2023/06/25 by Keita Kishigi, Kishigi, Keita, Keita Tsukidashi +3
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Graphene research and applications #Materials Science (cond-mat.mtrl-sci) #Quantum many-body systems #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.2306.14128
openalex publication_date 2023/06/25 · openalex created_date 2023/06/28 · openalex updated_date 2026/07/28
Dirac points in two-dimensional massless Dirac fermions are topologically protected. Although single Dirac point cannot disappear solely, a pair of two Dirac points annihilates after merging at a time-reversal invariant momentum (TRIM). This process triggers a topological phase transition. In this paper, we numerically calculate the electronic specific heat (C) of the systems with a honeycomb lattice and α-(BEDT-TTF)2I3 in the case that two Dirac points are moving and merging by changing the ratio of the magnitude between the transfer integrals, which can be controlled by uniaxial pressure for example. When two Dirac points are close to but not at TRIM, the temperature dependence exhibits a crossover from C∝ T2.0 (expected for separated Dirac points) at low temperatures (T≤ T\rm co) to C∝ T1.5 (expected in the case of the merged Dirac points) at high temperatures (T≥ T\rm co). Here, T\rm co denotes the crossover temperature, which is determined by the potential barrier magnitude between two Dirac points. Our findings demonstrate that the precursor of the topological phase transition is observed through the temperature-dependence of the electronic specific heat.