Late Wednesday, the Korean Exchange warned investors about speculative trading in superconductor-related stocks following claims of a technological breakthrough that could revolutionize the energy industry. On Thursday, small-cap stocks such as Duksung Co. and Sunam Co. surged as much as their 30% daily limits for their third consecutive session. Sunam has jumped 220% in the last eight sessions, while Duksung has increased 165%. Mobiis Co. and Shinsung Delta Tech Co. have risen by 125% and 107%, respectively. Because of the volatility, the…