Thermal difference reflectivity of tilted 2D Dirac materials

Deviation from perfect conical dispersion in Dirac materials, such as the presence of mass or tilting, enhances control and directionality of electronic transport. To identify these signatures, we analyze the thermal derivative spectra of optical reflectivity in doped massive tilted Dirac systems. The density of states and chemical potential are determined as preliminary steps to calculate the optical conductivity tensor at finite temperature using thermal convolution. Changes in reflection caused by temperature variations enable clear identification of critical frequencies in the optical response. By measuring these spectral features in the thermoderivative spectrum, energy gaps and band structure tilting can be determined. A comparison is presented between the spectra of various low-energy Dirac Hamiltonians. Our findings suggest that thermal difference spectroscopy holds promise as a valuable technique for probing interband transitions of 2D Dirac fermion

Valley-driven Zitterbewegung in Kekul\'e-distorted graphene

Graphene deposited on top of a Copper(111) substrate may develop a Y-shaped Kekul\'e bond texture (Kekul\'e-Y), locking the momentum of its Dirac fermions with its valley degree of freedom. As a consequence, the valley degeneracy of its band structure is broken, generating an energy dispersion with two nested Dirac cones with different Fermi velocities. In this work, we investigate the dynamics of electronic wave packets in the Kekul\'e-Y superlattice. We show that, as a result of the valley-momentum coupling, a valley-driven oscillatory motion of the wave packets ({\it Zitterbewegung}) could appear, but with a smaller frequency than the {\it Zitterbewegung} effect found pristine graphene. This makes Kekul\'e-Y graphene a compelling candidate for experimental observation of {\it Zitterbewegung} phenomenon in a two-dimensional system.Comment: 10 pages, 7 figure