arXiv subjects

P. L. Kuhns

Publications and source records attributed to P. L. Kuhns.

41 records · Page 3Linked to original sources

arXiv2005

Critical point and the nature of the pseudogap of single-layered copper-oxide Bi$_{2}$Sr$_{2-x}$La$_{x}$CuO$_{6+δ}$ superconductors

We apply strong magnetic fields of H=28.5 \sim 43 T to suppress superconductivity (SC) in the cuprates Bi_{2}Sr_{2-x}La_xCuO_{6+δ} (x=0.65, 0.40, 0.25, 0.15 and 0), and investigate the low temperature (T) normal state by ^{63}Cu nuclear spin-lattice relaxation rate (1/T_1) measurements. We find that the pseudogap (PG) phase persists deep inside the overdoped region but terminates at x \sim 0.05 that corresponds to the hole doping concentration of approximately 0.21. Beyond this critical point, the normal state is a Fermi liquid characterized by the T_1T=const relation. A comparison of the superconducting state with the H-induced normal state in the x=0.40 (T_c = 32 K) sample indicates that there remains substantial part of the Fermi surface even in the fully-developed PG state, which suggests that the PG and SC are coexisting matters.

cond-mat.supr-con↗

arXiv2005

Evidence for Skyrmion crystallization from NMR relaxation experiments

A resistively detected NMR technique was used to probe the two-dimensional electron gas in a GaAs/AlGaAs quantum well. The spin-lattice relaxation rate $(1/T_{1})$ was extracted at near complete filling of the first Landau level by electrons. The nuclear spin of $^{75}$As is found to relax much more efficiently with $T\to 0$ and when a well developed quantum Hall state with $R_{xx}\simeq 0$ occurs. The data show a remarkable correlation between the nuclear spin relaxation and localization. This suggests that the magnetic ground state near complete filling of the first Landau level may contain a lattice of topological spin texture, i.e. a Skyrmion crystal.

cond-mat.mes-hall↗

arXiv2003

Interplay between the magnetic fluctuations and superconductivity in the lanthanum cuprates

We report the analysis of the magnetic fluctuations in the superconducing La_{2-x}Sr_xCuO_4 and the related lanthanum cuprates having the different symmetry of the low temperature structure. The NMR and ESR investigations revealed the dynamical coexistence of the superconductivity and the antiferromagnetic correlations in the large part of superconductivity region of the phase diagram. We show that for all compounds, independent on their low temperature symmetry and on their superconducting properties, the enhancement of the spin stiffness near 1/8 doping takes place.

cond-mat.supr-con↗

arXiv2003

Magnetic phase separation in La1-xSrxCoO3 by 59Co NMR

59Co NMR measurements on La1-xSrxCoO3 reported here establish unequivocally, for the first time, the coexistence of ferromagnetic regions, spin glass regions, and hole poor low spin regions at all x values from 0.1 to 0.5. A zero external field NMR spectrum, which is assigned to the ferromagnetic regions, has a spectral shape which is nearly x independent at 1.9 K, as are the relaxation times, T1 and T2. The integrated spectral area increases rapidly with x up to x=0.2 and then becomes almost constant for larger x. In a field of 9.97 T, a narrow NMR line is observed at 102 MHz, identical to that found in x=0 samples in previous work. The integrated intensity of this spectrum decreases rapidly with increasing x, and is ascribed to hole poor low spin regions. Beneath this spectrum, a third broad line, centered at 100 MHz, with shorter T1 and T2,. is assigned to a spin glass, intermediate spin phase.

cond-mat.str-el↗

arXiv1998

Magnetic field independence of the spin gap in YBa_2Cu_3O_{7-delta}

We report, for magnetic fields of 0, 8.8, and 14.8 Tesla, measurements of the temperature dependent ^{63}Cu NMR spin lattice relaxation rate for near optimally doped YBa_2Cu_3O_{7-delta}, near and above T_c. In sharp contrast with previous work we find no magnetic field dependence. We discuss experimental issues arising in measurements of this required precision, and implications of the experiment regarding issues including the spin or pseudo gap.

cond-mat.str-el↗