How to fix gap between carpet and wall to prevent rodent?

Our condo is located in a forest/mountain area and we have suffered some rodent issues lately. We have two stories, and bedrooms are located downstairs. As I sleep at night, I often hear sound of rodents running around and scratching wood floor upstairs. The other day I think I found the gap where rodents can get into our condo. As shown in the picture, there are gaps between carpet and dry wall along the stairs, and gaps look pretty big for rodents to get in (but I am still not sure if this is the case).

If this seems like where the rodent can get into our condo, what would be a fix here? How can I block or seal this gap completely?

Thanks!