Correlation between scale-invariant normal-state resistivity and superconductivity in an electron-doped cuprate

Abstract

An understanding of the normal state in the high-temperature superconducting cuprates is crucial to the ultimate understanding of the long-standing problem of the origin of the superconductivity itself. This so-called “strange metal” state is thought to be associated with a quantum critical point (QCP) hidden beneath the superconductivity. In electron-doped cuprates—in contrast to hole-doped cuprates—it is possible to access the normal state at very low temperatures and low magnetic fields to study this putative QCP and to probe the T ➔ 0 K state of these materials. We report measurements of the low-temperature normal-state magnetoresistance (MR) of the n-type cuprate system La2−xCexCuO4 and find that it is characterized by a linear-in-field behavior, which follows a scaling relation with applied field and temperature, for doping (x) above the putative QCP (x = 0.14). The magnitude of the unconventional linear MR decreases as Tc decreases and goes to zero at the end of the superconducting dome (x ~ 0.175) above which a conventional quadratic MR is found. These results show that there is a strong correlation between the quantum critical excitations of the strange metal state and the high-Tc superconductivity.

Possible superconductivity from incoherent carriers in overdoped cuprates

“…The form of the (magneto)resistivity found in OD cuprates is similar to that observed in other correlated metals close to a QCP [24][25][26]. Uniquely, in OD cuprates, this T -and H-linear resistivity exists across the entire strange metal regime [16], suggesting that it is not tied to any singular QCP [27].…”

Possible scale invariant linear magnetoresistance in pyrochlore iridates Bi2Ir2O7

“…Recently, there are several reports of the observation of scale invariant linear magnetoresistance close to the quantum critical points in high temperature superconducting cuprates and iron pnictides [29][30][31][32]. From a phenomenological point of view, the MR of Bi 2 Ir 2 O 7 shows striking similarity to these two systems: the resistivity depends linearly on field as temperature approaches zero, and the zero-field temperature dependence of resistivity also becomes linear at high temperatures.…”

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

“…Moreover, stateof-the-art optical conductivity measurements have indicated that the scattering rate in LSCO increases with increasing B [67], a possible direct manifestation of impeded cyclotron motion. The QLMR observed in electron doped cuprates [14], on the other hand, is unlikely to originate from proximity to a vHs. Instead, hot spots associated with the proximate AFM order is the most likely source of impeded orbital motion [68,69].…”

“…In those materials that have been shown to exhibit quadrature scaling, no violation of linearity has been observed to the highest B/T values attained thus far: up to B/T = 35 T/K in electron-doped cuprates with an estimated turnover scale of 2-3 T/K [14] and up to 25 T/K in hole-doped cuprates with a turnover scale of 0.2 T/K [16]. This unwavering Blinearity up to the highest B/T is one of the hallmarks of quadrature scaling.…”

“…Since its discovery in the pnictides, QLMR has been observed in iron chalcogenides near a nematic QCP [10,11], in heavy fermions near a Kondo QCP [9,12], in CrAs near a double helical endpoint [13] and in the electron- [14] and hole-doped cuprates both inside [15] and outside [16] of the pseudogap regime. In almost all cases, ρ(T ) also exhibits a dominant T -linear dependence at low T and zero field that has been linked to Planckian dissipation -the maximum dissipation allowed by quantum mechanics [10,[17][18][19][20][21].…”