Probing Fermi surface shifts with spin resolved transverse magnetic focussing

Transverse magnetic focussing is the solid state equivalent of a mass spectrometer. It is unique among 2D measurement techniques as it is able to measure a well defined section of the Fermi surface, making it possible to detect changes that would be averaged out over the whole Fermi surface. Here, we utilise this unique property to probe non-adiabatic spin dynamics and spin dependent scattering of holes. We combine spin-resolved magnetic focussing with an additional independent in-plane magnetic field and observe a change in focussing peak amplitude that is not symmetric with respect to the field direction (i.e. $+B_{\parallel} \neq -B_{\parallel}$), and is extremely sensitive to the magnitude of the in-plane magnetic field. We show that the magnetic focussing signal is extremely sensitive to small changes in the Fermi velocity, which can be used to detect small shifts in the Fermi surface caused by an in-plane magnetic field. We also find that focussing can be used to detect the proximity between spin-split Fermi surfaces, which cause non-adiabatic spin dynamics

State of nature

For the first time ever, the UK’s wildlife organisations have joined forces to undertake a health check of nature in the UK and its Overseas Territories. 60% of the 3,148 UK species we assessed have declined over the last 50 years and 31% have declined strongly. Half of the species assessed have shown strong changes in their numbers or range, indicating that recent environmental changes are having a dramatic impact on nature in the UK. Species with specific habitat requirements seem to be faring worse than generalist species. A new Watchlist Indicator, developed to measure how conservation priority species are faring, shows that their overall numbers have declined by 77% in the last 40 years, with little sign of recovery. Of more than 6,000 species that have been assessed using modern Red List criteria, more than one in 10 are thought to be under threat of extinction in the UK. Our assessment looks back over 50 years at most, yet there were large declines in the UK’s wildlife prior to this, linked to habitat loss. The UK’s Overseas Territories hold a wealth of wildlife of huge international importance and over 90 of these species are at high risk of global extinction. There is a lack of knowledge on the trends of most of the UK’s species. As a result, we can report quantitative trends for only 5% of the 59,000 or so terrestrial and freshwater species in the UK, and for very few of the 8,500 marine species. Much needs to be done to improve our knowledge. What we do know about the state of the UK’s nature is often based upon the efforts of thousands of dedicated volunteer enthusiasts who contribute their time and expertise to monitoring schemes and species recording. The threats to the UK’s wildlife are many and varied, the most severe acting either to destroy valuable habitat or degrade the quality and value of what remains. Climate change is having an increasing impact on nature in the UK. Rising average temperatures are known to be driving range expansion in some species, but evidence for harmful impacts is also mounting. The full report is online: www.rspb.org.uk/stateofnature We should act to save nature both for its intrinsic value and for the benefits it brings to us that are essential to our wellbeing and prosperity. Targeted conservation has produced inspiring success stories and, with sufficient determination, resources and public support, we can turn the fortunes of our wildlife around. The State of Nature report serves to illustrate that with shared resolve and commitment we can save nature