Very Large Phonon‐Drag Thermoelectric Power of HgTe in Strong Magnetic Fields

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Abstract
The magneto‐Seebeck effect of almost intrinsic HgTe is investigated up to 96 kOe in the temperature range 20 to 120 K. The thermoelectric power in strong transverse magnetic fields. α⟂, is positive because the contribution of high mobility electrons is suppressed. Below about 50 K, α⟂ at 96 kOe increases rapidly with decreasing temperature and shows a prominent peak. The peak value of α⟂ of a typical sample reaches about 2 mV/K around 25 K. The dominant part of the observed value comes from the phonon‐drag effect of holes with large effective mass. The observed phonon‐drag contribution is one order of magnitude larger than that of heavily doped p‐type samples which were investigated previously. Such a large value is attributed to a substantially reduced hole—phonon scattering in the phonon relaxation mechanism of the almost intrinsic sample. According to an analysis using a model of phonon relaxation through three‐phonon processes discussed by Whitsett and Nelson, the dilation deformation potential constant of the Γ8‐band is determined as a equals; +3.8 eV using a shear deformation potential constant of b equals; −1.5 eV.

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