Staying or going? Chirality decides!

When an electronic device is cooled to low temperature, the wavelike nature of charge carriers becomes detectable through quantum interference effects. One example is weak localization, a small decrease in the conductivity of a disordered conductor [1, 2]. Since interference depends on the quantum-mechanical phase of electronic waves, the experimental signature of weak localization has been used over the last thirty years to probe the nature of charge carriers and disorder in numerous conducting materials [3, 4]. A new material to recently undergo such scrutiny is graphene [5], a oneatom-thick layer of carbon atoms. It has created a huge amount of interest, partly because electrons in it act like massless neutrinos. This behavior is manifest in a range of observed phenomena, including the integer quantum Hall effect [6–8], and it gave rise to the prediction of weak antilocalization in graphene [9], a small increase in the conductivity [2], rather than weak localization. So far, however, experiments have failed to clearly see this effect, reporting instead either weak localization or a suppression of it [10–13]. But now, writing in Physical Review Letters, F. V. Tikhonenko, A. A. Kozikov, A. K. Savchenko, and R. V. Gorbachev [14] at the University of Exeter, UK, demonstrate how to observe a transition from weak localization to antilocalization in graphene.