“…On the other hand, through the initial works [24,25,33], it is known in [1] that there exist 0 < β 1 , β 2 < ∞ [see (11), (12) for the definition] depending on W 1 (y), W 2 (y), μ 1 , μ 2 , such that for β ∈ (0, min{β 1 , β 2 }), there exists a vector solution U y given by the mountain pass theorem on the Nehari manifold {u ∈ (H 1 r ) 2 \{(0, 0)} | ∇ u L(y, u)u = 0} and for β ∈ (max{β 1 , β 2 }, ∞), there exists a vector solution U y given by the mountain pass theorem on the whole space (H 1 r ) 2 , which is a least energy solutions among all nontrivial solutions of (5). This implies that Morse index of the vector solution is 2 for β ∈ (0, min{β 1 , β 2 }) and 1 for β ∈ (max{β 1 , β 2 }, ∞).…”