arXiv subjects

Seiki Komiya

Publications and source records attributed to Seiki Komiya.

76 records · Page 5Linked to original sources

arXiv2001

Unusual magnetic susceptibility anisotropy in untwinned La_{2-x}Sr_xCuO_4 single crystals in the lightly-doped region

We present a study of the magnetic susceptibility in carefully detwinned La_{2-x}Sr_{x}CuO_4 single crystals in the lightly-doped region (x=0-0.03), which demonstrates a remarkable in-plane anisotropy of the spin system. This anisotropy is found to persist after the long-range antiferromagnetic (AF) order is destroyed by hole doping, suggesting that doped holes break the AF order into domains in which the spin alignment is kept essentially intact. It turns out that the freezing of the spins taking place at low temperatures is also notably anisotropic, implying that the "spin-glass" feature is governed by the domain structure as well.

cond-mat.supr-con↗

arXiv2001

Mobility of the Doped Holes and the Antiferromagnetic Correlations in Underdoped High-T_c Cuprates

The emergence and the evolution of the metallic charge transport in the La_{2-x}Sr_{x}CuO_{4} system from lightly- to optimally-doped samples (x = 0.01 - 0.17) are studied. We demonstrate that in high-quality single crystals the in-plane resistivity shows a metallic behavior for ALL values of x at moderate temperatures and that the hole mobility at 300 K changes only by a factor of 3 from x = 0.01 to 0.17, where its x-dependence is found to be intriguingly similar to that of the inverse antiferromagnetic correlation length. We discuss an incoherent-metal picture and a charged-stripe scenario as candidates to account for these peculiar features.

cond-mat.supr-con↗

arXiv2001

Interplane Transport and Superfluid Density in Layered Superconductors

We report on generic trends in the behavior of the interlayer penetration depth $λ_c$ of several different classes of quasi two-dimensional superconductors including cuprates, Sr$_2$RuO$_4$, transition metal dichalcogenides and organic materials of the $(BEDT-TTF)_2X$-series. Analysis of these trends reveals two distinct patterns in the scaling between the values of $λ_c$ and the magnitude of the DC conductivity: one realized in the systems with a Fermi liquid (FL) ground state and the other seen in systems with a marked deviation from the FL response. The latter pattern is found primarily in under-doped cuprates and indicates a dramatic enhancement (factor $\simeq 10^2$) of the energy scale $Ω_C$ associated with the formation of the condensate compared to the data for the FL materials. We discuss implications of these results for the understanding of pairing in high-$T_c$ cuprates.

cond-mat.supr-con↗

arXiv2000

Carrier concentrations in Bi_{2}Sr_{2-z}La_{z}CuO_{6+δ} single crystals and their relation to Hall coefficient and thermopower

We measured the thermopower S and the Hall coefficients R_H of Bi_{2}Sr_{2-z}La_{z}CuO_{6+δ} (BSLCO) single crystals in a wide doping range, in an effort to identify the actual hole concentrations per Cu, p, in this system. It is found that the "universal" relation between the room-temperature thermopower and T_c does not hold in the BSLCO system. Instead, comparison of the temperature-dependent R_H data with other cuprate systems is used as a tool to identify the actual p value. To justify this approach, we compare normalized R_H(T) data of BSLCO, La_{2-x}Sr_{x}CuO_{4} (LSCO), YBa_{2}Cu_{3}O_{y}, and Tl_{2}Ba_{2}CuO_{6+δ}, and demonstrate that the R_H(T) data of the LSCO system can be used as a template for the estimation of p. The resulting phase diagram of p vs T_c for BSLCO suggests that T_c is anomalously suppressed in the underdoped samples, becoming zero at around p ~ 0.10, while the optimum T_c is achieved at p ~ 0.16 as expected.

cond-mat.supr-con↗