Magnetothermoelectric effects in graphene and their dependence on scatterer concentration, magnetic field, and band gap

Abstract

Using a semiclassical Boltzmann transport equation (BTE) approach, we derive analytical expressions for electric and thermoelectric transport coefficients of graphene in the presence and absence of a magnetic field. Scattering due to acoustic phonons, charged impurities and vacancies are considered in the model. Seebeck (Sxx) and Nernst (N ) coefficients have been evaluated as functions of carrier density, temperature, scatterer concentration, magnetic field and induced band gap, and the results are compared with experimental data. Sxx is an odd function of Fermi energy while N is an even function, as observed in experiments. The peaks of both coefficients are found to increase with decreasing scatterer concentration and increasing temperature. Furthermore, opening a band gap decreases N but increases Sxx. Applying a magnetic field introduces an asymmetry in the variation of Sxx with Fermi energy across the Dirac point. The formalism is more accurate and computationally efficient than the conventional Green's function approach used to model transport coefficients and can be used to explore transport properties of other exotic materials.

Thermoelectric properties of the (an-)isotropic QGP in magnetic fields

“…Using the Onsager reciprocity relation of the thermoelectric and electric conductivity tensors in a magnetic field, σ x x,a (α x x,a ) = σ yy,a (α yy,a ) and σ xy,a (α xy,a ) = −σ yx,a (−α yx,a ), we finally derive the expressions of the Seebeck coefficient (S x x,a ) and the Nernst signal (N a ) for ath species from Eqs. ( 18) and ( 19) [86][87][88][89]…”

Enhancing Thermopower and Nernst Signal of High‐Mobility Dirac Carriers by Fermi Level Tuning in the Layered Magnet EuMnBi2

“…For Gd#4 located closest to the Dirac point, however, S yx max suddenly decreases to 24 µV K −1 , followed by the negligibly small S yx values (<1.5 µV K −1 ) in the entire temperature range for the electron‐doped samples (Figure 2f,g). For a simple 2D Dirac band, the calculation predicts that S yx is an even function of E F , showing a large positive peak at the Dirac point, [ 58,59 ] which cannot reproduce the observed electron‐hole asymmetric S yx . Considering that there are some less‐dispersive parabolic conduction bands just above E F = 0 (e.g., at the M point shown in Figure 1c), [ 48 ] the vanishingly small S yx for E F > 0 may be caused by the multi‐band effect.…”

Searching for a promising topological Dirac nodal-line semimetal by angle resolved photoemission spectroscopy

“…The electronic excitations around the band-crossing points in TSM can be analogous to the relativistic Weyl or Dirac fermions, making it an important platform to investigate fundamental high-energy physics in condensed matter systems [3]. Besides, owing to the outstanding electronic, optical, thermal and magnetic properties, TSM can be broadly applied in some important areas, such as topological quantum computation [4], photoelectric devices [5], thermoelectric [6] and magneto thermoelectric [7] applications, catalysis [8] and so on. Thus, the prediction [9,10], material preparation and characterization [11,12] of TSM have attracted much attentions in recent years.…”

“…In metal-semimetal-metal terahertz device, owing to the excitation of Dirac fermions, when the Dirac node is tuned to E F , it shows colossal photoresponse improvement at terahertz frequency, with a room-temperature photoresponsivity of 0.52 A W −1 at 0.12 THz and 0.45 A W −1 at 0.3 THz [5]. In magneto-thermoelectric application, Nernst coefficients increases progressively as E F approaches the Dirac point and reach the maximum when they matched, exhibiting an even function at series of carrier densities and temperatures [7]. In addition, some important chemistry reactions are favored when the Dirac point meet E F , such as Diels-Alder reaction [15].…”