The Schottky-type specific heat as an indicator of relative degeneracy between ground and first-excited states: the case study of regular Ising polyhedra

TL;DR

This paper investigates how the Schottky-type specific heat in regular Ising polyhedra reveals the relative degeneracy between ground and first-excited states, especially near level-crossing fields, highlighting effects of geometric frustration.

Contribution

It demonstrates that the height and position of the Schottky maximum in specific heat depend on the degeneracy ratio of low-energy states in geometrically frustrated Ising clusters.

Findings

Double-peak specific heat near level-crossings

Schottky theory explains low-temperature peaks

Degeneracy differences influence peak characteristics

Abstract

The specific heat of regular Ising polyhedra is investigated in detail as a function of temperature and magnetic field. It is shown that the regular Ising polyhedra display diverse double-peak temperature dependences of the specific heat whenever the magnetic field approaches a level-crossing field. The Schottky theory of a two-level system often provides a plausible explanation of a height and position of low-temperature peak, which emerges in the specific heat of a regular Ising polyhedron due to low-lying excitations from a ground state to a first-excited state. The height and position of Schottky-type maximum depends essentially on a relative degeneracy of the ground state and first-excited state, which are in general quite distinct in geometrically frustrated Ising spin clusters. Low-temperature variations of the specific heat with the magnetic field exhibit multipeak structure with two peaks (of generally different height) symmetrically placed around each level-crossing field.