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    20 December 2022, Volume 42 Issue 6 Previous Issue    Next Issue

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    Pressure-Induced Superconducting and Topological Phase Transitions in the RuX2 (X=P, As, Sb) Family Compounds
    CHEN Qun , WU Jue-fei , WANG Xiao-meng , DING Chi, HUANG Tian-heng , LU Qing , SUN Jian
    2022, 42 (6):  195-206.  doi: 10.13725/j.cnki.pip.2022.06.001
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    RuSb2, as a sister material of thermoelectric material FeSb2, has been extensively studied focusing on the comparisons with FeSb2, however, the properties of RuSb2 under pressure have not been surveyed thoroughly yet. In this work, we studied the properties of RuSb2 under pressure and explored the similarities and differences of crystal and electronic structures between the Ru-pnictides partners RuP2 and RuAs2. Using the crystal structures search method together with first-principles calculations, we found that this family undergoes a serial of structural phase transitions: (I) For RuSb2: PnnmI4/mcmI4/mmm; (II) for RuP2: PnnmI41/amd → Cmcm; (III) for RuAs2: Pnnm → P-62m. The newly found five phases are all energetically and dynamically stable at high-pressure and exhibit metallic properties. The four high pressure phases of RuSb2 and RuP2 can be quenched to zero pressure. The superconducting transition temperatures of I4/mcm and I4/mmm phases of RuSb2 and I41/amd and Cmcm phase of RuP2 are predicted to be approximately 7.3 K, 10.9 K, 13.0 K, and 10.1 K at 0 GPa, respectively. In addition, the I4/mcm and I4/mmm phases of RuSb2 and the I41/amd phase of RuP2 exhibit non-trivial topological properties. Our studies illustrate that pressure is an effective way to tune the structural, electronic, and superconducting behavior of the Ru-pnictides compounds.

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    Thermal Transport Measurements in Strongly Correlated Electronic Systems 
    CHENG Shu-fan , XU Hao , BAO Song , WEN Jin-sheng
    2022, 42 (6):  207-231.  doi: 10.13725/j.cnki.pip.2022.06.002
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    When taking into account the electronic correlations such as the onsite Coulomb repulsion and coupling between electrons, spins and orbitals, many fascinating novel quantum states beyond the free-electron framework can emerge, e.g., unconventional superconductiviity and quantum spin liquids. The understanding of these new states not only will expand the existing territory of our knowledge, but also likely lead to revolution in quantum science and technology. Therefore, studying the strongly correlated physics is a cutting-edge theme in condensed matter physics. The parent state of cuprate high-temperature superconductors is a Mott insulator, an insulating state due to the strong electronic correlation, whereas the band theory predicts it to be metallic. Due to the Coulomb gap in Mott insulators, the charge degree of freedom is often frozen, which makes electrical transport measurements inapplicable. As a probe sensitive to the elementary excitations of quasiparticles not limited to electrons, but also including magnons, spinons, as well as phonons, thermal transport measurements play an important role in the study of strongly correlated electronic systems. In this paper, we review some of the recent interesting results on unconventional superconductors, heavy fermions and quantum spin liquids utilizing the longitudinal thermal transport measurements, complimentary to our recent review article on the progress of the transverse thermal conductivity measurements on the thermal Hall effect. 

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