Cao Junzhi, Liang Sihang, Zhang Cheng, Liu Yanwen, Huang Junwei, Jin Zhao, Chen Zhi-Gang, Wang Zhijun, Wang Qisi, Zhao Jun, Li Shiyan, Dai Xi, Zou Jin, Xia Zhengcai, Li Liang, Xiu Faxian
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China.
Nat Commun. 2015 Jul 13;6:7779. doi: 10.1038/ncomms8779.
Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac materials that exhibit linear energy dispersion in the bulk and can be viewed as three-dimensional graphene. It has been proposed that TDSs can be driven to other exotic phases like Weyl semimetals, topological insulators and topological superconductors by breaking certain symmetries. Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry. The detected Berry phase develops an evident angular dependence and possesses a crossover from non-trivial to trivial state under high magnetic fields, a strong hint for a fierce competition between the orbit-coupled field strength and the field-generated mass term. Our results unveil the important role of symmetry breaking in TDSs and further demonstrate a feasible path to generate a Weyl semimetal phase by breaking time reversal symmetry.
三维拓扑狄拉克半金属（TDSs）是一种新型狄拉克材料，其体内呈现线性能量色散，可被视为三维石墨烯。有人提出，通过打破某些对称性，TDSs可被驱动至其他奇异相，如外尔半金属、拓扑绝缘体和拓扑超导体。在此，我们报告了在强磁场下对TDS Cd3As2单晶中朗道能级分裂进行的首次输运实验，表明通过打破时间反演对称性可消除自旋简并。检测到的贝里相位呈现明显的角度依赖性，并且在强磁场下具有从非平凡态到平凡态的转变，这强烈暗示了轨道耦合场强与场致质量项之间的激烈竞争。我们的结果揭示了对称性破缺在TDSs中的重要作用，并进一步证明了通过打破时间反演对称性来产生外尔半金属相的可行途径。
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