Superconductivity is one of the most intriguing topics in solid state physics. In general, spin-singlet Cooper pairs in superconducting phases are broken by the Zeeman effect, which gives the Pauli limit. However, Cooper pairs can theoretically survive even above the Pauli limit in special conditions, which is the so-called FFLO phase. So fat, extensive efforts have been devoted to the discovery of the FFLO phase but vortex melting transitions have given rise to considerable ambiguity in the interpretation of the experimental data. By comprehensive magnetocaloric and torque studies of the FFLO phase in a highly two-dimensional organic superconductor, the FFLO phase transition is observed near the Pauli limit, clearly distinct from the vortex melting transitions. The results provide convincing evidence of the FFLO phase in high magnetic fields.
We investigated information spreading on online social media, which is widely used in Japan. In particular, we constructed an index for information spreading on Twitter, focusing on the difference in network structure between fake news and real news. This index may enable us to extract the difference between fake and real news without text or demographic information.
We introduce some recent progress on the friction at extremely large sliding velocities. We first explain our experimental results using compliant polymer gels, where we find a transition in friction and deformation at sliding velocities above the Secondary wave velocity. Then we discuss theoretical development; analytical solutions for the deformation and stress fields between a semi-infinite isotropic elastic medium and a rigid cylindrical indenter during steady sliding. Based on the comparisons between experiment and theory, we validate the theoretical results. Finally, we raise several important topics to be studied as future problems.
Ferroelectric material has been considered a typical insulator due to its high resistivity and wide optical bandgap, which we learned in textbooks. Here we show that ferroelectrics have a skewed electronic band structure strongly correlating with an electric polarization. Such a specific electronic structure can modulate the valence state of the neighboring metal. The fact will open the door to new methodologies of ferroelectric science.
Rectification effect, which represents that forward and backward current in solids becomes inequivalent, has been conventionally discussed in semiconductor p–n junction or metal-semiconductor interface. However, it was recently discovered that the intrinsic rectification effect or nonreciprocal transport can occur even in transrational symmetric crystals without inversion center. Such rectification effect inherent in noncentrosymmetric solids reflect the peculiar electronic structures, geometrical or topological properties of the wave function, and spin/charge dynamics. Here we report the systematic studies of the intrinsic rectification effect under the magnetic field in a variety of noncentrosymmetric quantum materials. It is clarified that intrinsic rectification effect can provide rich information of electronic band structure such as spin-orbit interaction, superconducting fluctuation and vortex dynamics, thus being a powerful probe for exotic quantum phases of matters.