Quantum phase transitions in alternating spin-($\frac{1}{2}$, $\frac{5}{2}$) Heisenberg chains

Abstract

The ground state spin-wave excitations and thermodynamic properties of two types of ferrimagnetic chains are investigated: the alternating spin-1/2 spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the spin-5/2 site. Results for magnetic susceptibility, magnetization and specific heat are obtained through the finite-temperature Lanczos method with the aim in describing available experimental data, as well as comparison with theoretical results from the semiclassical approximation and the low-temperature susceptibility expansion derived from Takahashi's modified spin-wave theory. In particular, we study in detail the temperature vs. magnetic field phase diagram of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases are identified: the Luttinger Liquid phase, the ferrimagnetic plateau and the fully polarized one, and the respective quantum critical points and crossover lines.

Topology of many-body edge and extended quantum states in an open spin chain: 1/3 plateau, Kosterlitz-Thouless transition, and Luttinger liquid

“…On the other hand, the low-energy theory of magnons in a gapped system under a magnetic field is that of a Lieb-Liniger [46] Bose fluid with δ-function interactions [47]. In addition, in the high dilute regime of magnons, the theory is equivalent to a Tonks-Girardeau [48] Bose system with a hard-core repulsion [47] or a fermionic system [30,47,49,50]. Thereby in the highdilute regime h → h − or h + , the low-energy magnon excitations from the 1/3-plateau have dispersion relations as in Eq.…”

The role of density-dependent magnon hopping and magnon-magnon repulsion in ferrimagnetic spin-(1/2, $S$) chains in a magnetic field

“…Furthermore, rich phase diagrams are observed through doping [46][47][48][49][50] or adding geometric frustration [51][52][53][54][55][56][57][58] to the ferrimagnetic models. In particular, ferrimagnetic spin-(1/2, S) chains under an applied magnetic field present magnetization plateaus at m = S − 1/2 (ferrimagnetic plateau) and m = S + 1/2 (saturation plateau), where m is the magnetization per unit cell [59][60][61][62][63][64]. On the experimental side, the onedimensional magnetic phase of a variety of bimetallic compounds was shown to be modeled by spin-(1/2, S) ferrimagnetic chains [65][66][67][68][69][70].…”

Magnetic-field–temperature phase diagram of alternating ferrimagnetic chains: Spin-wave theory from a fully polarized vacuum

“…The spin-wave theory 37 of ferrimagnetic chains [37][38][39][40][41][42][43][44][45] was developed from the classical ferrimagnetic ground state, considering free and interacting magnons, with emphasis on zero-field properties. The magnetization curves of these systems under an applied magnetic field were discussed mainly through numerical methods 38,42,[46][47][48][49][50][51] .…”