What do polarized student evaluation results say about my teaching?
Evaluations only tell you whether your students liked you or not.  Your main goal, however, is to have students learn the material and develop their intellectual skills, not to have them like you.

Have experienced colleagues sit in on your classes and give you feedback, and have colleagues look at your assessments and the students' performance on them (with appropriate attention given to how you prepared the students - at an extreme, assessments mean something different (but not nothing) if you've given the students the questions and answers in advance!).  This will give you much more useful information than student evaluations.