Hydrostatic pressure effect on new BiS 2 based Bi 4 O 4 S 3 and ReO/FBiS 2 (Re = La, Pr, Nd, Sm) Superconductors
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Hydrostatic pressure effect on new BiS2 based Bi4O4S3 and ReO/FBiS2 (Re = La, Pr, Nd, Sm) Superconductors Sonachalam Arumugam1 and Ganesan Kalai Selvan2 1 Centre for High Pressure Research, School of Physics, Bharathidasan University Tiruchirappalli, Tamil Nadu-620 024, India.
ABSTRACT Discovery of superconductivity in BiS2 layers based systems has attracted tremendous interest of both experimentalists and theoreticians from condensed matter physics community. In this article, a review of our high pressure studies on BiS2 based superconductors is given. The pressure effects on magnetic, transport properties and superconducting transitions are discussed for different types of doped and undoped BiS2-based compounds such as Bi4O4S3 and ReO/FBiS2 (Re = rare-earth). Pressure tends to decrease the magnetic transition temperature in the undoped or only slightly doped compounds. The superconducting Tc increases with low pressure for under doped BiS2 based compounds, remains approximately constant for optimal doping, and decreases linearly in the overdoped range. Under pressure, the semiconducting behavior in the normal state is suppressed markedly and monotonically, whereas the evolution of Tc is nonlinear, the superconductivity in the BiS2 layer favors the Fermi surface at the boundary between the semiconducting and metallic behaviors. However, strong suppression of the semiconducting and induced metallic behavior without doping in ReO/FBiS2 suggests that the Fermi surface is located in the vicinity of some instability. Furthermore, notable properties under pressure in the BiS2 family are reported. The prospects for raising Tc in this family are proposed on the basis of experimental and theoretical studies. INTRODUCTION Majorities of interactions in solids (and other states of matter) depend critically on the inter-atomic distance. The application of pressure changes the inter-atomic distance and modifies the electronic and the phononic energy spectra of a solid without introducing any chemical complexity and keeping the physical complexity to a minimum. Therefore, high pressure techniques have been extensively used in recent years to explore the physical states of solids, to create new ground states in solids, to test theoretical models and to help develop new theories. For example, there are more nonsuperconducting elements that have been turned into superconductors through the application of pressure in the last half-century than naturally occurring elemental superconductors [1]. It was the high pressure experiments on the A15 compound system to examine the correlation between superconductivity and lattice instabilities in the late 1970s and early 1980s that gave us the confidence that superconductivity could take place at temperatures above 30 K [2], in contrast to the then theoretical prediction [3]. Again, it was the high pressure experiments on cuprates demonstrated that indeed a superconducting transition temperature (Tc) could be achieved above 50 K and suggested that the cuprate system warranted further explorat
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