Two-temperature scales in the triangular-lattice Heisenberg antiferromagnet

Chen, Lei; Qu, Dai-Wei; Li, Han; Chen, Bin-Bin; Gong, Shou-Shu; Delft, Jan von; Weichselbaum, Andreas und Li, Wei (2019): Two-temperature scales in the triangular-lattice Heisenberg antiferromagnet. In: Physical Review B, Bd. 99, Nr. 14, 140404

Abstract

The anomalous thermodynamic properties of the paradigmatic frustrated spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLH) has remained an open topic of research over decades, both experimentally and theoretically. Here, we further the theoretical understanding based on the recently developed, powerful exponential tensor renormalization group method on cylinders and stripes in a quasi-one-dimensional (1D) setup, as well as a tensor product operator approach directly in 2D. The observed thermal properties of the TLH are in excellent agreement with two recent experimental measurements on the virtually ideal TLH material Ba8CoNb6O24. Remarkably, our numerical simulations reveal two crossover temperature scales, at T-l/J similar to 0.20 and T-h/J similar to 0.55, with J the Heisenberg exchange coupling, which are also confirmed by a more careful inspection of the experimental data. We propose that in the intermediate regime between the low-temperature scale T-l and the higher one T-h, the "rotonlike" excitations are activated with a strong chiral component and a large contribution to thermal entropies. Bearing remarkable resemblance to the renowned roton thermodynamics in liquid helium, these gapped excitations suppress the incipient 120 degrees order that emerges for temperatures below T-l.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Fakultätsübergreifende Einrichtungen: Center for NanoScience (CENS)
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik ; 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften
• ISSN: 2469-9950
• Sprache: Englisch