arXiv subjects

Takeshi Kondo

Publications and source records attributed to Takeshi Kondo.

93 records · Page 6Linked to original sources

arXiv2008

Charge density wave origin of cuprate checkerboard visualized by scanning tunneling microscopy

One of the main challenges in understanding high TC superconductivity is to disentangle the rich variety of states of matter that may coexist, cooperate, or compete with d-wave superconductivity. At center stage is the pseudogap phase, which occupies a large portion of the cuprate phase diagram surrounding the superconducting dome [1]. Using scanning tunneling microscopy, we find that a static, non-dispersive, "checkerboard"-like electronic modulation exists in a broad regime of the cuprate phase diagram and exhibits strong doping dependence. The continuous increase of checkerboard periodicity with hole density strongly suggests that the checkerboard originates from charge density wave formation in the anti-nodal region of the cuprate Fermi surface. These results reveal a coherent picture for static electronic orderings in the cuprates and shed important new light on the nature of the pseudogap phase.

cond-mat.str-el↗

arXiv2007

Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+x

The nature of the pseudogap state, observed above the superconducting transition temperature TC in many high temperature superconductors, is the center of much debate. Recently, this discussion has focused on the number of energy gaps in these materials. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here we report on temperature dependent scanning tunneling spectroscopy of Pb-Bi2Sr2CuO6+x. We have found a new, narrow, homogeneous gap that vanishes near TC, superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results not only support the two gap picture, but also explain previously troubling differences between scanning tunneling microscopy and other experimental measurements.

cond-mat.supr-con↗

arXiv2006

Evidence for two energy scales in the superconducting state of optimally doped (Bi,Pb)2(Sr,La)2CuO6+d

We use angle-resolved photoemission spectroscopy (ARPES) to investigate the properties of the energy gap(s) in optimally doped (Bi,Pb)2(Sr,La)2CuO6+d (Bi2201). We find that the spectral gap has two components in the superconducting state: a superconducting gap and pseudogap. Significant differences in their momentum and temperature dependence suggest that they represent two separate energy scales. Spectra near the node reveal a sharp peak with a small gap below Tc that closes at Tc. Near the antinode, the spectra are broad with a large energy gap of ~40meV above and below Tc. The spectral shape and gap magnitude around the antinode are almost constant across Tc, which indicates that the pseudogap state coexists with the superconducting state below Tc, and it dominates the character of the spectra around the antinode. We speculate that the pseudogap state competes with the superconductivity by diminishing spectral weight in the antinodal regions, where the magnitude of the superconducting gap is largest.

cond-mat.supr-con↗