Single-parameter scaling in the magnetoresistance of optimally doped La2−xSrxCuO4

Abstract

We show that the recent magnetoresistance data on thin-film La2−xSrxCuO4 (LSCO) in strong magnetic fields (B) 1 obeys a single-parameter scaling of the form MR(B,, at which point the single-parameter scaling breaks down. The functional form of the MR is distinct from the simple quadratic-tolinear quadrature combination of temperature and magnetic field found in the optimally doped iron superconductor BaFe2(As1−xPx)2 2 . Further, low-temperature departure of the MR in LSCO from its high-temperature scaling law leads us to conclude that the MR curve collapse is not the result of quantum critical scaling. We examine the classical effective medium theory (EMT) previously 3 used to obtain the quadrature resistivity dependence on field and temperature for metals with a T -linear zero-field resistivity. It appears that this scaling form results only for a binary, random distribution of metallic components. More generally, we find a low-temperature, high-field region where the resistivity is simultaneously T and B linear when multiple metallic components are present. Our findings indicate that if mesoscopic disorder is relevant to the magnetoresistance in strange metal materials, the binary-distribution model which seems to be relevant to the iron pnictides is distinct from the more broad-continuous distributions relevant to the cuprates. Using the latter, we examine the applicability of classical effective medium theory to the MR in LSCO and compare calculated MR curves with the experimental data. arXiv:1905.02737v1 [cond-mat.str-el]

Compartmentalizing the cuprate strange metal

“…Indeed, it has already been reported that the MR of LSCO x = 0.19 from Ref. [11] does not obey the quadrature form [59]. Our own analysis of the Giraldo-Gallo data [11] -shown in Figure 5 in the Supplementary Information -reveals that the MR more closely follows H{T 2 scaling.…”

“…the LMR did not appear to obey the H{T quadrature scaling form [59]. (iii) What happens beyond the SC dome?…”

Incoherent transport across the strange metal regime of highly overdoped cuprates

“…x h " βµ 0 H{T , where β " γµ B {αk B and thus ∆ρpT, xq " αk B T a 1 `x2 h. This implies that the timescale associated with the field (1{ω c ) plays a similar role to the thermal time τ h (" h k B T ) in this state (though we stress here that ω c is not necessarily associated with cyclotron motion). Starting from generalities of thermal quantum field theory, it is unclear why this should be the case [32], and even within a more conventional effective medium approach, such 'Planckian quadrature' behavior requires significant fine tuning of parameters [33,34]. Nevertheless, similar behavior has now been reported in both the electrondoped cuprates [12] and in FeSe 1´x S x [14] at or near their putative QCPs, suggesting that it is in fact a generic feature of quantum critical metals.…”

“…[29]) reveals that, just as the T -linear ρ ab pT q persists over a wide doping range beyond p ˚ [2], so too does the anomalous linear MR. In LSCO, the MR at p " p ˚does not follow the quadrature form [34]. The different behaviour in LSCO might be due to the presence of the pseudogap, though clearly more measurements across p ˚are required to establish the role of the pseudogap in causing a breakdown in H{T scaling.…”

$B^2$ to $B$-linear magnetoresistance due to impeded orbital motion

“…Realistic theoretical explanations for this behavior thus far fall into two categories. The first, based on random resistor networks [26,27], attributes QLMR to the presence of disorder, either through real space binary distributions [28], real space patches [29], or doping inhomogeneity [30]. The second is intrinsic and driven by cyclotron orbits in combination with nesting fluctuations or peaks in the density of states arising through hot spots [31], turning points [32], magnetic breakdown [33] or van Hove singularities [34].…”