Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Valley interference and spin exchange at the atomic scale in silicon   Tunneling is a fundamental quantum process with no classical equivalent,
which can compete with Coulomb interactions to give rise to complex phenomena.
Phosphorus dopants in silicon can be placed with atomic precision to address
the different regimes arising from this competition. However, they exploit
wavefunctions relying on crystal band symmetries, which tunneling interactions
are inherently sensitive to. Here we directly image lattice-aperiodic valley
interference between coupled atoms in silicon using scanning tunneling
microscopy. Our atomistic analysis unveils the role of envelope anisotropy,
valley interference and dopant placement on the Heisenberg spin exchange
interaction. We find that the exchange can become immune to valley interference
by engineering in-plane dopant placement along specific crystallographic
directions. A vacuum-like behaviour is recovered, where the exchange is
maximised to the overlap between the donor orbitals, and pair-to-pair
variations limited to a factor of less than 10 considering the accuracy in
dopant positioning. This robustness remains over a large range of distances,
from the strongly Coulomb interacting regime relevant for high-fidelity quantum
computation to strongly coupled donor arrays of interest for quantum simulation
in silicon.

30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs