Electrical Manipulation of Spin Splitting Torque in Altermagnetic RuO2

Abstract: Due to nonrelativistic altermagnetic spin splitting effect (ASSE), altermagnets can generate time-reversal-odd spin current and spin splitting torque (SST) with spin polarization parallel to the N\'eel vector. Hence the effective manipulation of SST would provide plenty of opportunities for designable spintronic devices, which remains elusive. Here, the electrical control of SST is achieved in altermagnetic RuO2, based on controllable N\'eel vector of RuO2 and N\'eel vector-dependent generation of SST. We demonstrate the current-induced switching of N\'eel vector via spin-orbit torque in RuO2 films, according to the reversible polarity of electrical transport measurements and X-ray magnetic linear dichroism (XMLD). The XMLD also unprecedentedly demonstrates that N\'eel vector really exists in altermagnets. The switching of N\'eel vector to the current direction and resultantly enhanced spin polarization parallel to the N\'eel vector brings about stronger ASSE-induced spin current. Our findings not only enrich the properties of altermagnets but also pave the way for high speed memories and nano-oscillators with excellent controllability and efficiency.