Resonating dimer–monomer liquid state in a magnetization plateau of a spin-$$\frac{1}{2}$$ kagome-strip Heisenberg chain

Abstract

Highly frustrated spin systems such as the kagome lattice are a treasure trove of new quantum states with large entanglements. Herein, we study the spin-$$\frac{1}{2}$$ 1 2 Heisenberg model on a kagome-strip chain, which is a one-dimensional kagome lattice, using the density matrix renormalization group method. Calculating the central charge and entanglement spectrum for the kagome-strip chain, we find a gapless spin liquid state with doubly degenerate entanglement spectra in a 1/5 magnetization plateau. We also obtain a gapless low-lying continuum in the dynamic spin structure calculated using the dynamical density matrix renormalization group method. We then propose a resonating dimer–monomer liquid state that meets these features.

Magnetic phase diagrams of the spin- 12 Heisenberg model on a kagome-strip chain: Emergence of a Haldane phase

“…In this paper, we construct magnetic phase diagrams under the magnetic field in the spin-1/2 KSC using the density matrix renormalization group (DMRG) method. We confirm that magnetization plateaus appear in the wide range of exchange parameters at M/M sat = 0, 3/10, 1/3, 2/5, 7/15, 3/5, and 4/5, in addition to the phase diagram at M/M sat = 1/5 reported elsewhere [14]. We find that one of the 3/5 plateau phases has a doubly degenerate entanglement spectrum and edge excitations, similar to the spin-1 Haldane chain.…”

“…In addition, the Heisenberg models describing frustrated quantum spin chains are known to exhibit various types of quantum phases, which have been studied intensively. Magnetization plateaus and strong quantum entanglement states due to the competition between frustration and quantum fluctuations have been found in the diamond chain [3][4][5], kagome-strip chains (KSCs) [6][7][8][9][10][11][12][13][14], and various frustrated one-dimensional chains [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

“…1, which has the lattice structure similar to the kagome lattice, exhibits magnetization plateaus at M/M sat = 0, 1/5, 3/10, 1/3, 2/5, 7/15, 3/5, and 4/5 [11]. One of the 1/5 plateau phases has features of both the half-integer spin and integer spin chains [14]. This implies that the KSC has strong frustration effects similar to the kagome lattice and strong quantum fluctuations inherent in one dimension unlike the two-dimensional kagome lattice.…”

“…However, except for M/M sat = 1/5, the magnetic phase diagrams of the KSC have not been completely determined. Therefore, there is a possibility of finding new phases that have not been found in previous studies [11,14]. Constructing complete magnetic phase diagram under the magnetic field will provide a strong motivation to experimentally investigate a model compound of the KSC reported before [41].…”

“…We find that one of the 3/5 plateau phases has a doubly degenerate entanglement spectrum and edge excitations, similar to the spin-1 Haldane chain. A phase with these characteristics has been identified at M/M sat = 1/5 [14]. Therefore, there is probability that these magnetization plateaus will be observed experimentally in the future using, for example, the model compound [41].…”