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 B… Show more
“…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].…”
Section: B Bi 2+y Sr 2−x−y La X Cuo 6+δsupporting
confidence: 79%
“…[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].…”
The specific heat C of the cuprate superconductors La2−xSrxCuO4 and Bi2+ySr2−x−yLaxCuO6+ was measured at low temperatures (down to 0.5 K) for dopings p close to p, the critical doping for the onset of the pseudogap phase. A magnetic field up to 35 T was applied to suppress superconductivity, giving direct access to the normal state at low temperatures, and enabling a determination of Ce, the electronic contribution to the normal-state specific heat at T→0. In La2−xSrxCuO4 at x=p=0.22, 0.24 and 0.25, Ce/T=15to16mJmol−1K−2 at T=2K, values that are twice as large as those measured at higher doping (p>0.3) and lower doping (p<0.15). This confirms the presence of a broad peak in the doping dependence of Ce at p0.19 as previously reported for samples in which superconductivity was destroyed by Zn impurities. Moreover, at those three dopings, we find a logarithmic growth as T→0 such that Ce/TBln(T0/T). The peak versus p and the logarithmic dependence versus T are the two typical thermodynamic signatures of quantum criticality. In the very different cuprate Bi2+ySr2−x−yLaxCuO6+, we again find that Ce/TBln(T0/T) at pp, strong evidence that this ln(1/T) dependence of the electronic specific heat-first discovered in the cuprates La1.8−xEu0.2SrxCuO4 and La1.6−xNd0.4SrxCuO4-is a universal property of the pseudogap critical point.
“…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].…”
Section: B Bi 2+y Sr 2−x−y La X Cuo 6+δsupporting
confidence: 79%
“…[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].…”
The specific heat C of the cuprate superconductors La2−xSrxCuO4 and Bi2+ySr2−x−yLaxCuO6+ was measured at low temperatures (down to 0.5 K) for dopings p close to p, the critical doping for the onset of the pseudogap phase. A magnetic field up to 35 T was applied to suppress superconductivity, giving direct access to the normal state at low temperatures, and enabling a determination of Ce, the electronic contribution to the normal-state specific heat at T→0. In La2−xSrxCuO4 at x=p=0.22, 0.24 and 0.25, Ce/T=15to16mJmol−1K−2 at T=2K, values that are twice as large as those measured at higher doping (p>0.3) and lower doping (p<0.15). This confirms the presence of a broad peak in the doping dependence of Ce at p0.19 as previously reported for samples in which superconductivity was destroyed by Zn impurities. Moreover, at those three dopings, we find a logarithmic growth as T→0 such that Ce/TBln(T0/T). The peak versus p and the logarithmic dependence versus T are the two typical thermodynamic signatures of quantum criticality. In the very different cuprate Bi2+ySr2−x−yLaxCuO6+, we again find that Ce/TBln(T0/T) at pp, strong evidence that this ln(1/T) dependence of the electronic specific heat-first discovered in the cuprates La1.8−xEu0.2SrxCuO4 and La1.6−xNd0.4SrxCuO4-is a universal property of the pseudogap critical point.
“…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).…”
Section: Introductionmentioning
confidence: 62%
“…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].…”
Section: Introductionmentioning
confidence: 94%
“…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.…”
There is now compelling evidence that the normal state of
superconducting overdoped cuprates is 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)ns(0)
of overdoped cuprates exhibits an anomalous depletion with increased
hole doping pp,
falling to zero at the edge of the superconducting dome. Over the same
doping range, the effective zero-temperature Hall number
n_{\rm H}(0)
transitions from pp
to 1 + pp.
By taking into account the presence of these two charge sectors, we
demonstrate that in the overdoped cuprates
Tl_22Ba_22CuO_{6+\delta}6+δ
and La_{2-x}2−xSr_xxCuO_44,
the growth in n_s(0)ns(0)
as pp
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.
A review of the phenomenology and microscopy of cuprate superconductors is presented, with particular attention to universal conductance features, which reveal the existence of two electronic subsystems. The overall electronic system consists of $$1+p$$
1
+
p
charges, where p is the doping. At low dopings, exactly one hole is localized per planar copper–oxygen unit, while upon increasing doping and temperature, the hole is gradually delocalized and becomes itinerant. Remarkably, the itinerant holes exhibit identical Fermi liquid character across the cuprate phase diagram. This universality enables a simple count of carrier density and yields comprehensive understanding of the key features in the normal and superconducting state. A possible superconducting mechanism is presented, compatible with the key experimental facts. The base of this mechanism is the interaction of fast Fermi liquid carriers with localized holes. A change in the microscopic nature of chemical bonding in the copper oxide planes, from ionic to covalent, is invoked to explain the phase diagram of these fascinating compounds.
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