Browsing by Author "Yan, Han"
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Item Magnetic field effects in an octupolar quantum spin liquid candidate(American Physical Society, 2022) Gao, Bin; Chen, Tong; Yan, Han; Duan, Chunruo; Huang, Chien-Lung; Yao, Xu Ping; Ye, Feng; Balz, Christian; Stewart, J. Ross; Nakajima, Kenji; Ohira-Kawamura, Seiko; Xu, Guangyong; Xu, Xianghan; Cheong, Sang-Wook; Morosan, Emilia; Nevidomskyy, Andriy H.; Chen, Gang; Dai, PengchengQuantum spin liquid (QSL) is a disordered state of quantum-mechanically entangled spins commonly arising from frustrated magnetic dipolar interactions. However, QSL in some pyrochlore magnets can also come from frustrated magnetic octupolar interactions. Although the key signature for both dipolar and octupolar interaction-driven QSL is the presence of a spin excitation continuum (spinons) arising from the spin quantum number fractionalization, an external magnetic field-induced ferromagnetic order will transform the spinons into conventional spin waves in a dipolar QSL. By contrast, in an octupole QSL, the spin waves carry octupole moments that do not couple, in the leading order, to an external magnetic field or to neutron moments but will contribute to the field dependence of the heat capacity. Here we use neutron scattering to show that the application of a large external magnetic field to Ce2Zr2O7, an octupolar QSL candidate, induces an Anderson-Higgs transition by condensing the spinons into a static ferromagnetic ordered state with octupolar spin waves invisible to neutrons but contributing to the heat capacity. Our theoretical calculations also provide a microscopic, qualitative understanding for the presence of octupole scattering at large wave vectors in Ce2Sn2O7 pyrochlore, and its absence in Ce2Zr2O7. Therefore, our results identify Ce2Zr2O7 as a strong candidate for an octupolar U(1) QSL, establishing that frustrated magnetic octupolar interactions are responsible for QSL properties in Ce-based pyrochlore magnets.Item Sleuthing out exotic quantum spin liquidity in the pyrochlore magnet Ce2Zr2O7(Springer Nature, 2022) Bhardwaj, Anish; Zhang, Shu; Yan, Han; Moessner, Roderich; Nevidomskyy, Andriy H.; Changlani, Hitesh J.The search for quantum spin liquids—topological magnets with fractionalized excitations—has been a central theme in condensed matter and materials physics. Despite numerous theoretical proposals, connecting experiment with detailed theory exhibiting a robust quantum spin liquid has remained a central challenge. Here, focusing on the strongly spin-orbit coupled effective S = 1/2 pyrochlore magnet Ce2Zr2O7, we analyze recent thermodynamic and neutron-scattering experiments, to identify a microscopic effective Hamiltonian through a combination of finite temperature Lanczos, Monte Carlo, and analytical spin dynamics calculations. Its parameter values suggest the existence of an exotic phase, a π-flux U(1) quantum spin liquid. Intriguingly, the octupolar nature of the moments makes them less prone to be affected by magnetic disorder, while also hiding some otherwise characteristic signatures from neutrons, making this spin liquid arguably more stable than its more conventional counterparts.