The $z$-component of the Néel vector is measurable by the anomalous Hall conductivity in altermagnets because time reversal symmetry is broken. On the other hand, it is a nontrivial problem how to measure the in-plane component of the Néel vector. We study the second-order nonlinear conductivity of a system made of the $d$-wave altermagnet with the Rashba interaction. It is shown that the quantum-metric induced nonlinear conductivity and the nonlinear Drude conductivity are proportional to the in-plane component of the Néel vector, and hence, the in-plane component of the Néel vector is measurable. We obtain analytic formulas of the quantum-metric induced nonlinear conductivity and the nonlinear Drude conductivity both for the longitudinal and transverse conductivities. The quantum-metric induced nonlinear conductivity diverges at the Dirac point, while the nonlinear Drude conductivity is always finite. Hence, the quantum-metric induced nonlinear conductivity is dominant at the Dirac point irrespective of the relaxation time.
Quantum anomalous Hall conductivity in altermagnets under applied magnetic field
International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所）；Department of Physics, University of Guilan（吉尔兰大学物理系）；Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所）
Intrinsic Spin Filter Effect in a $d$-wave altermagnet KV$_2$Se$_2$O with Open Fermi Surface
School of Science, Sun Yat-sen University（中山大学理学院）；Department of Physics and Astronomy, University of Florence（佛罗伦萨大学物理与天文学系）；Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University（武汉大学物理科学与技术学院人工微结构和量子调控教育部重点实验室）；The State Key Laboratory for Refractories and Metallurgy, Wuhan University of Science and Technology（武汉科技大学耐火材料与冶金国家重点实验室）；Laboratory for Computational Physical Sciences (MOE), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University（复旦大学物理系表面物理国家重点实验室计算物理科学教育部重点实验室）；Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, Sun Yat-sen University（中山大学广东省磁电物理与器件重点实验室）
Circular phonon dichroism in $d$-wave altermagnets
Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院强磁场科学中心低能量子材料与器件安徽省重点实验室）；Department of Physics, University of Science and Technology of China（中国科学技术大学物理学院）；School of Physics and Optoelectronics Engineering, Anhui University（安徽大学物理与光电工程学院）
Functionalization of $g$-wave altermagnets: spin-splitter effect enabled by surfaces
Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology（量子材料与技术研究所，卡尔斯鲁厄理工学院）；Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology（理论固体物理研究所，卡尔斯鲁厄理工学院）
