title: Resonating-Valence-Bond Physics Is Not Always Governed by the Shortest Tunneling Loops.
abstract: It is well known that the low-energy sector of quantum spin liquids and other magnetically disordered systems is governed by short-ranged resonating-valence bonds. Here we show that the standard minimal truncation to the nearest-neighbor valence-bond basis fails completely even for systems where it should work the most, according to received wisdom. This paradigm shift is demonstrated for the quantum spin-1/2 square kagome, where strong geometric frustration, similar to the kagome, prevents magnetic ordering down to zero temperature. The shortest tunneling events bear the strongest longer-range singlet fluctuations, leading to amplitudes that do not drop exponentially with the length of the loop L, and to an unexpected loop-six valence-bond crystal, which is otherwise very high in energy at the minimal truncation level. The low-energy effective description gives in addition a clear example of correlated loop processes that depend not only on the type of the loop but also on its lattice embedding, a direct manifestation of the long-range nature of the virtual singlets.
authors.affiliation: Institut Néel, UPR2940, Université Grenoble Alpes et CNRS, Grenoble FR-38042, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Ralko
authors.affiliation: School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55116, USA.|Max Planck Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Rousochatzakis