共查询到20条相似文献,搜索用时 15 毫秒
1.
Ono S Ando Y Murayama T Balakirev FF Betts JB Boebinger GS 《Physical review letters》2000,85(3):638-641
We measure the normal-state in-plane resistivity of Bi(2)Sr(2-x)La(x)CuO(6+delta) single crystals at low temperatures by suppressing superconductivity with 60 T pulsed magnetic fields. With decreasing hole doping, we observe a crossover from a metallic to an insulating behavior in the low-temperature normal state. This crossover is estimated to occur near 1/8 doping, well inside the underdoped regime, and not at optimum doping as reported for other cuprates. The insulating regime is marked by a logarithmic temperature dependence of the resistivity over two decades of temperature, suggesting that a peculiar charge localization is common to the cuprates. 相似文献
2.
Magnetic-field-induced ordering of electrons around vortices is a striking phenomenon recently found in high-T(c) cuprates. To identify its consequence in the quasiparticle dynamics, the magnetic-field (H) dependence of the low-temperature thermal conductivity kappa of La(2-x)SrxCuO4 crystals is studied for a wide doping range. It is found that the behavior of kappa(H) in the subkelvin region changes drastically across optimum doping, and the data for underdoped samples are indicative of unusual magnetic-field-induced localization of quasiparticles; this localization phenomenon is probably responsible for the unusual "insulating normal state" under high magnetic fields. 相似文献
3.
Jiang-Ping HuShou-Cheng Zhang 《Journal of Physics and Chemistry of Solids》2002,63(12):2277-2282
A key prediction of the SO(5) theory is the antiferromagnetic vortex state. Recent neutron scattering experiment on LSCO superconductors revealed enhanced antiferromagnetic order in the vortex state. Here we review theoretical progress since the original proposal and present a theory of static and dynamic antiferromanetic vortices in LSCO superconductors. It is shown that the antiferromagnetic region induced by the vortices can be greater than the coherence length, due to the light effective mass of the dynamic antiferromagnetic fluctuations at optimal doping, and close proximity to the antiferromagentic state in the underdoped regime. Systematic experiments are proposed to unambiguously determine that the field induced magnetic scattering originates from the vortices and not from the bulk. 相似文献
4.
Chang J Schnyder AP Gilardi R Rønnow HM Pailhes S Christensen NB Niedermayer Ch McMorrow DF Hiess A Stunault A Enderle M Lake B Sobolev O Momono N Oda M Ido M Mudry C Mesot J 《Physical review letters》2007,98(7):077004
High-resolution neutron inelastic scattering experiments in applied magnetic fields have been performed on La1.895Sr0.105CuO4 (LSCO). In zero field, the temperature dependence of the low-energy peak intensity at the incommensurate momentum transfer QIC=(0.5,0.5+/-delta,0),(0.5+/-delta,0.5,0) exhibits an anomaly at the superconducting Tc which broadens and shifts to lower temperature upon the application of a magnetic field along the c axis. A field-induced enhancement of the spectral weight is observed, but only at finite energy transfers and in an intermediate temperature range. These observations establish the opening of a strongly downward renormalized spin gap in the underdoped regime of LSCO. This behavior contrasts with the observed doping dependence of most electronic energy features. 相似文献
5.
Thermodynamic quantities are derived for superconducting and pseudogap regimes by taking into account both amplitude and phase fluctuations of the pairing field. In the normal (pseudogap) state of the underdoped cuprates, two domains have to be distinguished: near the superconducting region, phase correlations are important up to temperature T(phi). Above T(phi), the pseudogap region is determined only by amplitudes, and phases are uncorrelated. Our calculations show excellent quantitative agreement with specific heat and magnetic susceptibility experiments on cuprates. We find that the mean field temperature T0 has a similar doping dependence as the pseudogap temperature T(*), whereas the pseudogap energy scale is given by the average amplitude above T(c). 相似文献
6.
Within the charge-spin separation fermion-spin theory, the influence of a strong external magnetic field on the normal state transport of the underdoped cuprates is discussed. It is shown that when superconductivity in the underdoped cuprates is suppressed in the presence of a strong external magnetic field, the system reveals a low temperature normal state insulator–metal crossover. It is also shown that this striking insulator–metal crossover behavior is intriguingly related to the antiferromagnetic correlation. 相似文献
7.
Sutherland M Li SY Hawthorn DG Hill RW Ronning F Tanatar MA Paglione J Zhang H Taillefer L DeBenedictis J Liang R Bonn DA Hardy WN 《Physical review letters》2005,94(14):147004
Low-temperature heat transport was used to investigate the ground state of high-purity single crystals of the lightly doped cuprate YBa2Cu3O6.33. Samples were measured with doping concentrations on either side of the superconducting phase boundary. We report the observation of delocalized fermionic excitations at zero energy in the nonsuperconducting state, which shows that the ground state of underdoped cuprates is a thermal metal. Its low-energy spectrum appears to be similar to that of the d-wave superconductor, i.e., nodal. The insulating ground state observed in underdoped La2-xSrxCuO4 is attributed to the competing spin-density-wave order. 相似文献
8.
9.
R.S. Markiewicz J. Lorenzana A. Bansil 《Journal of Physics and Chemistry of Solids》2011,72(5):333-336
We have investigated magnetic and charge instabilities of the cuprates within the Gutzwiller approximation RPA (GA+RPA). Interestingly, in GA the dressed Hubbard U is not a single parameter, but has different forms in the spin and charge responses, with distinct doping dependencies. While there are a number of competing magnetic instabilities for hole-doped cuprates, we fail to find any purely electronic charge density waves. The dominant magnetic instabilities are associated with ‘double nesting’, and the phase diagrams are material dependent, with LSCO differing from other cuprates. 相似文献
10.
It was recently demonstrated that in La2-xSrxCuO4 the magnetic-field (H) dependence of the low-temperature thermal conductivity kappa up to 16 T reflects whether the normal state under high magnetic field is a metal or an insulator. We measure the H dependence of kappa in YBa(2)Cu(3)O(y) (YBCO) at subkelvin temperatures for a wide doping range, and find that at low doping the kappa(H) behavior signifies the change in the ground state in this system as well. Surprisingly, the critical doping is found to be located deeply inside the underdoped region, about the hole doping of 0.07 hole/Cu; this critical doping is apparently related to the stripe correlations as revealed by the in-plane resistivity anisotropy. 相似文献
11.
Bobroff J Alloul H Ouazi S Mendels P Mahajan A Blanchard N Collin G Guillen V Marucco JF 《Physical review letters》2002,89(15):157002
We use 89Y NMR in YBa(2)Cu(3)O(6+y) in order to evaluate with high sensitivity the distribution of hole content p in the CuO2 planes. For y=1 and y=0.6, this hole doping distribution is found narrow with a full width at half maximum smaller than Deltap=0.025. This rules out any large static phase separation between underdoped and optimally doped regions in contrast with the one observed by STM in Bi2212 and by NQR in LaSrCuO. This establishes that static electronic phase separation is not a generic feature of the cuprates. 相似文献
12.
The prediction and observation of low-temperature universal thermal conductivity in cuprates has served as a keystone of theoretical approaches to the superconducting state, but recent measurements on underdoped samples show strong violations of this apparently fundamental property of d-wave nodal quasiparticles. Here, we show that the breakdown of universality may be understood as the consequence of disorder-induced magnetic droplets arising from enhanced antiferromagnetic correlations in the underdoped state, even as these same correlations protect the nodal density of states. 相似文献
13.
The thermal conductivity kappa is measured in a series of La2-xSrxCuO4 (0 < or = x < or = 0.22) single crystals down to 90 mK to elucidate the evolution of the residual electronic thermal conductivity kappa(res), which probes the extended quasiparticle states in the d-wave gap. We found that kappa(res)/T grows smoothly, except for a 1/8 anomaly, above x approximately 0.05, and shows no discontinuity at optimum doping, indicating that the behavior of kappa(res)/T is not governed by the metal-insulator crossover in the normal state; as a result, kappa(res)/T is much larger than what the normal-state resistivity would suggest in the underdoped region, which highlights the peculiarities in the low-energy physics in the cuprates. 相似文献
14.
We present measurements of the magnetic penetration depth, lambda(-2)(T), in Pr(2-x)Ce(x)CuO(4-y) and La(2-x)Ce(x)CuO(4-y) films at three Ce doping levels, x, near optimal. Optimal and overdoped films are qualitatively and quantitatively different from underdoped films. For example, lambda(-2)(0) decreases rapidly with underdoping but is roughly constant above optimal doping. Also, lambda(-2)(T) at low T is exponential at optimal and overdoping but is quadratic at underdoping. In light of other studies that suggest both d- and s-wave pairing symmetry in nominal optimally doped samples, our results are evidence for a transition from d- to s-wave pairing near optimal doping. 相似文献
15.
A metal-insulator crossover appears in the experimental data for in-plane resistivity of underdoped cuprates and a range of
superconducting cuprates in the presence of a strong magnetic field suppressing superconductivity. We propose an explanation
for this phenomenon based on a gauge field theory approach to the t-J model. In this approach, based on a formal spin-charge
separation, the low energy effective action describes gapful spinons (with a theoretically derived doping dependence of the
gap m
s
2
∼ δ| ln δ|) and holons with finite Fermi surface (ɛF ∼ tδ) interacting via a gauge field whose basic effect on the spinons is to bind them into overdamped spin waves, shifting their
gap by a damping term linear in T, which causes the metal-insulator crossover. The presence of a magnetic field perpendicular to the plane acts by increasing
the damping, in turn producing a big positive transverse in-plane magnetoresistance at low T, as experimentally observed. 相似文献
16.
We report nuclear magnetic resonance studies on the low-doped n-type copper-oxide Pr(0.91)LaCe(0.09)CuO(4-y) (T(c)=24 K) in the superconducting state and in the normal state uncovered by the application of a strong magnetic field. We find that when the superconductivity is removed the underlying ground state is the Fermi liquid state. This result is at variance with that inferred from previous thermal conductivity measurement and appears to contrast with that in p-type copper oxides with a similar doping level where high-T(c) superconductivity sets in within the pseudogap phase. The data in the superconducting state are consistent with the line-node gap model. 相似文献
17.
Klauss HH Wagener W Hillberg M Kopmann W Walf H Litterst FJ Hucker M Buchner B 《Physical review letters》2000,85(21):4590-4593
The magnetic order of (La,Eu)2-xSrxCuO4 ( x=0.2) has been investigated with &mgr;SR techniques. In this system a low temperature tetragonal (LTT) structure is present in the entire range of doping and it is possible to follow the evolution from the long range antiferromagnetic state at x = 0 to the static magnetic stripes. We find a nonmonotonic change of the Neel temperature with increasing x and the obtained magnetic phase diagram of the LTT phase resembles the generic phase diagram of the cuprates where the superconductivity is replaced by a second antiferromagnetic phase. 相似文献
18.
Colson S Konczykowski M Gaifullin MB Matsuda Y Gierłowski P Li M Kes PH Van Der Beek CJ 《Physical review letters》2003,90(13):137002
Vortex thermal fluctuations in heavily underdoped Bi(2)Sr(2)CaCu(2)O(8+delta) (T(c)=69.4 K) are studied using Josephson plasma resonance. From the zero-field data, we obtain the c-axis penetration depth lambda(L,c)(0)=230+/-10 micrometer and the anisotropy ratio gamma(T). The low plasma frequency allows us to study phase correlations over the whole vortex solid state and to extract a wandering length r(w) of vortex pancakes. The temperature dependence of r(w) as well as its increase with dc magnetic field is explained by the renormalization of the vortex line tension by the fluctuations, suggesting that this softening is responsible for the dissociation of the vortices at the first order transition. 相似文献
19.
We propose to describe the spin fluctuations in the normal state (spin-pseudogap phase) of underdoped high T(c) cuprates as a manifestation of an algebraic spin liquid. Within the slave boson implementation of spin-charge separation, the normal state is described by massless Dirac fermions, charged bosons, and a gauge field. The gauge interaction, as an exact marginal perturbation, drives the mean-field free-spinon fixed point to a new spin-quantum fixed point-the algebraic spin liquid. Luttinger-liquid-like line shapes for the electron spectral function are obtained in the normal state, and we show how a coherent quasiparticle peak appears as spin and charge recombine. 相似文献
20.
Guyard W Sacuto A Cazayous M Gallais Y Le Tacon M Colson D Forget A 《Physical review letters》2008,101(9):097003
Although more than 20 years have passed, the identification of the superconducting order parameter in cuprates is still under debate. Here, we show that the gap size near the nodes is a good candidate for the order parameter: it scales with the critical temperature Tc over a wide doping range and displays a significant temperature dependence below Tc in both the underdoped and the overdoped regimes. In contrast, the gap size at the antinodes does not scale with Tc in the underdoped regime and appears to be controlled by the pseudogap which persists below Tc. 相似文献