Shunsuke Yoshizawa

Robust protection from backscattering in the topological insulator Bi1.5Sb0.5Te1.7Se1.3.

Electron scattering in the topological surface state (TSS) of the topological insulator Bi1.5Sb0.5Te1.7Se1.3 was studied using quasiparticle interference observed by scanning tunneling microscopy. It was found that not only the 180° backscattering but also a wide range of backscattering angles of 100°-180° are effectively prohibited in the TSS. This conclusion was obtained by comparing the observed scattering vectors with the diameters of the constant-energy contours of the TSS, which were measured for both occupied and unoccupied states using time- and angle-resolved photoemission spectroscopy. The robust protection from backscattering in the TSS is good news for applications, but it poses a challenge to the theoretical understanding of the transport in the TSS.

Imaging Josephson vortices on the surface superconductor Si(111)-(√7×√3)-In using a scanning tunneling microscope.

We have studied the superconducting Si(111)-(√7×√3)-In surface using a ³He-based low-temperature scanning tunneling microscope. Zero-bias conductance images taken over a large surface area reveal that vortices are trapped at atomic steps after magnetic fields are applied. The crossover behavior from Pearl to Josephson vortices is clearly identified from their elongated shapes along the steps and significant recovery of superconductivity within the cores. Our numerical calculations combined with experiments clarify that these characteristic features are determined by the relative strength of the interterrace Josephson coupling at the atomic step.

Current-Driven Supramolecular Motor with In Situ Surface Chiral Directionality Switching

Surface-supported molecular motors are nanomechanical devices of particular interest in terms of future nanoscale applications. However, the molecular motors realized so far consist of covalently bonded groups that cannot be reconfigured without undergoing a chemical reaction. Here we demonstrate that a platinum-porphyrin-based supramolecularly assembled dimer supported on a Au(111) surface can be rotated with high directionality using the tunneling current of a scanning tunneling microscope (STM). Rotational direction of this molecular motor is determined solely by the surface chirality of the dimer, and most importantly, the chirality can be inverted in situ through a process involving an intradimer rearrangement. Our result opens the way for the construction of complex molecular machines on a surface to mimic at a smaller scale versatile biological supramolecular motors.

Anti-phase modulation of electron-and hole-like states in vortex core of Bi2Sr2CaCu2Ox probed by scanning tunneling spectroscopy

In the vortex core of slightly overdoped Bi 2 Sr 2 CaCu 2 O x , the electron- and hole-like states have been found to exhibit spatial modulations in anti-phase with each other along the Cu–O bonding direction. Some kind of one-dimensionality has been observed in the vortex core, and it is more clearly seen in differential conductance maps at lower biases below ±9 mV.

High-Resolution Scanning Tunneling Spectroscopy of Vortex Cores in Inhomogeneous Electronic States of Bi2Sr2CaCu2Ox

We studied electronic states in vortex cores of slightly overdoped Bi2Sr2CaCu2Ox by scanning tunneling spectroscopy. We have found that they have stripe structures with a \(4a_{0}\) width extending along the Cu–O bond directions. Vortex core states are observed as two peaks at particle–hole symmetric positions in the energy gap. Along a stripe, the peak positions of vortex core states are constant and not influenced by the spatial variation of the energy gap Δ. Outer stripes have a larger energy than inner stripes. A mazelike pattern in the electronic states at \(E = \pm\Delta\) has been observed all over the surface both inside and outside the vortex core. The orientation of stripes of vortex core states was found to be related to the mazelike pattern in the vortex core region. A short-range order of the mazelike pattern spatially coexists with the superconductivity and locally breaks the symmetry of the two Cu–O bond directions. We propose that the vortex core bound states are formed by Bogoliubov quasi...

Disorder-induced suppression of superconductivity in theSi(111)−(7×3)-In surface: Scanning tunneling microscopy study

The critical effect of disorder on the two-dimensional (2D) surface superconductor Si(111)-(

Controlled Modification of Superconductivity in Epitaxial Atomic Layer-Organic Molecule Heterostructures

\sqrt{7}\times\sqrt{3}

Excitation spectrum of Josephson vortices on surface superconductor

)-In is clarified by comparing two regions with different degrees of disorder. Low-temperature scanning tunneling microscopy measurements reveal that superconductivity is retained in the less disordered region, judging from the characteristic differential conductance (

Scanning tunneling spectroscopy study of quasiparticle interference on the dual topological insulatorBi1−xSbx

dI/dV

Ultrafast vibrational energy transfer from photoexcited carbon nanotubes to protein

) spectra and from the formation of vortices under magnetic fields. In striking contrast, the absence of those features in the highly disordered region shows that superconductivity is strongly suppressed there. Analysis of observed zero-bias anomalies in