Interlayer coherency and angular-dependent magnetoresistance oscillations in quasi-two-dimensional conductors

2013

Phys. Rev. B

The longitudinal interlayer magnetoresistance Rzz (Bz) is calculated in strongly anisotropic layered metals, when the interlayer band width 4tz is less than the Landau level separation ωc. The impurity scattering has much stronger effect in this regime than in 3D metals and leads to a linear longitudinal interlayer magnetoresistance Rzz ∝ Bz in the interval ωc > 4tz >> √ Γ0 ωc changing to a square-root dependence Rzz ∝ B 1/2 z at higher field or smaller tz. The crossover field allows to estimate the interlayer transfer integral as tz ∼ √ Γ0 ωc. Longitudinal interlayer magnetoresistance, being robust to the increase of temperature or long-range disorder, is easy for measurements and provides a useful tool to investigate the electronic structure of quasi-two-dimensional compounds.PACS numbers: 72.15. Gd,73.43.Qt,74.70.Kn, The investigation of angular and field dependence of magnetoresistance (MR) provides a powerful tool of studying the electronic properties of various metals, including strongly anisotropic layered compounds, such as organic metals (see, e.g., Refs. [1-4] for reviews), cuprate and ironbased high-temperature superconductors,(see, e.g., [5][6][7][8][9][10][11][12][13][14]) heterostructures [15] etc. In layered quasi-two-dimensional (Q2D) metals with at least monoclinic crystal symmetry the electron dispersion in the tight-binding approximation is given bywhere the 2D electron dispersion in magnetic field perpendicular to conducting layers is quantized in Landau levels:where the Landau level (LL) separation ω c = eB/m * c, m * is the effective electron mass, n is the LL number, γ ≈ 1/2, k z is out-of-plane electron momentum, and d is the interlayer spacing. If the interlayer transfer integral t z ≫ ω c , the standard 3D theory of galvanomagnetic properties [17][18][19] can be applied, which is valid in the lowest order of the parameter ω c /t z . This theory predicts some special features of MR in Q2D metals: the angular magnetoresistance oscillations (AMRO) [20][21][22] and the beats of the amplitude of magnetic quantum oscillations (MQO). [18] In more anisotropic Q2D metals, when t z ω c , several new features appear, such as slow MR oscillations [23,24] and the phase shift of MQO beats between transport and thermodynamic quantities. [24,25] These two effects are not described by the standard 3D theory [17][18][19] because they appear in the higher orders in the parameter ω c /t z . The monotonic part of MR also changes when ω c /t z ∼ 1. According to the standard theory, [17] external magnetic field along the electric current leads only to MQO but does not influence the monotonic (background) part of this current.[26] However, the monotonic growth of interlayer MR R zz with the increase of longitudinal magnetic field B z was observed in various compounds as a general feature of Q2D metals.[23, 27-34] Its theoretical description is the aim of the present paper.In very anisoropic and dirty compounds with t z ≪ Γ 0 , ω c , where Γ 0 = /2τ 0 and τ 0 is electron mean free time in the absence of magneti...

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confidence: 75%

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confidence: 99%

Longitudinal interlayer magnetoresistance in strongly anisotropic quasi-two-dimensional metals

2013

Phys. Rev. B

“…Then Z(n, p) ≈ J 2 p (k F d tan θ) can be factored out from the sum over n in Eq. (13). Substituting Eq.…”

Section: 22mentioning

confidence: 99%

Angular dependence of magnetoresistance in strongly anisotropic quasi-two-dimensional metals: Influence of Landau-level shape

Mogilyuk

2014

Phys. Rev. B

We present the quantum-mechanical calculations of the angular dependence of interlayer conductivity σzz(θ) in a tilted magnetic field in quasi-2D layered metals. Our calculation shows that the LL shape is important for this angular dependence. In particular, the amplitude of angular magnetoresistance oscillations (AMRO) is much stronger for the Gaussian LL shape than for the Lorentzian. The ratio σzz (θ = 0) /σzz (θ → ±90• ) is also several times larger for the Gaussian LL shape. AMRO and Zeeman energy splitting lead to a spin current. For typical organic metals and for a medium magnetic field 10T this spin current is only a few percent of the charge current, but its value may almost reach the charge current for special tilt angles of magnetic field. The spin current has strong angular oscillations, which are phase-shifted as compared to the usual AMRO.

“…[12][13][14] for recent reviews), heterostructures [15] etc. The standard threedimensional theory of MR [13,[16][17][18], based on the τ -approximation, is not valid in the two-dimensional (2D) electron system because of the high Landau-level (LL) degeneracy (see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

Crossover from the weak to strong-field behavior of the longitudinal interlayer magnetoresistance in quasi-two-dimensional conductors

Low Temperature Physics

2014

We investigate the monotonic growth of longitudinal interlayer magnetoresistanceRzz (Bz), analytically and numerically in the self-consistent Born approximation. We show that in a weak magnetic field the monotonic part ofRzz (Bz) is almost constant and starts to grow only above the crossover field Bc, when the Landau levels (LL) become isolated, i.e. when the LL separation becomes greater than the LL broadening. In higher field Bz ≫ Bc,Rzz (Bz) ∝ B 1/2 z in agreement with previous works.