Charge transfer to the local singlet states as a function of Li content in La2Cu1−Li O4 and La1.85Sr0.15Cu1−Li O4

Rykov, Alexandre I.; Yaśuoka, Hiroshi; Ueda, Yutaka

doi:10.1016/0921-4534(95)00135-2

Cited by 41 publications

(25 citation statements)

References 37 publications

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“…This crossover, however, has not been explicitly investigated experimentally. Here, we report a cold neutron inelastic scattering study on spin dynamics in Li doped La 2 CuO 4 from 150 K to 1.5 K. A crossover from the ω/T scaling to a new low temperature regime, which features an infrared energy cutoff, is directly observed.The critical doping concentration, y c , for Li doped La 2 CuO 4 is 3% [7,8]. In this study, a y=6% single crystal, La 2 Cu 0.94 Li 0.06 O 4 , weighing 2.1 g, was grown in CuO flux, using isotopically enriched 7 Li (98.4%) to reduce neutron absorption of natural Li.…”

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Novel Dynamic Scaling Regime in Hole-DopedLa2CuO4

Bao¹,

Chen²,

Qiu³

et al. 2003

Phys. Rev. Lett.

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Only 3% hole doping by Li is sufficient to suppress the long-range 3-dimensional (3D) antiferromagnetic order in La2CuO4. The spin dynamics of such a 2D spin liquid state at T ≪ J was investigated with measurements of the dynamic magnetic structure factor S(ω, q), using cold neutron spectroscopy, for single crystalline La2Cu0.94Li0.06O4. S(ω, q) peaks sharply at (π, π) and crosses over around 50 K from ω/T scaling to a novel low temperature regime characterized by a constant energy scale. The possible connection to a crossover from the quantum critical to the quantum disordered regime of the 2D antiferromagnetic spin liquid is discussed.The experimental investigation of the spin dynamics of doped Heisenberg antiferromagnets on a square lattice is essential to understanding cuprate superconductors, as well as to current research on quantum phase transitions [1]. For the structurally simplest laminar cuprate, La 2 CuO 4 , the 3-dimensional (3D) antiferromagnetic Néel order due to weak interlayer magnetic interaction can be suppressed by 2-3% hole doping using Sr, Ba or Li, thus allowing experimental investigation of the quantum spin dynamics of a 2-dimensional (2D) spin liquid in a wide temperature range, 0At the critical doping concentration, y c , of La 2 CuO 4 and at T = 0, namely at the quantum critical point, spin dynamics is described by classical critical dynamics in 2+1 dimensions [2]. At a finite temperature, the extra dimension in imaginary time is reduced to a finite thickness ofhc/k B T , where c is the spin wave velocity. As a consequence of this long wavelength cutoff, spin dynamics follows the quantum criticalhω/k B T scaling [3]. This has been experimentally observed in Ba and Sr doped La 2 CuO 4 in previous inelastic neutron scattering studies [4,5,6]. At T = 0 and above the critical doping concentration y > y c , zero-point quantum fluctuations set another long wavelength cutoff. Therefore, for y > y c , when the thermal cutoff length,hc/k B T , reaches the quantum cutoff during cooling, a crossover in spin dynamics from the quantum critical (QC) regime, where the energy scale is k B T , to the quantum disordered (QD) regime, where the energy scale is fixed at infrared by the quantum cutoff, occurs [2,3]. This crossover, however, has not been explicitly investigated experimentally. Here, we report a cold neutron inelastic scattering study on spin dynamics in Li doped La 2 CuO 4 from 150 K to 1.5 K. A crossover from the ω/T scaling to a new low temperature regime, which features an infrared energy cutoff, is directly observed.The critical doping concentration, y c , for Li doped La 2 CuO 4 is 3% [7,8]. In this study, a y=6% single crystal, La 2 Cu 0.94 Li 0.06 O 4 , weighing 2.1 g, was grown in CuO flux, using isotopically enriched 7 Li (98.4%) to reduce neutron absorption of natural Li. The crystal has orthorhombic Cmca symmetry with lattice parameters a = 5.351Å, b = 13.15Å and c = 5.386Å at 295 K. Using this orthorhombic unit cell to label reciprocal q space, the (π, π) point in the square latt...

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“…The critical doping concentration, y c , for Li doped La 2 CuO 4 is 3% [7,8]. In this study, a y=6% single crystal, La 2 Cu 0.94 Li 0.06 O 4 , weighing 2.1 g, was grown in CuO flux, using isotopically enriched 7 Li (98.4%) to reduce neutron absorption of natural Li.…”

mentioning

confidence: 99%

Novel Dynamic Scaling Regime in Hole-DopedLa2CuO4

Bao¹,

Chen²,

Qiu³

et al. 2003

Phys. Rev. Lett.

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“…For estimating J c , field-dependent isothermal magnetization hysteresis curves were obtained at 5 K. For LSCO, alattice parameter along with total volume decrease, while the c/a increases when Li presumably substitutes Cu. 22 After annealing Tl-2223 in Ar+4%H 2 , a = 3.84972(8) Å while a slight increase in c (35.656(1) Å) was observed. Similar increase in the caxes were observed in all other Li added samples.…”

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confidence: 99%

Effect of Li2O on the microstructure, magnetic and transport properties of Tl-2223 superconductor

Shipra

Sefat

2015

Physica C: Superconductivity and its Applications

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The present study gives an account of the effect of Li 2 O on the ease of phase formation and superconducting properties of Tl 2 Ba 2 Ca 2 Cu 3 O 10+δ (Tl-2223) material. Li substitution only slightly decreases the superconducting transition temperature, while the optimal concentration of 20% doping improves the critical current density (J c ) by ~ two fold. We found substantial effects on the synthesis temperature, microstructure and normal state transport properties of Tl-2223 with Li 2 O addition. Short-time thermal annealing under flowing Ar+4%H 2 (1 hr.) further improves the superconducting volume fractions, as well as J c .

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“…Compounds containing formally trivalent copper are rare, La 2 Cu 0.5 Li 0.5 O 4 providing one of the few examples [2]. In the cuprates doped holes are believed to occupy oxygen 2p s orbitals which hybridize with the Cu d x 2 2y 2 orbital to form a d 9L (L ligand hole) configuration.…”

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Magnetic Excitations of the Doped-Hole State in DiamagneticLa2Cu0.5Li0.5<

et al. 1996

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Substitution of Li for Cu in La 2 Cu 12x Li x O 4 donates holes; at x 0.5 the Li ions form an ordered superlattice which isolates individual CuO 4 plaquettes from one another, and the number of doped holes is sufficient that each plaquette is occupied. Above 170 K, an activated temperature dependence of the Cu nuclear spin relaxation rate reveals a magnetic excitation of the doped-hole state with an energy of ϳ130 meV. Below 170 K relaxation is primarily due to fluctuations of the electric field gradient; the temperature dependence of this rate is anomalously slow: T 21 1~p T .[S0031-9007(96)01098-8]

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Charge transfer to the local singlet states as a function of Li content in La2Cu1−Li O4 and La1.85Sr0.15Cu1−Li O4

Cited by 41 publications

References 37 publications

Novel Dynamic Scaling Regime in Hole-DopedLa2CuO4

Novel Dynamic Scaling Regime in Hole-DopedLa2CuO4

Effect of Li2O on the microstructure, magnetic and transport properties of Tl-2223 superconductor

Magnetic Excitations of the Doped-Hole State in DiamagneticLa2Cu0.5Li0.5<

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