diff --git a/codes/utils.py b/codes/utils.py
index c2b1f4265775b28f64f5f25bfcd83bbfbe8b95e1..442437d3f29c2b54abd2a9071d27a3f6bac69dc8 100644
--- a/codes/utils.py
+++ b/codes/utils.py
@@ -181,7 +181,7 @@ def model2hk(tb_model):
         ham = 0
         for vector in tb_model.keys():
             ham += tb_model[vector] * np.exp(
-                1j * np.dot(k, np.array(vector, dtype=float))
+                -1j * np.dot(k, np.array(vector, dtype=float))
             )
         return ham