Macroscopic ground-state degeneracy and magnetocaloric effect in the exactly solvable spin-1/2 Ising–Heisenberg double-tetrahedral chain

Abstract

The ground-state degeneracy and magnetocaloric effect in the spin-1/2 Ising-Heisenberg double-tetrahedral chain are exactly investigated. It is demonstrated that the zero-temperature phase diagram involves two classical and two quantum chiral phases with distinct degrees of the macroscopic degeneracy. Different macroscopic degeneracies observed in the latter phases and at individual ground-state phase transitions are confirmed by multiple-peak dependencies of the specific heat and entropy on the magnetic field. The cooling capability of the model is well illustrated by the magnetic-field variations of the isothermal entropy change, temperature isotherms and the magnetic Grüneisen parameter.

Pairwise Entanglement in Double-Tetrahedral Chain with Different Landé g-Factors of the Ising and Heisenberg Spins

“…In this section, we will discuss the quantum entanglement in the spin-1/2 Ising-Heisenberg tetrahedral chain with the easy-plane Heisenberg interaction (we set ∆ = 2 for simplicity) and the antiferromagnetic Ising interaction J I > 0. According to the previous results [5,6,7], this particular version of the model exhibits the most intriguing quantum features. For simplicity, we will consider the Landé g-factors g I = 6 and g H = 2 for the Ising and Heisenberg spins, which coincide with real gyromagnetic ratios for Co 2+ and Cu 2+ ions, respectively.…”

“…In this paper, we will examine the quantum entanglement in the frustrated spin-1/2 Ising-Heisenberg double-tetrahedral chain with different Landé g-factors of the Ising and Heisenberg spins. The model was originally proposed and resolved by V. Ohanyan et al [5,6], and recently re-examined in context of the magnetocaloric effect [7]. Following the previous findings, the goal of this paper is to investigate how the spin chirality and the applied longitudinal magnetic field affect on an intensity of the pairwise entanglement in the model at zero and finite temperatures.…”

“…As demonstrated in Refs. [5,7], the considered quantum chain belongs to lattice-statistical models with exact closed-form solution for the partition function and basic thermodynamic quantities. Some of them, namely the sublattice magnetization…”

Peculiarities in pseudo-transitions of a mixed spin-(1/2, 1) Ising–Heisenberg double-tetrahedral chain in an external magnetic field

“…For instance, the pseudo-transitions were detected in the spin-1/2 Ising-Heisenberg diamond chain [9,10], two-leg ladder [11], as well as triangular tube [12]. Similarly, the emergence of pseudo-transitions was verified in the spin-1/2 Ising diamond chain [13] and the coupled spinelectron double-tetrahedral chain [14][15][16]. In general, the first derivatives of the free energy such as entropy, inter-nal energy or magnetization show a steep change around pseudo-critical temperature.…”

Avoiding the Obstacles in the Robot Working Zone by Using the Lee Algorithm

“…For the configuration field creation, it is necessary to display this obstacle in the xy plane. The configuration field is created as the dependence upon the rotation (parameter) q 2 from the rotation (parameter) q 1 , the values of the both rotations are necessary for its creation [5,10]. The q 1 and q 2 values can be acquired by using the final formulas of the two pairs of the inverse task solution, see Figure 2.…”