Thermoelectric and optical probes for a Fermi surface topology change in noncentrosymmetric metals

Verma, Sankalp; Biswas, Tutul; Ghosh, Tarun Kanti

doi:10.1103/physrevb.100.045201

Cited by 13 publications

(9 citation statements)

References 73 publications

(90 reference statements)

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“…The energy-dependent relaxation times used for calculating spin currents in 3D non-centrosymmetric metals have the following forms [45]…”

Section: D Noncentrosymmetric Systemmentioning

confidence: 99%

Role of Berry curvature in the generation of spin currents in Rashba systems

Kapri,

Dey,

Ghosh

2021

Preprint

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We study the background (equilibrium), linear and nonlinear spin currents in 2D Rashba spinorbit coupled systems with Zeeman splitting and in 3D noncentrosymmetric metals using modified spin current operator by inclusion of the anomalous velocity. The linear spin Hall current arises due to the anomalous velocity of charge carriers induced by the Berry curvature. The nonlinear spin current occurs due to the band velocity and/or the anomalous velocity. For 2D Rashba systems, the background spin current saturates at high Fermi energy (independent of the Zeeman coupling), linear spin current exhibits a plateau at the 'Zeeman' gap and nonlinear spin currents are peaked at the gap edges. The magnitude of the nonlinear spin current peaks enhances with the strength of Zeeman interaction. The linear spin current is polarized out of plane, while the nonlinear ones are polarized in-plane. We witness pure anomalous nonlinear spin current with spin polarization along the direction of propagation. In 3D noncentrosymmetric metals, background and linear spin currents are monotonically increasing functions of Fermi energy, while nonlinear spin currents vary non-monotonically as a function of Fermi energy and are independent of the Berry curvature. These findings may provide useful information to manipulate spin currents in Rashba spin-orbit coupled systems.

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“…The energy-dependent relaxation times used for calculating spin currents in 3D non-centrosymmetric metals have the following forms [45]…”

Section: D Noncentrosymmetric Systemmentioning

confidence: 99%

Role of Berry curvature in the generation of spin currents in Rashba systems

Kapri,

Dey,

Ghosh

2021

Preprint

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“…Due to different Fermi surface topology of NCMs for ξ F > 0 and ξ F < 0, ∆ > and ∆ < show different behaviour with respect to the change in the carrier density. Note that ∆ > depends only on the carrier density, but ∆ < depends on both the carrier density and the Rashba energy ξ α 54 . This different behavior of width of interband PHC acts as a probe to observe the distinct Fermi surface topology of NCMs for Fermi energies below and above the BTP.…”

Section: Dynamical Polarization Functionmentioning

confidence: 99%

“…The peak outside the Rasbha continuum indicates the undamped plasmon mode for q = 0.01kα. For completeness, we also show the behavior of the real part of optical conductivity for non-interacting case (dashed curve) 54 . Parameters: Carrier density ne = 16nα (same as Fig.…”

Section: Plasmonsmentioning

confidence: 99%

“…It has been verified both theoretically and experimentally 34,35 that the system changes its behavior from paramagnetic to diamagnetic as Fermi energy sweeps across the BTP from below. There are also several studies in BiTeX compounds [36][37][38][39][40][41][42][43][44][45][46][47][48] and noncentrosymmetric metals [48][49][50][51][52][53][54] in the context of transport, magnetic, thermoelectric and optical response showing distinct behavior below and above the BTP due to change in the Fermi surface topology. All these electronic properties mainly based on the single particle excitations of the systems.…”

Section: Introductionmentioning

confidence: 99%

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Dynamical polarization and plasmons in noncentrosymmetric metals

Verma,

Kundu,

Ghosh

2020

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We study the dynamical polarization function and plasmon modes for spin-orbit coupled noncentrosymmetric metals such as Li2(Pd1−xPtx)3B. These systems have different Fermi surface topology for Fermi energies above and below the spin degenerate point which is also known as the band touching point (BTP). We calculate the exact dynamical polarization function numerically and also provide its analytical expression in the long wavelength limit. We obtain the plasmon dispersion within the framework of random phase approximation. In noncentrosymmetric metals, there is a finite energy gap in between intra and interband particle hole continuum for vanishing excitation wavevector. In the long wavelength limit, the width of interband particle hole continuum behaves differently for Fermi energies below and above the BTP as a clear signature of the Fermi surface topology change. We find a single undamped optical plasmon mode lying in between the intra and interband particle hole continuum for Fermi energies above and below the BTP within a range of parameters. The plasmon mode below the BTP has smaller velocity than that of above the BTP. It is interesting to find that as we tune the Fermi energy around the BTP, the plasmon mode becomes damped within a range of electron-electron interaction strength. For Fermi energies above and below the BTP, we also obtain an approximate analytical result of plasma frequency and plasmon dispersion which match well with their numerical counterparts in the long wavelength limit. The plasmon dispersion is ∝ q 2 with q being the wave vector for plasmon excitation in the long wavelength limit. We find that varying the carrier density with fixed electron-electron interaction strength or vice versa does not change the number of undamped plasmon mode, although damped plasmon modes can be more in number for some values of these parameters. We demonstrate our results by calculating the loss function and optical conductivity which can be measured in experiments.

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“…The broken IS also results in nontrivial Berry curvature (BC) 27 in the system. The electrical and thermoelectric transport properties of the system in the absence of magnetic field are not affected by BC and has been studied recently 28 . However, in the presence of weak magnetic field, the BC and orbital magnetic moment (OMM) produces significant modification in the transport properties which is the prime focus of our paper.…”

Section: Introductionmentioning

confidence: 99%

Berry curvature induced magnetotransport in 3D noncentrosymmetric metals

Pal,

Dey,

Ghosh

2021

Preprint

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We study the magnetoelectric and magnetothermal transport properties of noncentrosymmetric metals using semiclassical Boltzmann transport formalism by incorporating the effects of Berry curvature and orbital magnetic moment. These effects impart quadratic-B dependence to the magnetoelectric and magnetothermal conductivities, leading to intriguing phenomena such as planar Hall effect, negative magnetoresistance, planar Nernst effect and negative Seebeck effect. The transport coefficients associated with these effects show the usual oscillatory behavior with respect to the angle between the applied electric field and magnetic field. The bands of noncentrosymmetric metals are split by Rashba spin-orbit coupling except at a band touching point. The difference in Fermi surface topology above and below the band touching point is reflected in the nature of magnetoresistance and planar Hall conductivity. For Fermi energy below (above) the band touching point, giant (diminished) negative magnetoresistance is observed. The absolute magnetoresistance and planar Hall conductivity show a decreasing (increasing) trend with Rashba coupling parameter for Fermi energy below (above) the band touching point.

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Thermoelectric and optical probes for a Fermi surface topology change in noncentrosymmetric metals

Cited by 13 publications

References 73 publications

Role of Berry curvature in the generation of spin currents in Rashba systems

Role of Berry curvature in the generation of spin currents in Rashba systems

Dynamical polarization and plasmons in noncentrosymmetric metals

Berry curvature induced magnetotransport in 3D noncentrosymmetric metals

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