Hello,
I tried the code below, and it seems that it works with backpropagation.
x = torch.tensor([[1, 2], [3, 4]], requires_grad=True)
a, b = x.split(1)
a.requires_grad
>> True
a.grad_fn
>> <SplitBackward at 0x7f1ed6f25128>
out = torch.FloatTensor([])
torch.cat([out, a.expand(1,-1)])
>> tensor([[1., 2.]], grad_fn=<CatBackward>)