Field-induced spin nematic Tomonaga-Luttinger liquid of the $S=1/2$ spin ladder system with the anisotropic ferromagnetic rung interaction

TL;DR

This paper investigates a spin-1/2 ladder system with anisotropic ferromagnetic rung interactions under magnetic field, revealing a field-induced spin nematic Tomonaga-Luttinger liquid phase characterized by two-magnon bound states, re-entrant transitions, and phase diagrams.

Contribution

It demonstrates the emergence of a spin nematic TLL phase in an unfrustrated, non-biquadratic system, expanding understanding of quantum spin liquids.

Findings

Identification of a nematic-spin-correlation-dominant TLL phase at high magnetic fields.

Observation of re-entrant phase transitions between two-magnon-bound and single-magnon TLL phases.

Presentation of phase diagrams illustrating the dependence on anisotropy, magnetization, and magnetic field.

Abstract

The $S=1/2$ quantum spin ladder system with the anisotropic ferromagnetic exchange interaction on the rung under magnetic field is investigated using the numerical diagonalization and the density matrix renormalization group (DMRG) analyses. It is found that the nematic-spin-correlation-dominant Tomonaga-Luttinger liquid (TLL) appears in some high magnetic field. It is included in the TLL phase where the two-magnon bound state is realized. For some suitable parameters, after the field-induced phase transition from this two-magnon-bound TLL phase to the single-magnon TLL one, the re-entrant transition to the two-magnon-bound TLL phase occurs, which is confirmed by the magnetization curves by the DMRG. Several phase diagrams on the plane of the coupling anisotropy versus the magnetization and the magnetic field are presented. The present result is a proposal of the candidate system which exhibits the spin nematic phase without the biquadratic interaction or the frustration.