Finding materials exhibiting superconductivity at room temperature has long been one of the ultimate goals in physics and material science.Recently,room-temperature superconducting properties have been claimed in a co...Finding materials exhibiting superconductivity at room temperature has long been one of the ultimate goals in physics and material science.Recently,room-temperature superconducting properties have been claimed in a copper substituted lead phosphate apatite(Pb_(10-x)Cu_(x)(PO_(4))_(6)O,or called LK-99)(Lee et al.in J.Korean Cryst.Growth Cryst.Technol.33:61,2023;Lee et al.in The first room-temperature ambient-pressure superconductor,2023;Lee et al.in Superconductor Pb_(10-x)Cu_(x)(PO_(4))_(6)O showing levitation at room temperature and atmospheric pressure and mechanism,2023).Using a similar approach,we have prepared LK-99 like samples and confirmed the half-levitation behaviors in some small specimens under the influence of a magnet at room temperature.To examine the magnetic properties of our samples,we have performed systematic magnetization measurements on the as-grown LK-99 like samples,including the half-levitated and non-levitated samples.The magnetization measurements show the coexistence of soft-ferromagnetic and diamagnetic signals in both half-levitated and non-levitated samples.The electrical transport measurements on the as-grown LK-99 like samples including both half-levitated and non-levitated samples show an insulating behavior characterized by the increasing resistivity with the decreasing temperature.展开更多
The resistivity-temperature(ρ(T))curve is traditionally employed to distinguish metallic,semiconducting,and insulating behaviors in materials,with deviations often interpreted as evidence of phase transitions.However...The resistivity-temperature(ρ(T))curve is traditionally employed to distinguish metallic,semiconducting,and insulating behaviors in materials,with deviations often interpreted as evidence of phase transitions.However,such interpretations are valid only under specific conditions,including the presence of a magnetic field.This study critically reexamines the ρ(T)curve in magnetic environments.Our findings reveal that shifts between metallic and insulating states,as well as reentrant metallic behavior,may not necessarily indicate genuine phase transitions.Instead,these phenomena can be attributed to the scaling behavior of magnetoresistance,governed by a power law dependence on both the magnetic field and temperature.Employing first-principles calculations and the Boltzmann transport method,we analyzed the magnetoresistance of SiP2 and NbP across varying conditions.This approach not only explains the reentrant behavior observed experimentally but also reconciles discrepancies in magnetoresistance findings reported by different research groups.These findings challenge the conventional reliance on the ρ(T)curve as a straightforward indicator of phase transitions in magnetic fields.We underscore the importance of accounting for standard magnetoresistance effects caused by the Lorentz force before confirming the existence of such transitions.This novel perspective advances our understanding of material properties in magnetic fields and establishes a new framework for interpreting transport phenomena in condensed matter physics.展开更多
基金funding provided by Shanghai Jiao Tong Universityfinancially supported by the National Natural Science Foundation of China(Grant No.11888101)the Innovation Program for Quantum Science and Technology(2021ZD0302403).
文摘Finding materials exhibiting superconductivity at room temperature has long been one of the ultimate goals in physics and material science.Recently,room-temperature superconducting properties have been claimed in a copper substituted lead phosphate apatite(Pb_(10-x)Cu_(x)(PO_(4))_(6)O,or called LK-99)(Lee et al.in J.Korean Cryst.Growth Cryst.Technol.33:61,2023;Lee et al.in The first room-temperature ambient-pressure superconductor,2023;Lee et al.in Superconductor Pb_(10-x)Cu_(x)(PO_(4))_(6)O showing levitation at room temperature and atmospheric pressure and mechanism,2023).Using a similar approach,we have prepared LK-99 like samples and confirmed the half-levitation behaviors in some small specimens under the influence of a magnet at room temperature.To examine the magnetic properties of our samples,we have performed systematic magnetization measurements on the as-grown LK-99 like samples,including the half-levitated and non-levitated samples.The magnetization measurements show the coexistence of soft-ferromagnetic and diamagnetic signals in both half-levitated and non-levitated samples.The electrical transport measurements on the as-grown LK-99 like samples including both half-levitated and non-levitated samples show an insulating behavior characterized by the increasing resistivity with the decreasing temperature.
基金supported by the National Key R&D Programof China(2023YFA1607400 and 2022YFA1403800)the National Natural Science Foundation of China(12274436,11925408,and 11921004),and the Science Center of the National Natural Science Founda-tion of China(12188101)support from the New Cornerstone Sci-ence Foundation through the XPLORER PRIZE.
文摘The resistivity-temperature(ρ(T))curve is traditionally employed to distinguish metallic,semiconducting,and insulating behaviors in materials,with deviations often interpreted as evidence of phase transitions.However,such interpretations are valid only under specific conditions,including the presence of a magnetic field.This study critically reexamines the ρ(T)curve in magnetic environments.Our findings reveal that shifts between metallic and insulating states,as well as reentrant metallic behavior,may not necessarily indicate genuine phase transitions.Instead,these phenomena can be attributed to the scaling behavior of magnetoresistance,governed by a power law dependence on both the magnetic field and temperature.Employing first-principles calculations and the Boltzmann transport method,we analyzed the magnetoresistance of SiP2 and NbP across varying conditions.This approach not only explains the reentrant behavior observed experimentally but also reconciles discrepancies in magnetoresistance findings reported by different research groups.These findings challenge the conventional reliance on the ρ(T)curve as a straightforward indicator of phase transitions in magnetic fields.We underscore the importance of accounting for standard magnetoresistance effects caused by the Lorentz force before confirming the existence of such transitions.This novel perspective advances our understanding of material properties in magnetic fields and establishes a new framework for interpreting transport phenomena in condensed matter physics.
