solver: fix terminal branch cut

usadelndsoc/solver.py

@@ -118,8 +118,8 @@ class Core:
         m = self._mask == MASK_TERMINAL
         tau3 = np.diag([1, 1, -1, -1])
         for i, j in zip(*np.where(m)):
-            M = self._Omega[i, j] + self._omega * tau3
-            Q = signm(M)
+            M = self._Omega[i, j] + 1j * self._omega * tau3
+            Q = 1j * signm(-1j * M)
             g = np.linalg.solve(np.eye(2) + Q[:2, :2], Q[:2, 2:])
             gt = np.linalg.solve(np.eye(2) - Q[2:, 2:], Q[2:, :2])
             Phi[i, j, 0] = g