Search

Abstract The signature feature of the ‘strange metal’ state of high-T c cuprates—its linear-in-temperature resistivity—has a coefficient α 1 that correlates with T c , as expected were α 1 derived from scattering off the same bosonic fluctuations that mediate pairing. Recently, an anomalous linear-in-field magnetoresistance (=γ 1 H) has also been observed, but only over a narrow doping range, leaving its relation to the strange metal state and to the superconductivity unclear. Here, we report in-plane magnetoresistance measurements on three hole-doped cuprate families spanning a wide range of temperatures, magnetic field strengths and doping. In contrast to expectations from Boltzmann transport theory, γ 1 is found to correlate universally with α 1. A phenomenological model incorporating real-space inhomogeneity is proposed to explain this correlation. Within this picture, superconductivity in hole-doped cuprates is governed not by the strength of quasiparticle interactions with a bosonic bath, but by the concentration of strange metallic carriers.

Strange metals exhibit a variety of anomalous magnetotransport properties, the most striking of which is a resistivity that increases linearly with magnetic field B over a broad temperature and field range. The ubiquity of this behavior across a spectrum of correlated metals—both single- and multiband, with either dominant spin and/or charge fluctuations, of varying levels of disorder or inhomogeneity, and in proximity to a quantum critical point or phase—obligates the search for a fundamental underlying principle that is independent of the specifics of any material. Strongly anisotropic (momentum-dependent) scattering can generate B-linear magnetoresistance but only at intermediate field strengths. At high enough fields, the magnetoresistance must eventually saturate. Here, we consider the ultimate limit of such anisotropy, a region or regions on the Fermi surface that impede all orbital (cyclotron) motion through them, but whose imposition can be modelled nonetheless through a modified Boltzmann theoretical treatment. Application of the proposed theorem suggests that the realization of quadratic-to-linear magnetoresistance requires the presence of a bounded sector on the Fermi surface possibly separating two distinct types of carriers. While this bounded sector may have different origins or manifestations, we expect its existence to account for the anomalous magnetotransport found in a wide range of correlated materials.

Strange metals possess transport properties that are markedly different from those of a conventional Fermi liquid. Despite strong similarities in behavior exhibited by distinct families, a consistent description of strange metallic transport and, in particular, its evolution from low to high magnetic field strength H, is still lacking. The electron nematic FeSe_{1−x}S_{x} is one such strange metal displaying anomalous H/T scaling in its transverse magnetoresistance as well as a separation of transport and Hall lifetimes at low H beyond its (nematic) quantum critical point at x_{c}∼0.17. Here we report a study of the Hall response of FeSe_{1−x}S_{x} across x_{c} in fields up to 33 T. Upon subtraction of a normal H-linear component from the total Hall response (imposed by perfect charge compensation), we find a second component, ascribable to strange metal physics, that grows as 1/T upon approach to the quantum critical point. Through this decomposition, we reveal that lifetime separation is indeed driven primarily by the presence of the strange metal component.

The non-superconducting state of overdoped cuprates is conjectured to be a strange metal comprising two distinct charge sectors, one governed by coherent quasiparticle excitations, the other seemingly incoherent and characterized by non-quasiparticle (Planckian) dissipation. The zero-temperature superfluid density n_s(0) of overdoped cuprates exhibits an anomalous depletion with increased hole doping p, falling to zero at the edge of the superconducting dome. Over the same doping range, the effective zero-temperature Hall number n_H(0) transitions from p to 1 + p. By taking into account the presence of these two charge sectors, we demonstrate that in the overdoped cuprates Tl2Ba2CuO6+\delta and La2-xSrxCuO4, the growth in n_s(0) as p is decreased from the overdoped side may be compensated by the loss of carriers in the coherent sector. Such a correspondence is contrary to expectations from conventional BCS theory and implies that superconductivity in overdoped cuprates emerges uniquely from the sector that exhibits incoherent transport in the normal state.