Ground-state and magnetocaloric properties of a coupled spin–electron double-tetrahedral chain (exact study at the half filling)

Abstract

Ground-state and magnetocaloric properties of a double-tetrahedral chain, in which nodal lattice sites occupied by the localized Ising spins regularly alternate with triangular clusters half filled with mobile electrons, are exactly investigated by using the transfer-matrix method in combination with the construction of the Nth tensor power of the discrete Fourier transformation. It is shown that the ground state of the model is formed by two non-chiral phases with the zero residual entropy and two chiral phases with the finite residual entropy S = Nk B ln 2. Depending on the character of the exchange interaction between the localized Ising spins and mobile electrons, one or three magnetization plateaus can be observed in the magnetization process. Their heights basically depend on the values of Landé g-factors of the Ising spins and mobile electrons. It is also evidenced that the system exhibits both the conventional and inverse magnetocaloric effect depending on values of the applied magnetic field and temperature.

Magnetization plateau as a result of the uniform and gradual electron doping in a coupled spin-electron double-tetrahedral chain

“…The magnetic structure of this 1D lattice is experimentally realized in the copper-based polymeric chain Cu 3 Mo 2 O 9 [52][53][54][55]. As has been shown in our recent works [56][57][58][59], the mixed spin-electron system with the lattice topology of the double-tetrahedral chain represents an excellent prototype model, which allows the exact investigation of many interesting physical phenomena such as quantum non-chiral and/or uncommon chiral ground states, the rational magnetization plateau, the abnormally narrow and high low-temperature peak of the specific heat and very abrupt (almost discontinuous) thermal variations of the entropy and sublattice magnetization caused by a difference in ground-state degeneracies, as well as the enhanced magnetocaloric effect. The main purpose of this paper is to explore in detail an effect of the uniform and gradual electron doping on the ground-state properties of the model and the plateau creation in the magnetization process in order to provide a deeper insight into doping-dependent magnetization plateaux.…”

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

“…Before concluding the subsection, it is noteworthy that the degeneracies of the classical F phase and the frustrated CHA phase were not discussed in the original works [18,19], because their omission did not affect presented results. On the other hand, the both ones, as well as the field-independent chirality of triangular clusters present in CHF and CHA phases, have been analyzed in detail in our recent works [40,41], which deal with the hybrid spin-electron double-tetrahedral chain. Moreover, the macroscopic degeneracies W = 2 N and 3 N observed at the phase transitions F-S and CHA-F, CHF-S, respectively, have also been confirmed at the field-induced ground-state phase transitions of the same kind in the latter work [41].…”

On the ground-state degeneracy and entropy in a double-tetrahedral chain formed by the localized Ising spins and mobile electrons

“…1). As recently shown [5][6][7], this hybrid model provides an excellent prototype, which allows a rigorous study of the macroscopic degeneracy at absolute zero temperature, the associated residual entropy, as well as other thermodynamic quantities. Another important stimulus for investigating the aforementioned model relates to the copper-based polymeric compound Cu 3 Mo 2 O 9 [13,14], which represents the experimental realizations of the doubletetrahedral chain structure.…”