Honeycomb Heisenberg Spin Ladder: Unusual Ground State and Thermodynamic Properties

TL;DR

This paper investigates the unique ground state and thermodynamic behaviors of a honeycomb spin ladder, revealing novel magnetic properties and phases distinct from traditional square ladders, supported by analytical, numerical, and experimental comparisons.

Contribution

It provides the first systematic analysis of the honeycomb spin ladder's ground state, phase diagram, and thermodynamic properties, highlighting features absent in square ladders.

Findings

Presence of a strong relevant term nJ and a half saturation magnetization plateau.

Identification of a unique ground state phase diagram.

Thermodynamic properties consistent with experimental data.

Abstract

The unusual ground state and thermodynamic properties of spin-1/2 two-leg honeycomb (HC) spin ladder are systematically studied by jointly utilizing various analytical and numerical methods. The HC spin ladder is found to exhibit behaviors dramatically different from those of the conventional square spin ladder. A strong relevant term nJ and a half saturation magnetization plateau that can be attributed to the formation of diluted dimer states are observed in the HC ladder, both of which are absent in the square ladder. The ground state phase diagram of the HC spin ladder is identified, and the thermodynamic properties of the specific heat and susceptibility for different couplings are thoroughly explored, where two kinds of excitations are unveiled. The distinct Wilson ratios for both spin ladders at the lower critical fields are also obtained. Our calculated result is well fitted to the experimental data of the two-leg HC spin ladder compound [Cu2L1(N3)4]n.