Symmetry is a fascinating concept and ubiquitous in physics. But can we use symmetry concepts to inspire or engineer better nanodevices? In this borrel lecture I will give a brief introduction to basic symmetry concepts and show how these are useful for the development of spintronic and opto-spintronic devices using layered van der Waals materials. We will revise some of the symmetry implications for spin-dependent electronic states and understand why many thought that bulk van der Waals crystals were boring (spintronics wise). I will show that this is not the case, and that the layered structure is actually what allows for some opto-spintronic effects to occur. I will then show how the use of low crystal symmetry materials can give rise to opto-electronics, spintronic and thermoelectric effects which are not allowed in conventional systems. Using these low symmetry materials, we can make photodetectors which are highly sensitive to light polarisation, allowing us to replace bulky optical setups with a single nanodevice. Low symmetry semimetals can be used to electrically manipulate magnetisation at the nanoscale in a very promising way, particularly important for the development of new random-access memory (RAM) architectures. The same materials can also be used to develop thermoelectric diodes, for which the thermoelectric voltages are independent of the direction of the temperature gradient, particularly useful for heat recycling in computer chips. Throughout these examples I aim to illustrate that we can use the fundamental symmetry concepts to develop new applied nanodevices which can shape future technology.

ERO: Emily