Frustrated honeycomb-lattice bilayer quantum antiferromagnet in a magnetic field

Abstract

Frustrated bilayer quantum magnets have attracted attention as flat-band spin systems with unconventional thermodynamic properties. We study the low-temperature properties of a frustrated honeycomb-lattice bilayer spin-1 2 isotropic (XXX) Heisenberg antiferromagnet in a magnetic field by means of an effective low-energy theory using exact diagonalizations and quantum Monte Carlo simulations. Our main focus is on the magnetization curve and the temperature dependence of the specific heat indicating a finite-temperature phase transition in high magnetic fields.

Ising versus Potts criticality in low-temperature magnetothermodynamics of a frustrated spin- 12 Heisenberg triangular bilayer

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] The frustrated spin- 1 2 Heisenberg square bilayer for instance displays a peculiar zero-field ground-state phase diagram including two lines of discontinuous and continuous phase transitions, which meet together at a peculiar quantum critical end point. 27 Moreover, the frustrated spin- 1 2 Heisenberg square [28][29][30][31][32] and honeycomb 33,34 bilayers belong to a valuable class of frustrated quantum spin systems, which exhibit a magnoncrystal state manifested in zero-and low-temperature magnetization curves as the last intermediate plateau emergent below the saturation field. The magnon-crystal phase is in its essence localized many-magnon eigenstate, which can be comprehensively described through a classical lattice-gas model or an equivalent Ising model within the framework of the localized-magnon approach (see Refs.…”