Thermopower, entropy, and the Mott relation in HgSe:Fe

Abstract

We have investigated the quantum oscillations in the diffusion thermopower of a HgSe crystal doped with about 1% Fe. The high concentration of Fe has provided sufficient attenuation of phonon-drag quantum oscillations to allow clear observation of oscillations in the diffusion thermopower of a degenerate semiconductor. At high magnetic fields the diffusion oscillations are well represented by the entropy per unit charge, though the measured amplitude is larger than expected by about 50%. At low fields the oscillations shift in phase and agree with those predicted from the electronic relaxation time using the Mott relation.

Thermoelectric quantum oscillations in ZrSiS

“…This confirms that the sign of the phase shift for S depends on the sign of the charge carriers. We do not observe any variation in the phase of the oscillations with the magnetic field, showing that S remains in the so-called Mott regime28. Making the usual assumption that SdH oscillations arise because changes in σ are proportional to oscillations in the density of states, then the total phase shift ϕ in the Lifshitz–Kosevich formula23 describing the SdH effect: cos[2 π ( F / B + ϕ )] is believed to be ± 1/2 and ± 5/8 for 2D and 3D parabolic bands, respectively (+ for holes and − for electrons)31.…”

“…Ali et al [13] on the basis of SdH measurements, since quantum oscillations in the diffusion thermoelectric power are shifted by ±𝜋/2 (or n= 0.25) in relation to SdH [25][26][27]. This, along with the fact that we do not observe any variation of the phase of the oscillations with the magnetic field, indicates that S remains in the so called Mott regime [27]. This 𝜋/2 phase shift arises because the diffusion thermoelectric power depends on how the electron or hole density of states changes with energy.…”

“… 13 from SdH measurements (see Supplementary Table 1 ), even though the measured values differ by 0.25. This is because quantum oscillations in the diffusion thermoelectric power are shifted by π /2 (or δn =1/4) in relation to SdH 25 26 27 28 , which means that the equivalent phase shift expected for SdH is given by ϕ=ϕ S ±1/4. This π /2 phase shift arises because the diffusion thermoelectric power depends on how the electron or hole density of states changes with energy.…”

Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering

“…The validity of the MR has been tested experimentally for many decades in various materials, such as doped semiconductors [3], nanotubes [4], nanowires [5][6][7], graphene [8,9], and topological insulators [10]. The technique of tuning the carrier density by electric field effect is particularly useful for examining the MR, since it allows a quantitative comparison between the thermoelectric power (TEP) and electrical conductivity at varying chemical potentials [4][5][6][7][8][9][10][11].…”

Thermoelectric power quantum oscillations in the ferromagnet UGe$_2$

“…Both contributions can contribute to the oscillatory part of the thermoelectric power under magnetic field. 7 In the present article we discuss the thermoelectric power in the ferromagnet UGe 2 with the main focus on the analysis of the observed quantum oscillations. UGe 2 has gained special attention as pressure induced superconductivity coexists with the ferromagnetic order below the critical pressure p c = 1.5 GPa where the ferromagnetism is suppressed 8 .…”