@article{10863, abstract = {Nonlinear optical responses are commonly used as a probe for studying the electronic properties of materials. For topological materials, studies thus far focused on photogalvanic electric currents, which are forbidden in centrosymmetric materials because they require broken inversion symmetry. In this Letter, we propose a class of symmetry-allowed responses for inversion-symmetric topological insulators with two doubly degenerate bands. We consider a specific example of such a response, the orbital current, and show that the sign of the response reflects the Z2 topological index, i.e., the orbital current changes sign at the transition between trivial and topological insulator phases. This is illustrated in two models of topological insulators: the Bernevig-Hughes-Zhang model and the 1T′ phase of transition metal dichalcogenides.}, author = {Davydova, Margarita and Serbyn, Maksym and Ishizuka, Hiroaki}, issn = {2469-9969}, journal = {Physical Review B}, publisher = {American Physical Society}, title = {{Symmetry-allowed nonlinear orbital response across the topological phase transition in centrosymmetric materials}}, doi = {10.1103/PhysRevB.105.L121407}, volume = {105}, year = {2022}, } @article{6369, abstract = {We construct a metamaterial from radio-frequency harmonic oscillators, and find two topologically distinct phases resulting from dissipation engineered into the system. These phases are distinguished by a quantized value of bulk energy transport. The impulse response of our circuit is measured and used to reconstruct the band structure and winding number of circuit eigenfunctions around a dark mode. Our results demonstrate that dissipative topological transport can occur in a wider class of physical systems than considered before.}, author = {Rosenthal, Eric I. and Ehrlich, Nicole K. and Rudner, Mark S. and Higginbotham, Andrew P and Lehnert, K. W.}, issn = {2469-9950}, journal = {Physical Review B}, number = {22}, publisher = {American Physical Society (APS)}, title = {{Topological phase transition measured in a dissipative metamaterial}}, doi = {10.1103/physrevb.97.220301}, volume = {97}, year = {2018}, } @article{9065, abstract = {Magnetic anisotropy in strontium iridate (Sr2IrO4) is found to be large because of the strong spin-orbit interactions. In our work, we studied the in-plane magnetic anisotropy of Sr2IrO4 and traced the anisotropic exchange interactions between the isospins in the crystal. The magnetic-field-dependent torque τ(H) showed a prominent transition from the canted antiferromagnetic state to the weak ferromagnetic (WFM) state. A comprehensive analysis was conducted to examine the isotropic and anisotropic regimes and probe the easy magnetization axis along the a b plane. The angle-dependent torque τ(θ) revealed a deviation from the sinusoidal behavior, and small differences in hysteresis were observed around 0° and 90° in the low-magnetic-field regime. This indicates that the orientation of the easy axis of the FM component is along the b axis, where the antiferromagnetic to WFM spin-flop transition occurs. We compared the coefficients of the magnetic susceptibility tensors and captured the anisotropy of the material. The in-plane τ(θ) revealed a tendency toward isotropic behavior for fields with values above the field value of the WFM transition.}, author = {Nauman, Muhammad and Hong, Yunjeong and Hussain, Tayyaba and Seo, M. S. and Park, S. Y. and Lee, N. and Choi, Y. J. and Kang, Woun and Jo, Younjung}, issn = {2469-9950}, journal = {Physical Review B}, number = {15}, publisher = {American Physical Society}, title = {{In-plane magnetic anisotropy in strontium iridate Sr2IrO4}}, doi = {10.1103/physrevb.96.155102}, volume = {96}, year = {2017}, }