I figure out what is cause my error! In fact, is in using norbs = 1, the correct form is norbs = 2: one orbital to spin up and other to spin down and also in lead construction where is to use conservation_law=-sigma_z
with these fixs my code is working now! In this thread i explain better (and with code exemples) how these fixs works: https://mail.python.org/archives/list/kwant-discuss@python.org/thread/YYOG27S6PAIBI3G2T5OQGKTVCE6G7D2X/#YYOG27S6PAIBI3G2T5OQGKTVCE6G7D2X
