Quantum Theory of Thermomagnetic Phenomena in Metals and Semiconductors

Zyryanov, P. S.; Guseva, G. I.

doi:10.1070/pu1969v011n04abeh003767

Cited by 19 publications

(15 citation statements)

References 22 publications

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“…As estimated just above, the electron-particle collisions dominate over the magnetic-field-driven cyclic motion of electrons. Also, the quantizing energy of the magnetic field ħωC is substantially lower than the average thermal energy of the free electrons kBT, and the thermal motion completely smears the Landau sub-bands [49]. Therefore, those processes destroy the Landau sub-bands, and the magnetic field can hardly produce any remarkable influence on the inter-band excitation in the metals to increase absorption and improve laser-surface coupling [42,49].…”

Section: B Laser-surface Couplingmentioning

confidence: 99%

Fundamental mechanisms of nanosecond-laser-ablation enhancement by an axial magnetic field

2019

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Steady magnetic field perpendicular to laser beam is widely used to improve rate and quality of laser ablation. Recently we reported a 69-fold enhancement of laser ablation of silicon by magnetic field parallel to laser beam. To understand the fundamental mechanisms of that phenomenon, multi-pulse magnetic-field-enhanced ablation of stainless steel, titanium alloy, and silicon was performed. The influence of the magnetic field significantly varies depending on the material: from 2.8-fold ablation enhancement on stainless-steel and silicon to no pronounced ablation modification on titanium alloy. Those results are discussed in terms of magnetized-plasma, magneto-absorption, skin-layer, and magnetic-field-influenced transport effects. Understanding of those mechanisms is crucial for advanced controlling of nanosecond laser-surface coupling to improve laser micromachining.

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Section: B Laser-surface Couplingmentioning

confidence: 99%

Fundamental mechanisms of nanosecond-laser-ablation enhancement by an axial magnetic field

2019

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“…Clearly, some theoretical treatment of inelastic processes is needed -while it appears [17] that weak electron-electron interactions leave our result intact, phonon effects (e.g. drag) on the Nernst thermopower are less understood [20]. Careful direct measurements (or extractions) of α xy will be of great use as well.…”

Section: Methodsmentioning

confidence: 99%

“…5 in the semiclassical regime, with weak scattering and B → 0 -this regime may be realized in some semiconductors [20,21]. Rewriting Eq.…”

mentioning

confidence: 99%

Theory of Dissipationless Nernst Effects

Bergman

Oganesyan

2010

Phys. Rev. Lett.

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We develop a theory of transverse thermoelectric (Peltier) conductivity, αxy, in finite magnetic field -this particular conductivity is often the most important contribution to the Nernst thermopower. We demonstrate that αxy of a free electron gas can be expressed purely and exactly as the entropy per carrier irrespective of temperature (which agrees with seminal Hall bar result of Girvin and Jonson). In two dimensions we prove the universality of this result in the presence of disorder which allows explicit demonstration of a number features of interest to experiments on graphene and other two-dimensional materials. We also exploit this relationship in the low field regime and to analyze the rich singularity structure in αxy(B, T ) in three dimensions; we discuss its possible experimental implications. PACS numbers:The magnetothermoelectric Nernst-Ettingshausen effect [1] has enjoyed renewed interest in recent years, first as a probe of superconducting fluctuations, and more generally, as a novel transport characterization of electronic correlations. Following the initial work on the cuprates[2] strong magnetothermoelectricity was found in a variety of interesting materials. While precise theoretical treatment is lacking for most of these cases, phenomenological descriptions in terms of conventional weak-field quasiparticle transport theory [3,4,5,6] or effective classical hydrodynamic models [7,8] have been used with varied degree of success [9].In this letter we break from these earlier studies to treat finite field response directly, with no recourse to a low-field regime. Our chief accomplishment is the exact expression of the off-diagonal Peltier conductivity, α xy , in terms of entropy of free fermionic carriers (see Eqs. 5, 6, 7 and 10). In two dimensions we prove the universality of this expression (which also applies to Dirac fermions) in the presence of quenched disorder and compare it against available experimental data. In three dimensions we obtain, essentially in a closed form, the entire intricate singularity structure in α xy (as a function of magnetic field and temperature) inherited from the Landau level spectrum which bears strong resemblance to thermoelectric phenomenology of graphite [10]. We also examine the weak field limit, B → 0, where we predict a simple, α xy = −s/B, dependence on magnetic field and entropy density s. Quite generally, α xy is somewhat of a less studied and, hence, poorly understood quantity, at least as compared to electrical conductivity or entropy. Thus, our basic result directly linking α xy and entropy (importantly, without invoking the so called "entropy currents" used elsewhere in the literature [5,11]) is useful both for simplifying computations but also for developing intuition. Even if only approximate in more realistic models (e.g. with inelastic processes ignored by us here), it gives some credence to empirical associations of strong Nernst signatures with singular rearrangements of electronic structure, e.g. phase transitions. small thermal gradient is det...

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“…The early literature on thermomagnetic effects in degenerate semiconductors is summarized in reviews by Zyryanov and Guseva 1 and Puri and Geballe, 2 the latter dealing mainly with very low carrier density systems which can be taken into the high-field limit, i.e., only the last Landau level is occupied. The present work is concerned with the regime where many levels are occupied.…”

Section: Introductionmentioning

confidence: 99%

Magnetothermoelectric properties of the degenerate semiconductor HgSe:Fe

et al. 1996

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There are few previous data on the magnetothermoelectric properties of degenerate semiconductors. Although magnetic quantum oscillations in the thermopower have been previously studied, quantitative, or even semiquantitative agreement with theory was not achieved. We have developed a theoretical model allowing a quantitative description of both the oscillatory and nonoscillatory parts of the thermopower tensor S, and have studied its validity in an experimental system. For the experiments we have chosen a high mobility sample of HgSe:Fe (nϭ4.6ϫ10 24 m Ϫ3 ), and have measured both of the independent components of S in a transverse magnetic field B of р8 T at temperatures 1 KϽTϽ60 K, together with the longitudinal and Hall resistivities and the thermal conductivity. Our model predicts that the transverse component S yx is not affected by phonon drag, and all our data are in agreement with this. The absolute value of the nonoscillating part of S yx depends linearly on T consistent with domination by diffusion. We observe large oscillations in S yx which exhibit a phase shift of /2 relative to the resistivity oscillations. By including elastic electron scattering in the diffusion theory we obtain excellent quantitative agreement for both the oscillations and the smooth background under all conditions of B and T, including the observed phase shift of /2. In contrast to S yx , the longitudinal component S xx shows a large contribution from phonon drag over most of the temperature range. S xx exhibits quantum oscillations similar to S yx , but these are found to be in phase with those in the resistivity and are far too large to be explained by diffusion in any available model. Instead, they are well described by oscillations in electron-phonon scattering which modulates phonon drag in much the same way as is observed in twodimensional systems. Small oscillations are also observed in the lattice thermal conductivity and their magnitude is shown to be consistent with the same phonon-electron scattering being responsible. Our analysis demonstrates that the study of the thermopower is a powerful tool in the understanding of both the elastic ͑through S yx ) as well as the inelastic ͑through S xx ) scattering of electrons in degenerate semiconductors.

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Quantum Theory of Thermomagnetic Phenomena in Metals and Semiconductors

Cited by 19 publications

References 22 publications

Fundamental mechanisms of nanosecond-laser-ablation enhancement by an axial magnetic field

Fundamental mechanisms of nanosecond-laser-ablation enhancement by an axial magnetic field

Theory of Dissipationless Nernst Effects

Magnetothermoelectric properties of the degenerate semiconductor HgSe:Fe

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