Reduced Hall carrier density in the overdoped strange metal regime of cuprate superconductors

Abstract

Efforts to understand the microscopic origin of superconductivity in the cuprates are dependent on knowledge of the normal state. The Hall number in the low-temperature, high-field limit n H (0) has a particular importance because, within conventional transport theory, it is simply related to the number of charge carriers, so its evolution with doping gives crucial information about the nature of the charge transport. Here we report a study of the high-field Hall coefficient of the single-layer cuprates Tl 2 Ba 2 CuO 6+δ (Tl2201) and (Pb/La)-doped Bi 2 Sr 2 CuO 6+δ (Bi2201), which shows how n H (0) evolves in the overdoped-so-called strange metal-regime of cuprates. We find that n H (0) increases smoothly from p to 1 + p, where p is the number of holes doped into the parent insulating state, over a wide range of doping. The evolution of n H correlates with the emergence of the anomalous linear-in-temperature term in the low-temperature in-plane resistivity. The results could suggest that quasiparticle decoherence extends to dopings well beyond the pseudogap regime.

Normal state specific heat in the cuprate superconductors La2−xSrxCuO4 and Bi2

“…4, interpreted as a sharp nearly twofold drop in carrier density with decreasing p [11]. A similar decrease has been reported by Putzke et al [10] and a very similar drop was observed previously in YBCO [8] and Nd-LSCO [9]. This drop has been identified as a key signature of the pseudogap phase that reveals a transformation of the Fermi surface across p ⋆ , consistent with a change from a large surface containing 1 + p holes to small Fermi pockets containing p holes [32,43].…”

“…[1,2]inTl 2 Ba 2 CuO 6+δ ), the measured carrier concentration is equal to n H = 1 + p (per CuO 2 plane), and the Sommerfeld coefficient is on the order of 5 mJ mol −1 K −2 [3][4][5][6]. On the other hand, for p p ⋆ , angle-resolved photoemission spectroscopy (ARPES) stud-ies show that the Fermi surface breaks into small nodal "Fermi arcs" [7] and Hall effect measurements then indicate that the carrier concentration drops to n H = p in YBa 2 Cu 3 O y (YBCO) [8], Nd 0.4 La 1.6−x Sr x CuO 4 (Nd-LSCO) [9], and Bi 2+y Sr 2−x−y La x CuO 6+δ (Bi2201) [10,11].…”

Possible superconductivity from incoherent carriers in overdoped cuprates

“…In reality, the normal state transport properties of all OD cuprates, including Tl2201, are far from conventional. This so-called 'strange metal' regime has three notable characteristics: (i) a ubiquitous non-FL (T -linear) component in the in-plane resistivity ρ ab (T ) at low T [10][11][12], whose coefficient α(0) scales with T c and is consistent with a scattering rate at the Planckian dissipation limit ħ h/τ ∼ k B T [12,13]; (ii) a Hall number n H (0) deduced from the low-T Hall effect that does not follow the expected 'Luttinger' 1 + p line but instead drops monotonically towards p near OP doping [14] and (iii) a H-linear magnetoresistance (MR) at high field strengths [15] that exhibits H/T scaling [16] and is also insensitive to both field orientation and impurity scattering rate [16] (for more details, see the introduction to appendix A).…”

“…where the Fermi level ε F crosses a van Hove singularity (vHs) -may result in a Tlinear resistivity down to 0 K [18]. While the two cuprate families considered here are known to host a vHs crossing somewhere in their phase diagram, across the doping region of interest (0.20 < p < 0.30), ε F in LSCO is tuned away from the vHS, while in Tl2201, ε F is tuned towards it [14]. The evolution of the T -linear coefficient with doping in both systems, however, is very similar [12,13].…”

“…Moreover, the observed H/T scaling of the MR [16] implies a direct link between the non-orbital MR and Planckian dissipation. The drop in the low-T Hall carrier density n H (0) with decreasing doping [14] -a drop that is larger than any residual field dependence in R H at low T [14,23] -can also be viewed as a signature of carriers with no intrinsic Lorentzdriven Hall response. Overall, these various transport anomalies reveal a consistent picture in which quasiparticle coherence is gradually suppressed as optimal doping is approached from the overdoped side.…”