Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Formation of orbital molecules on a pyrochlore lattice induced by A-O
  bond covalency   The pyrochlore ruthenate In$_2$Ru$_2$O$_7$ displays a subtle competition
between spin-orbital entanglement and molecular orbital formation. At room
temperature, a spin-orbit-entangled singlet state was identified. With
decreasing temperature, In$_2$Ru$_2$O$_7$ undergoes multiple structural
transitions and eventually forms a nonmagnetic ground state with semi-isolated
Ru$_2$O units on the pyrochlore lattice. The dominant hopping through the
Ru-O-Ru linkage leads to molecular orbital formation within the Ru$_2$O units.
This molecular orbital formation is unique in that it involves the O$^{2-}$
anions, unlike the transition-metal dimers observed in systems with
edge-sharing octahedra. We argue that the covalent character of In-O bonds
plays a pivotal role in the structural transitions and molecular orbital
formation and such bonding character of "$A$-site" ions is an important
ingredient for electronic phase competition in complex transition metal oxides.

13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex