Measuring Spin

One of the holy grails in physics is the measurement of spin. There are many manifestations of spin-dependent phenomena such as spin dependent scattering, spin-orbit scattering inter alia. But all of the known experiments to measure spin or its consequences can only determine whether the spin is aligned parallel or anti-parallel to the quantisation axis as in the original Stern-Gerlach experiment. Indeed many theories of spin-dependent effects only calculate the consequences in these two spin states. However, much of time, the spins are not in well-defined states but in a mixture of the two. The relationship between a spin current, the spin and the resultant charge current induced by the Spin Hall Effect is given by the vector cross product. We, and others, have demonstrated the validity of this relationship in a variety of experiments where spin currents have been generated by spin-polarised injection into normal metals as well as magnon-spin-current conversion via spin pumping. By careful design of spin current circuits we will use this relationship to determine the angular dependence of spin as it is either deliberately disturbed by external fields or is naturally dephased by interaction with the environment. If this experiment were to succeed, it would offer solutions to problems such as the determination of the extent of quantum entanglement of spins - currently a very pressing problem in quantum physics and quantum information. Although this aim of the project has an element of adventurous risk associated with it, this is mitigated by the route we will pursue. We shall work in the broad area of spin current generation and detection using our world class materials such as Yttrium Iron Garnet. We shall combine materials such as antiferromagnets in symmetry breaking structures where we can control the Rashba field to manipulate spins- these experiments will guarantee high impact publications. In addition the work will involve a vast array of growth and characterisation techniques at the leading edge of physics. The involvement of NPL is critical in this project. Dr O Kazakova is a principal scientist in the Quantum Detection Group and has expertise in transport, nanomagnetism and 2d materials including graphene. The laboratories at NPL also offer many complementary techniques that will be essential to the success of the project such as advanced scanning probes. Thus this is a project that offers the highest levels of training, challenge and opportunity that are commensurate with the achievements and the ability of Ms Moran