ABC...z Seminar Series: Thursday, November 15th: Crystal symmetry and spin-orbit torques in transition metal dichalcogenide / ferromagnet heterostructures

Event Date: 

Thursday, November 15, 2018 - 3:30pm

Event Date Details: 

Light refreshments served at 3:30 seminar begins at 3:45 and lasts one hour, including questions.

Event Location: 

  • 1601 Elings Hall
  • ABC...z Seminar Series

Materials with large spin-orbit coupling can convert a charge current into a spin current through mechanisms such as the spin Hall and Rashba-Edelstein effects. These spin-orbit generated spins can be used to exert a torque on an adjacent ferromagnet, and provide a highly efficient means of manipulating magnetic moments for memory applications. However, the spins generated by such spin-orbit effects are fundamentally limited by the symmetries of the spin-generating material. In most materials studied, the spin direction is required by symmetry to lie in the sample plane and perpendicular to an in-plane applied current, i.e., a Rashba-like symmetry. In this talk, I will show experimentally that the constraints on the spin-orbit generated spins can be reduced by using spin-source materials with low structural symmetries, such as the transition metal dichalcogenides WTe2 and 1T’-MoTe2. Specifically, I will discuss measurements of spin-orbit driven torques in WTe2/ferromagnet and 1T’-MoTe2/ferromagnet heterostructures down to the monolayer limit. I will describe the observation of novel torques beyond a typical Rashba-like symmetry, and show how those torques reflect the structural symmetries of the transition metal dichalcogenide crystals in a detailed way.  Finally, I will describe a pathway for improved switching efficiency in future magnetic memory technologies that leverages these results.

Greg Stiehl, Cornell University