Energy band gap dependence of valley polarization of the hexagonal lattice

Kazu Ghalamkari, Yuki Tatsumi, Riichiro Saito

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


The origin of valley polarization of the hexagonal lattice is analytically discussed by tight binding method as a function of energy band gap. When the energy gap decreases to zero, the intensity of optical absorption becomes sharp as a function of k near the K (or KA) point in the hexagonal Brillouin zone, while the peak intensity at the K (or KA) point keeps constant with decreasing the energy gap. When the dipole vector as a function of k can have both real and imaginary parts that are perpendicular to each other in the k space, the valley polarization occurs. When the dipole vector has only real values by selecting a proper phase of wave functions, the valley polarization does not occur. The degree of the valley polarization may show a discrete change that can be relaxed to a continuous change of the degree of valley polarization when we consider the life time of photo-excited carrier.

Original languageEnglish
Article number024710
Journaljournal of the physical society of japan
Issue number2
Publication statusPublished - 2018

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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