Electronic correlations in a two-level dimer

Macedo, Lazaro A.; Lagos, Roberto E.

doi:10.1016/s0304-8853(00)01135-5

Cited by 1 publication

(1 citation statement)

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“…In the field of condensed matter Physics, specific heat measurements can be considered as a pivotal experimental technique for characterizing the fundamental excitations involved in a certain phase transition. Indeed, phase transitions involving spin 1,2 , charge 3 , lattice 4 (phonons) and orbital degrees of freedom, the interplay between ferromagnetism and superconductivity 5 , Schottky-like anomalies in doped compounds 6 , electronic levels in finite correlated systems 7 , among other features, can be captured by means of high-resolution calorimetry. Furthermore, the entropy change associated with a first-order phase transition, no matter its nature, can be directly obtained upon integrating the specific heat over T , i.e.…”

Section: Introductionmentioning

confidence: 99%

Specific Heat Anomalies in Solids Described by a Multilevel Model

Souza¹,

Paupitz²,

Seridonio³

et al. 2016

Braz J Phys

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Specific heat measurements constitute one of the most powerful experimental methods to probe fundamental excitations in solids. After the proposition of Einstein's model, more than one century ago (Annalen der Physik 22, 180 (1907)), several theoretical models have been proposed to describe experimental results. Here we report on a detailed analysis of the two-peak specific heat anomalies observed in several materials. Employing a simple multilevel model, varying the spacing between the energy levels ∆i = (Ei − E0) and the degeneracy of each energy level gi, we derive the required conditions for the appearance of such anomalies. Our findings indicate that a ratio of ∆2/∆1 ≈ 10 between the energy levels and a high degeneracy of one of the energy levels define the twopeaks regime in the specific heat. Our approach accurately matches recent experimental results. Furthermore, using a mean-field approach we calculate the specific heat of a degenerate Schottky-like system undergoing a ferromagnetic (FM) phase transition. Our results reveal that as the degeneracy is increased the Schottky maximum in the specific heat becomes narrow while the peak associated with the FM transition remains unaffected.

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