ISSP - The institute for Solid State Physics

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Uwatoko Group

Research Associate

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The high-pressure group has been studying various materials under high-pressure conditions in combination with low temperature and/or strong magnetic field. Nowadays, the techniques combining these multi-extreme conditions have become popular and indispensable for researches in solid state physics. However, the developments of these techniques that can realize in-situ measurements under multiple extreme conditions are often challenging and require sophisticated considerations. This group has devoted numerous efforts in developing such advanced high-pressure techniques and in studying the strongly correlated electronic systems, which is one of the most important themes in modern solid state physics. Considering the fact that many mysterious phenomena in strongly correlated electronic systems result from the electron-phonon and electron-electron interactions, we foresee the discovery of many unknown phenomena under multi-extreme conditions because high pressure offers an effective knob in tuning the inter-atomic distances and the density of electronic state that controls the degree of complex interactions.

MnP is ferromagnetic between Tc ≈ 291 K and Ts ≈ 50 K, which adopts an orthorhombic B31-type structure with space group Pnma. A temperature-pressure phase diagram is shown in this figure. With the application of external pressure, (1) both ferromagnetic (Tc) and antiferromagnetic (Ts; helical-c structure) transitions decrease, and Ts vanishes completely around 1.4 GPa; (2) a new antiferromagnetic (T*; helical-b structure) transition appears around 2 GPa, rises quickly, and merges with Tc around 3-4 GPa at Tm; (3) Tm, helical-b structure, is continuously suppressed and eventually vanishes around Pc = 8 GPa, where superconductivity with a maximum Tsc ≈ 1K is observed. Exotic physical properties associated with the magnetic quantum critical point at Pc are evidenced. This is the first discovery of superconductivity among the Mn-based compounds.

Research Subjects

  1. Search for new physical phenomena under multi extreme conditions
  2. Study of the pressure induced phase transition phenomena as like superconductivity
  3. Development of high pressure apparatus and confirmation of physical property measurement techniques under the multi extreme conditions