Universal Thermoelectric Effect of Dirac Fermions in Graphene

We numerically study the thermoelectric and thermal transport in trilayer graphene with different stacking orders in the presence of interlayer bias under a strong perpendicular magnetic field. In biased ABA-stacked case, we find that the thermoelectric conductivity displays different asymptotic behaviors with the varying of the temperature, similar to that of monolayer graphene. In the high temperature regime, the transverse thermoelectric conductivity αxy saturates to a universal value 2.77kB e/h at the center of each LL, while it displays a linear temperature dependence at low temperatures limit. The calculated transverse thermal conductivity κxy exhibits two plateaus away from the band center. The transition between the two plateaus is continuous, which is accompanied by a pronounced peak in the longitudinal thermal conductivity κxx. In biased ABC-stacked case, it is found that both the thermoelectric conductivity and thermal conductivity have similar properties to the biased bilayer graphene, which is consistent with the behavior of a band insulator. The obtained results demonstrate the sensitivity of the thermoelectric conductivity to the band gap near the Dirac point. We also verify the validity of the Mott-relation and the generalized Wiedemann-Franz law.

supporting

confidence: 79%

Stacking-order dependence in thermoelectric transport of biased trilayer graphene

Sheng

Liu

2012

“…As seen from Fig.2(a) and (b), the transverse thermoelectric conductivity α xy displays a series of peaks, while the longitudinal thermoelectric conductivity α xx oscillates and changes sign at the center of each LL. These results exhibit quite different behavior compared to those of graphene 18 . Firstly, there is no LL near E F = 0 and the positions of all the peaks in α xy shift to both sides due to a finite g. The peak of α xy for the central (n = 0) LL appears at E F = 0.5ω 1 .…”

Section: Thermoelectric Transport Of 3dti Thin Filmmentioning

confidence: 46%

“…Owing to these rich phase diagram for the QHE, the 3DTI thin film is expected to exhibit novel thermoelectric transport properties. However, theoretical studies of the thermoelectric transport properties of 3DTI thin film are limited, compared with those of graphene systems 18,19 . In particular, a careful examination of the thermoelectric transport properties has not been done so far in the presence of g and ∆.…”

mentioning

confidence: 99%

Thermoelectric transport in thin films of three-dimensional topological insulators

Sheng

Liu

2013

We numerically study the thermoelectric transport properties based on the Haldane model of three-dimensional topological insulator (3DTI) thin film in the presence of an exchange field g and a hybridization gap ∆. The thermoelectric coefficients exhibit rich behaviors as a consequence of the interplay between g and ∆ in the 3DTI thin film. For ∆ = 0 but g = 0, the transverse thermoelectric conductivity αxy saturates to a universal value 1.38kB e/h at the center of each Landau level (LL) in the high temperature regime, and displays a linear temperature dependence at low temperatures. The semiclassical Mott relation is found to remain valid at low temperatures. If g = 0 but ∆ = 0, the thermoelectric coefficients are consistent with those of a band insulator. For both g = 0 and ∆ = 0, αxy saturates to a universal value 0.69kB e/h at the center of each LL in the high temperature regime. We attribute this behavior to the split of all the LLs, caused by the simultaneous presence of nonzero g and ∆, which lifts the degeneracies between Dirac surface states.

“…In addition, as could be seen from Figs. (6), (7) and (8), the chemical potential is usually not situated inside the gap, even though a gap opens for certain doping and external electric field. Both of these effects suppress the thermopower for biased multilayer graphene systems with N ≥3.…”

Section: Biased Multilayer Graphene: the Electronic Structurementioning

confidence: 99%

Thermopower of multilayer graphene

Hao

Lee

2010

We systematically calculate thermopower of biased and unbiased multilayer graphene systems. The effect of screening to a bias field perpendicular to the graphene planes is taken into account selfconsistently under the Hartree approximation. The model including nearest neighbor hopping and the more general Slonczewski-Weiss-McClure (SWMcC) model are both considered for a comparison. The effect of impurity scattering is studied for monolayer and unbiased bilayer graphene and is treated in terms of the self-consistent Born approximation. For a monolayer graphene, only when the effect of impurity scattering is taken into account, could all the qualitative aspects of the experimental results be correctly reproduced. Besides bilayer graphene, only trilayer graphene opens a small gap and shows a slight enhancement of thermopower under an external bias. The biased bilayer graphene shows the largest thermopower among all the systems studied.