When investors think of surging artificial intelligence (AI) stocks, Palantir Technologies and Nvidia are probably the first two that come to mind. Palantir is a leader in AI software and its stock is up by a whopping 530% over the last 12 months. Nvidia supplies the world's best AI data center chips and its stock has climbed by 74% over the same period. But more and more companies are using AI to supercharge their legacy businesses. Duolingo (DUOL -5.27%), for instance, operates the world's largest digital ...