Gapless to gapless phase transitions in quantum spin chains

Abstract

We investigate spin chains with bilinear-biquadratic (BLBQ) spin interactions as a function of an applied magnetic field $h$. At the Uimin-Lai-Sutherland (ULS) critical point we find a gapless to gapless transition revealed by the dynamical structure factor $S(q,\omega )$ as a function of $h$. At $h=0$, the envelope of the lowest energy excitations goes soft at {\it two points} $q_1=2\pi /3$ and $q_2=4\pi /3$, dubbed the phase A. With increasing field, the spectral peaks at each of the gapless points bifurcate, making in total {\it four} soft modes, and combine to form a new set of excitations that soften at a {\it single} point $q=\pi$ at $h_{c1}\approx 0.94$. Beyond $h_{c1}$ the system enters another gapless B-phase until the transition at $h_{c2}=4$ to the fully polarized phase. We compare the ULS model results with those for the AKLT model as a representative of gapped Haldane phase. We explain the mechanism of the gapless to gapless transition in the ULS model using its conserved charges and a spinon band picture. We also discuss the universality of central charges of the BLBQ family of models subjected to a magnetic field.

26 pages, 16 figures

References in corpus (7)

• Lieb-Robinson Bounds and the Exponential Clustering Theorem
• Spectral Functions with the Density Matrix Renormalization Group: Krylov-space Approach for Correction Vectors
• Lattice-Tuned Magnetism of Ru4+(4d4) Ions in Single-Crystals of the Layered Honeycomb Ruthenates: Li2RuO3 and Na2RuO3
• Effective magnetic interactions in spin-orbit coupled $d^4$ Mott insulators
• Scaling of entanglement entropy across Lifshitz transitions
• Unconventional magnetism in the 4d${}^4$ based ($S=1$) honeycomb system Ag${}_3$LiRu${}_2$O${}_6$
• Low-energy physics of isotropic spin-1 chains in the critical and Haldane phases

Cited by in corpus (8)

• Anyon dynamics in field-driven phases of the anisotropic Kitaev model
• Quantum phase transition between topologically distinct quantum critical points
• Quantum phase transitions and composite excitations of antiferromagnetic spin trimer chains in a magnetic field
• Dimensional reduction of Kitaev spin liquid at quantum criticality
• Machine learning reveals features of spinon Fermi surface
• Luther-Emery liquid and dominant singlet superconductivity in the hole-doped Haldane spin-1 chain
• Quantum criticality and emergent orders in the spin-1 bilinear-biquadratic-Kitaev chain
• Fermi surface as a quantum critical manifold: gaplessness, order parameter, and scaling in $d$-dimensions