It's known that the bit errors of polar codes with successive cancellation (SC) decoding are coupled. We call the coupled information bits the correlated bits. In this paper, concatenation schemes are studied for polar codes and LDPC codes. In a conventional concatenation scheme, to achieve a better BER performance, one can divide all Nlbits in a LDPC block into Nlpolar blocks to completely de-correlate the possible coupled errors. In this paper, we propose a novel interleaving scheme between a LDPC code and a polar code which breaks the correlation of the errors among the correlated bits. This interleaving scheme still keeps the simple SC decoding of polar codes while achieves a better BER performance than a direct concatenation of polar codes (with BP decoding) with LDPC codes. The proposed scheme also achieves a comparable BER performance (0.5dB difference) at a much smaller delay compared with a Nlblock delay scheme.