Sensitive detection of magnetic fields has applications ranging from brain imaging to space exploration, and many technogologies have been developed for these many applications. Until now, all have been limited in sensitivity by the so-called "energy resolution limit," which constrains the combined spatial, temporal, and field resolution of the sensor. The in-practice limit was suspiciously close to hbar, the fundamental constant that defines the scale of the quantum world. In 2020 we analyzed the energy resolution limit (Mitchell et al. Rev. Mod. Phys. 2020), and concluded that exotic sensor types could beat this "limit."  In 2022 we employed a spinor Bose-Einstein condensate, to do just that, beating all previous sensors by almost two orders of magnitude, and more importantly showing that quantum physics does not place a hard limit on the sensitivity of field measurements (Palacios et al. PNAS 2022).

By stacking single atom layers of 2D materials one by one as if they were Lego pieces, heterostructures with atomically precise interfaces can be fabricated. Here, the pristine properties of each layer coexist with emerging interfacial quantum phenomena that is the focus of a rising field of research. For instance, controlling such interfaces with atomic precision can turn graphene bilayers into superconductors, or exciton superlattices. Adding layers of different properties basically at will also brings tunability of properties and multifunctionality that can be applied in optoelectronic, sensing or memory devices.

When moving to the two-dimensional analogues, however, controlling the lateral interfaces with atomic precision becomes a real challenge due to the stronger covalent bonding in this dimension.  As consequence, one cannot simply stack one-dimensional stripes laterally by existing fabrication techniques, and their bottom-up epitaxial growth becomes very limited and hard to bring to the nanoscale.

We have recently overcome this challenge by developing a bottom-up synthetic strategy where, in a kind of Lego chemistry, two type of molecular building blocks turn into an interdigitated array of two different graphene nanoribbon components forming atomically precise interfaces. For the first time, we demonstrate that not only the atomic, but also the electronic interface can be brought down to the single bond limit. The resulting interface also hosts nanometer scale heterogeneous pores, altogether expected to promote interesting phenomena such has the formation of interibbon exciton superlattices or an efficient photocatalytic splitting of water for hydrogen generation.