Seminar "Resonating valence bond physics is not always governed by the shortest tunnelling loops" by Arnaud Ralko
Theory of Quantum Matter Unit would like to announce a seminar by Prof. Arnaud Ralko:
- Titile: Resonating valence bond physics is not always governed by the shortest tunnelling loops
- Speaker: Professor. Arnaud Ralko, Néel Institute, CNRS France.
- Date/Time: Thursday, October 22nd / 1:30-2:30pm
- Venue: C016, Lab1
Resonating valence bond physics is not always governed by the shortest tunnelling loops
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 (RVB). In this talk, I will show that the standard minimal truncation to the nearest-neighbor valence bond (NNVB) 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 (VBC), 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.
Arnaud Ralko & Ioannis Rousochatzakis, arxiv:1505.01819, soon in PRL.
We hope to see many of you at the venue.