Nuclear Spin Relaxation Time Due to the Orbital Currents in Dirac Electron Systems

Hirosawa, Tomoki; Maebashi, Hideaki; Ogata, Masao

doi:10.7566/jpsj.86.063705

Cited by 15 publications

(28 citation statements)

References 25 publications

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“…The result of (1/T 1 ) orb has already been published in Ref. [11], but some errors there are corrected in this paper. We present a rigorous result of (1/T 1 ) orb for the 3D Dirac electrons, which correctly reproduces the two limiting cases of the free-electron gas and Weyl fermions, and give a prediction on (1/T 1 ) orb for quasi-2D Dirac electrons.…”

Section: Introductionmentioning

confidence: 94%

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

Maebashi

Hirosawa

Ogata

et al. 2019

Journal of Physics and Chemistry of Solids

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We study the nuclear magnetic relaxation rate and Knight shift in the presence of the orbital and quadrupole interactions for three-dimensional Dirac electron systems (e.g., bismuth-antimony alloys). By using recent results of the dynamic magnetic susceptibility and permittivity, we obtain rigorous results of the relaxation rates (1/T 1 ) orb and (1/T 1 ) Q , which are due to the orbital and quadrupole interactions, respectively, and show that (1/T 1 ) Q gives a negligible contribution compared with (1/T 1 ) orb . It is found that (1/T 1 ) orb exhibits anomalous dependences on temperature T and chemical potential µ. When µ is inside the band gap, (1/T 1 ) orb ∼ T 3 log(2T/ω 0 ) for temperatures above the band gap, where ω 0 is the nuclear Larmor frequency. When µ lies in the conduction or valence bands, (1/T 1 ) orb ∝ T k 2 F log(2|v F |k F /ω 0 ) for low temperatures, where k F and v F are the Fermi momentum and Fermi velocity, respectively. The Knight shift K orb due to the orbital interaction also shows anomalous dependences on T and µ. It is shown that K orb is negative and its magnitude significantly increases with decreasing temperature when µ is located in the band gap. Because the anomalous dependences in K orb is caused by the interband particle-hole excitations across the small band gap while (1/T 1 ) orb is governed by the intraband excitations, the Korringa relation does not hold in the Dirac electron systems.

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Section: Introductionmentioning

confidence: 94%

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

Maebashi

Hirosawa

Ogata

et al. 2019

Journal of Physics and Chemistry of Solids

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“…For a Weyl electron system without disorder, (T 1 T ) −1 ∝ T 2 log(2k B T / ω 0 ) with ω 0 denoting the nuclear Larmor frequency [19,20,28]. In Eq.…”

Section: Weak Disordermentioning

confidence: 99%

“…Recently, it was shown to be counterpart of the inverse of the charge renormalization factor in quantum electrodynamics [28]. Furthermore, (T 1 T ) −1 in Dirac electron systems was found to be proportional to T 2 due to the orbital effect when temperature is higher than the band gap [20]. This finding partly explains the temperature dependence of 1/T 1 observed in the β-detected NMR experiment on Bi 0.9 Sb 0.1 [29].…”

Section: Introductionmentioning

confidence: 99%

Nuclear spin relaxation rate near the disorder-driven quantum critical point in Weyl fermion systems

2020

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Disorder such as impurities and dislocations in Weyl semimetals (SMs) drives a quantum critical point (QCP) where the density of states at the Weyl point gains a non-zero value. Near the QCP, the asymptotic low energy singularities of physical quantities are controlled by the critical exponents ν and z. The nuclear spin-lattice relaxation rate, which originates from the hyperfine coupling between a nuclear spin and long-range orbital currents in Weyl fermion systems, shows intriguing critical behavior. Based on the self-consistent Born approximation for impurities, we study the nuclear spin-lattice relaxation rate 1/T1 due to the orbital currents in disordered Weyl SMs. We find that (T1T ) −1 ∼ E 2/z at the QCP where E is the maximum of temperature T and chemical potential µ(T ) relative to the Weyl point. This scaling behavior of (T1T ) −1 is also confirmed by the self-consistent T -matrix approximation, where a remarkable temperature dependence of µ(T ) could play an important role. We hope these results of (T1T ) −1 will serve as an impetus for exploration of the disorder-driven quantum criticality in Weyl materials.

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“…Recently, this approach was generaralized to the case of massive Dirac-like electrons in 3D, appropriate to semimetallic Bi 1x Sb x . 99,103 They find T-linear relaxation when the chemical potential is outside the gap, 99 but within the gap, an anomalous relation that is explicitly field dependent via the NMR frequency ω 0 is obtained, where λ orb ∝ T 3 ln(2k B T/ ω 0 ). While this is not what we find, it does suggest that if orbital relaxation is effective here, it may exhibit some unexpected field dependence in the inhomogeneous metallic state hypothesized for the tetradymites.…”

Section: B Low Temperature Electronic Propertiesmentioning

confidence: 99%

Ionic and electronic properties of the topological insulator Bi2Te2Se investigated via β -detected nuclear magnetic relaxation and resonance of
McFadden
¹
,
Chatzichristos
²
,
Chow
³

et al. 2019
Phys. Rev. B
11
0
6
0
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We report measurements on the high temperature ionic and low temperature electronic properties of the 3D topological insulator Bi 2 Te 2 Se using ion-implanted 8 Li β-detected nuclear magnetic relaxation and resonance. With implantation energies in the range 5-28 keV, the probes penetrate beyond the expected range of the topological surface state, but are still within 250 nm of the surface. At temperatures above ∼150 K, spin-lattice relaxation measurements reveal isolated 8 Li + diffusion with an activation energy E A = 0.185(8) eV and attempt frequency τ −1 0 = 8(3) × 10 11 s −1 for atomic site-to-site hopping. At lower temperature, we find a linear Korringa-like relaxation mechanism with a field dependent slope and intercept, which is accompanied by an anomalous field dependence to the resonance shift. We suggest that these may be related to a strong contribution from orbital currents or the magnetic freezeout of charge carriers in this heavily compensated semiconductor, but that conventional theories are unable to account for the extent of the field dependence. Conventional NMR of the stable host nuclei may help elucidate their origin. arXiv:1810.07879v3 [cond-mat.mtrl-sci]

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Nuclear Spin Relaxation Time Due to the Orbital Currents in Dirac Electron Systems

Cited by 15 publications

References 25 publications

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

Nuclear spin relaxation rate near the disorder-driven quantum critical point in Weyl fermion systems

Ionic and electronic properties of the topological insulator Bi2Te2Se investigated via β -detected nuclear magnetic relaxation and resonance of
McFadden
¹
,
Chatzichristos
²
,
Chow
³

et al. 2019
Phys. Rev. B
11
0
6
0
View full text Add to dashboard Cite

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Nuclear Spin Relaxation Time Due to the Orbital Currents in Dirac Electron Systems

Cited by 15 publications

References 25 publications

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

Nuclear spin relaxation rate near the disorder-driven quantum critical point in Weyl fermion systems

Ionic and electronic properties of the topological insulator Bi2Te2Se investigated via β -detected nuclear magnetic relaxation and resonance of McFadden1, Chatzichristos2, Chow3 et al. 2019Phys. Rev. B11060View full textAdd to dashboardCite

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Ionic and electronic properties of the topological insulator Bi2Te2Se investigated via β -detected nuclear magnetic relaxation and resonance of
McFadden
¹
,
Chatzichristos
²
,
Chow
³

et al. 2019
Phys. Rev. B
11
0
6
0
View full text Add to dashboard Cite