Magnetic scaling in the underdoped superconductorHg0.8Re0.2Ba2

Abstract

An approach has been made to deduce the second moment contribution of the planar Cu NMR line from indirect nuclear couplings, using the middle plane sites of the trilayer superconductor, Hg 0.8 Re 0.2 Ba 2 Ca 2 Cu 3 O 8 (T c ϭ126 K). We find that T 1 fluctuations of neighboring nuclear spins in the plane are the dominant causes of the spin-echo decay observed in the present case of an external field perpendicular to the c axis. Taking account of this effect in the analysis, the second moment is deduced. From the T dependences of the T 1 and second moment thus obtained, we find the dynamical exponent, zϭ2. The present result indicates that the boundary of z crossing from 2 ͑overdamped regime͒ to 1 ͑quantum critical regime͒ may be shifted more closely to the antiferromagnetic phase than previously assumed. It is also shown that the pseudogap is not a specific feature to the zϭ1 region. ͓S0163-1829͑99͒50922-3͔ RAPID COMMUNICATIONS R14 170PRB 59 GOTO, SHIMIZU, SASTRY, AND SCHWARTZ 24 This is the expression for the systems with axial symmetry, and in the static limit. RAPID COMMUNICATIONS R14 172PRB 59 GOTO, SHIMIZU, SASTRY, AND SCHWARTZ

Origin of the Enhanced Copper Spin Echo Decay Rate in the Pseudogap Regime of the Multilayer High-TcCuprates

“…Each curve was obtained by adding the real part of the FT spectra of the half echo measured at a few different frequencies [12]. The relatively narrow and wide lines are assigned to Cu(1) and Cu(2) sites in the inner and outer layers, respectively [13]. We confirmed that K s and the quadrupole frequency (ν Q ) are consistent with previous results [14,15].…”

“…(11). Provided again that the q-dependences of χ ij (q) around Q are weaker than that of F q , T −2 2M at 0 • and 90 • can be rewritten as [6,13],…”

Magnetoresistance in High-TcSuperconductors: The Role of Vertex Corrections

“…According to the SCR theory [23] or the renormalization group study [24], ξ 2 AF ∝ (T + c) −1 in two-dimensional systems, which is observed in high-T c cuprates around the optimum doping [25]. This relation is also reproduced well by the FLEX approximation [15].…”

Uniform hole doping in HgBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{8+δ}$ studied by $^{63}$Cu NMR

“…The hole concentration p is estimated from[8]. A triangle[4], a cross[6], a square[5], and closed circles (the present works) indicate pseudogap temperatures T * 's. Open circles are T c 's.…”

“…The spin pseudogap opens below T * . The Cu nuclear spin-lattice relaxation studies revealed the pseudogap for underdoped single crystals with T c = 115 K (T * = 230 K) [4], an underdoped Re-substituted powder sample with T c = 126 K (T * = 172 K) [5], and an optimally doped powder sample with T c = 133 K (T * = 160 K) [6,7]. Closed circles and crosses are for as-synthesized and O 2 -annealed samples, respectively.…”