A He-activated loading-cell for uniaxial pressure experiments is presented. The cell is based on a He bellow with a piezo force sensor and anvils. The uniaxial pressure is varied at low temperature by tuning the He gas pressure outside of the cryostat. Three experimental results under uniaxial pressure are demonstrated, that is, reentant superconductivity in ferromagnetic superconductor URhGe, uniaxial pressure tuned “hidden order” and antiferromagnetism in URu2Si2, and uniaxial pressure induced ferromagnetism in UCoAl.
In this article, we review the effect of strain on an organic field effect transistor with superconducting channel. Molecular conductors laminated on substrates experience significant biaxial strain via thermal contraction of the substrates, resulting in the electronic phase transitions at low temperatures. Furthermore, bending of the substrate enables continuous control of uniaxial strain without a pressure medium. This method in combination with field-effect doping allows one to investigate the superconducting phase diagram in the effective bandfilling-bandwidth parameter space.
In this article, uniaxial-stress effects on spin-driven multiferroics and magnetic skyrmion materials are reviewed. In both systems, symmetries of magnetic and crystal structures are closely related to cross-correlated phenomena such as magnetically induced electric polarization and unconventional Hall effect induced by non-coplanar magnetic order. An application of uniaxial stress is one of the most primitive ways to control the symmetry of matter. We have developed uniaxial stress cells, and have demonstrated that the magnetic phase transitions and resulting cross-correlated phenomena in multiferroics and magnetic skyrmion systems can be controlled by applying a relatively weak uniaxial stress.
Application of strain is one of the effective ways to tailor physical properties of materials through the control of the band structure. In this article, a focus is on biaxial strain applied on single-crystalline samples. Transport measurements were performed on FeSe single crystals with various degrees of in-plane biaxial strain, which was introduced by firmly gluing samples to various substrate materials with different thermal expansion. The analysis of magnetotransport results revealed a systematic change in the carrier density with strain. This indicates that the band structure of FeSe single crystals was definitely controlled by biaxial strain.
In the iron-based superconductors, elastoresistance has successfully explored the anisotropic electronic instability associated with nematic order, recognized as nematic susceptibility. This article reviews the techniques of elastoresistance measurements using the piezoelectric actuators and the behaviors of nematic susceptibility in various iron-based superconductors, including FeSe1－xSx, hole-doped BaFe2As2 system, and the iron-ladder materials BaFe2S3. In addition, we report non-linear strain dependence of resistivity anisotropy inside the nematic phase revealed by applying the large strain using the platform techniques.
Recent invention of uniaxial-strain application devices using piezo-electric stacks triggered various innovations in condensed-matter physics, providing a unique tool to directly control in situ the crystalline symmetry. In this review, we describe features and usage of piezo-based uniaxial strain devices. We also explain our recent study on the uniaxial-strain study on nematic superconductivity, liquid-crystal-like superconductivity, which was recently found in doped Bi2Se3 superconductors. By applying 1% compressive in-plane strain to Sr-doped Bi2Se3, the configuration of nematic superconducting domains has been successfully controlled.