpha_{1}\beta_{2}-\alpha_{2}\beta_{1}\neq 0} . In this paper, the sufficient and necessary conditions for L 2 ⁢ ( μ M , D ) {L^{2}(\mu_{M,D})} to contain an infinite orthogonal set of exponential functions are given.