From Giant Magnetoresistance to Nonlinear Magnetoresistance in Quantum Materials – An Exciting Journey with Spin
Condensed Matter Theory Group, Materials Science Division, Argonne National Laboratory
Ever since its surprising emergence from relativistic quantum mechanics, spin has been known as an intrinsic angular momentum that plays a crucial role in electronic structure of matter. When the flows of spin and charge become intertwined through spin-orbit coupling or nontrivial magnetic structures, a host of intriguing magnetotransport phenomena emerge, such as giant magnetoresistance, spin Hall, topological Hall etc. In the first part of the talk, I will introduce a few basic concepts that are essential to understand the physics of these bulk transport phenomena. Then, I will review recent studies on a slew of linear magnetotransport phenonema originating from the interface of two materials with different electronic, magnetic or topological properties, which have no analogue in bulk materials due to the symmetry breaking at the interface. In the second part of the talk, I will introduce you to the emerging field of nonlinear transport in magnetic heterostructures and quantum materials, where strong spin-orbit interaction and broken symmetries conspire to give rise to remarkable nonlinear magnetotransport effects. As an example, I will show a novel bilinear magneto-electric resistance effect recently discovered in the surface states of topological insulators with robust spin-momentum locking protected by topology. Such nonlinear transport effects suggest potential applications of quantum materials in electronic and spintronic devices.