Unified phase diagram of antiferromagnetic SU(N) spin ladders

Weichselbaum, A.; Capponi, S.; Lecheminant, P.; Tsvelik, A. M. und Laeuchli, A. M. (2018): Unified phase diagram of antiferromagnetic SU(N) spin ladders. In: Physical Review B, Bd. 98, Nr. 8, 85104

Abstract

Motivated by near-term experiments with ultracold alkaline-earth atoms confined to optical lattices, we establish numerically and analytically the phase diagram of two-leg SU(N) spin ladders. Two-leg ladders provide a rich and highly nontrivial extension of the single chain case on the way towards the relatively little explored two-dimensional situation. Focusing on the experimentally relevant limit of one fermion per site, antiferromagnetic exchange interactions, and 2 <= N <= 6, we show that the phase diagrams as a function of the interchain (rung) to intrachain (leg) coupling ratio, J(perpendicular to)/J(parallel to), strongly differ for even versus odd N. For even N = 4 and 6, we demonstrate that the phase diagram consists of a single valence bond crystal (VBC) with a spatial period of N/2 rungs. For odd N = 3 and 5, we find surprisingly rich phase diagrams exhibiting three distinct phases. For weak rung coupling, we obtain a VBC with a spatial period of N rungs, whereas for strong coupling we obtain a critical phase related to the case of a single chain. In addition, we encounter intermediate phases for odd N, albeit of a different nature for N = 3 as compared to N = 5. For N = 3, we find a novel gapless intermediate phase with J(perpendicular to)-dependent incommensurate spatial fluctuations in a sizeable region of the phase diagram. For N = 5, there are strong indications for a narrow potentially gapped intermediate phase, whose nature is not entirely clear. Our results are based on (i) field theoretical techniques, (ii) qualitative symmetry considerations, and (iii) large-scale density matrix renormalization group (DMRG) simulations keeping beyond a million of states by fully exploiting and thus preserving the SU(N) symmetry.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 2469-9950
• Sprache: Englisch