< Image:> In the figure, we plot the enhancement of the power factor scaled by that for 3D materials as a function of the ratio of thermal de Broglie length Lambda to the confinement length L. The lines are theory for 1D and 2D and dots are experiments for several materials. It is clear that quantum enhancement occurs when the confinement length is smaller than thermal de Broglie length.

The theory of thermoelectricity for low dimensional semiconductors is recently updated by Nguyen et al (2016), 23 years after the publication by Hicks and Dresselhaus (1993). Since the Hicks-Dresselhaus paper published in 1993, the researchers have focused the low dimensional materials (2D or 1D) for searching the high thermoelectric material according to their theory of the confinement effect on 1D and 2D thermoelectricity, which was successful. However, we notice that some 1D nanowire or 2D materials do not show enhancement of the thermoelectric power even though the confinement length L is sufficiently small.
In the new paper by Nguyen, we pointed out that "thermal de Broglie wavelength" is an important parameter to the enhancement of thermoelectricity. Thermoelectric power is enhanced only when the confinement length is smaller than the thermal de Broglie wavelength. This theory gives a precise direction of the material research for better thermoelectric materials in the future.

Publication details:
Authors: Nguyen. T. Hung, A. R. T. Nugraha, E. H. Hasdeo, M. S. Dresselhaus, R. Saito
Title: Quantum Effects in the Thermoelectric Power Factor of Low-Dimensional Semiconductors
Journal: Phys. Rev. Lett.
DOI: 10.1103/PhysRevLett.117.036602
Embargo date: July 7^th 2016

Contact:
Prof. Riichiro Saito
Department of Physics, Tohoku University
Email: rsaito * flex.phys.tohoku.ac.jp
(Replace * with @）


Posted on：July 28, 2016