Large, nonsaturating thermopower in a quantizing magnetic field

Skinner, B. F.; Fu, Liang

doi:10.1126/sciadv.aat2621

Cited by 111 publications

(98 citation statements)

References 32 publications

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“…With this S xx is linear in the massless case consistently with Ref. 53, but in the massive case it increases quadratically. This is also consistent with the experimental result for massive Dirac electrons 29 where they found the thermopower to be linear, since the magnetic field is not high enough in the experiment to see the different behavior.…”

Section: Summary and Discussionsupporting

confidence: 74%

Thermoelectric transport coefficients of a Dirac electron gas in high magnetic fields

Könye

Ogata

2019

Phys. Rev. B

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We study the thermoelectric transport properties of a three-dimensional massive relativistic fermion gas with screened Coulomb impurities in high magnetic fields where only the lowest Landau levels contribute to the transport. Our results can be applied to experimental results of gapless and gapped Dirac materials. We focus on the effects of the mass term and we show the main differences that arise compared to the massless Dirac fermions. The different behavior is shown to be relevant at higher magnetic fields. The calculations are performed in the framework of the linear response theory using the exact quantum mechanical solution of the system in a constant magnetic field. We prove that the Mott formula and the Wiedemann-Franz law are valid at low temperatures and use them to calculate the thermoelectric transport coefficients. We show that the temperature range where the low temperature approximation is valid increases with increasing magnetic fields. The magnetic field dependence of measurable quantities (i.e. conductivity, Seebeck coefficient, Nernst coefficient and thermal conductivity) strongly depend on the magnetic field dependence of the scattering rate, thus the result relies on the proper treatment of the impurities. In this work they are included through the first Born approximation using screened charged impurities as impurity potential. We show that the electric conductivity does not change qualitatively in the case of finite mass term. On the other hand we find that the mass term causes significantly different behavior in the Seebeck and Nernst coefficients. arXiv:1909.11292v1 [cond-mat.mes-hall]

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Section: Summary and Discussionsupporting

confidence: 74%

Thermoelectric transport coefficients of a Dirac electron gas in high magnetic fields

Könye

Ogata

2019

Phys. Rev. B

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“…There is much recent interest in thermo-electricity of Weyl fermions in a Landau level [20][21][22][23], but that refers to currents perpendicular to B. Our findings show that charge renormalization in a Weyl superconductor provides a mechanism for a nonzero effect parallel to the field lines.…”

Section: Discussionmentioning

confidence: 76%

Effect of charge renormalization on the electric and thermoelectric transport along the vortex lattice of a Weyl superconductor

et al. 2019

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Building on the discovery that a Weyl superconductor in a magnetic field supports chiral Landau level motion along the vortex lines, we investigate its transport properties out of equilibrium. We show that the vortex lattice carries an electric current I = 1 2 (Q 2 eff /h)(Φ/Φ0)V between two normal metal contacts at voltage difference V , with Φ the magnetic flux through the system, Φ0 the superconducting flux quantum, and Q eff < e the renormalized charge of the Weyl fermions in the superconducting Landau level. Because the charge renormalization is energy dependent, a nonzero thermo-electric coefficient appears even in the absence of energy-dependent scattering processes.

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“…2f, for magnetic fields above 5.2 T, all electrons should occupy the lowest Landau band, i.e., the system is in the quantum limit. In the quantum limit, the thermopower of a Dirac/Weyl semimetal is expected to grow linearly and non-saturatingly with increasing magnetic field [34]. However, in our cases, −S xx exhibits an unexpected board peak above 5 T. In order to further elucidate the unusual thermoelectric response in the quantum limit, we increase the magnetic field up to 33 T. As shown in Fig.…”

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confidence: 74%

Anomalous Thermoelectric Effects of ZrTe5 in and beyond the Quantum Limit

et al. 2019

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Thermoelectric effects are more sensitive and promising probes to topological properties of emergent materials, but much less addressed compared to other physical properties. Zirconium pentatelluride (ZrTe5) has inspired active investigations recently because of its multiple topological nature. We study the thermoelectric effects of ZrTe5 in a magnetic field and find several anomalous behaviors. The Nernst response has a steplike profile near zero field when the charge carriers are electrons only, suggesting the anomalous Nernst effect arising from a nontrivial profile of Berry curvature. Both the thermopower and Nernst signal exhibit exotic peaks in the strong-field quantum limit. At higher magnetic fields, the Nernst signal has a sign reversal at a critical field where the thermopower approaches to zero. We propose that these anomalous behaviors can be attributed to the Landau index inversion, which is resulted from the competition of the √ B dependence of the Dirac-type Landau bands and linear-B dependence of the Zeeman energy (B is the magnetic field). Our understanding to the anomalous thermoelectric properties in ZrTe5 opens a new avenue for exploring Dirac physics in topological materials.Introduction-Transition-metal pentatellurides (ZrTe 5 , HfTe 5 ...) have attracted considerable interest as topological materials very close to the boundary of topological phase transition [1]. The negative longitudinal magnetoresistance [2, 3] and the linear energy-momentum dispersion demonstrated by the magnetoinfrared and optical spectroscopy measurements [4-7] implied a Dirac semimetal phase of ZrTe 5 . In contrast, scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy measurements detected a bulk band gap with topological edge states at side surfaces, giving the signatures of a weak 3D topological insulator (TI) [8][9][10]. Other spectroscopic studies favor the strong TI phase [11,12]. Recently, it was further proposed that these states can be tuned by temperature or pressure [12][13][14]. In addition to its nature of multiple topological phases, a moderate magnetic field is enough to drive this layered material into the quantum limit, in which all carriers occupy the lowest Landau band. This provides a platform to explore the exotic quantum phenomena caused by unique band topology in extremely strong magnetic fields. In particular, the magnetoresistance of ZrTe 5 decreases drastically when the field exceeds 8 T. Based on the picture of massless Dirac fermions, the sudden drop of magnetoresistance was conjectured to originate either from dynamical mass generation or topological phase transition from a 3D Weyl semimetal to a 2D massive Dirac metal [15,16]. Very recently, in ZrTe 5 the 3D quantum Hall effect was observed, which collapses into

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Large, nonsaturating thermopower in a quantizing magnetic field

Abstract: Applying a strong magnetic field to a Dirac or Weyl semimetal can produce record-large thermopower and figure of merit.

Cited by 111 publications

References 32 publications

Thermoelectric transport coefficients of a Dirac electron gas in high magnetic fields

Thermoelectric transport coefficients of a Dirac electron gas in high magnetic fields

Effect of charge renormalization on the electric and thermoelectric transport along the vortex lattice of a Weyl superconductor

Anomalous Thermoelectric Effects of ZrTe5 in and beyond the Quantum Limit

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