在9.5~ 13 T范围内的磁场作用下，在重费米子化合物YbRh $_2$ Si $_2$中观察到一系列热电势的强反常现象。我们确定这些功能与复杂的费米表面的这种化合物，即级联的Lifshitz拓扑转换的拓扑变换序列。为了毫无疑问地将这些异常归因于费米面的特定拓扑变化，我们采用重整化能带方法。在此基础上，我们提出了一个简化的模型，它由大的周边费米面片和连续出现（消失）的小“空洞”或“颈”的数量组成。我们占的费米面的各个组件之间的多个电子散射过程，计算相应的散射时间，并最终找到的磁场依赖的塞贝克系数。所得到的解析表达式合理地再现了观察到的位置的最大值和最小值以及整体线的形状，并允许我们识别相应的拓扑变换的字符。
英文摘要：
A series of strong anomalies in the thermoelectric power is observed in the heavy fermion compound YbRh$_2$Si$_2$ under the effect of magnetic field varying in the range from 9.5~T to 13~T. We identify these features with a sequence of topological transformations of the sophisticated Fermi surface of this compound, namely a cascade of Lifshitz topological transitions. In order to undoubtedly attribute these anomalies to the specific topological changes of the Fermi surface, we employ the renormalized band method. Basing on its results we suggest a simplified model consisting of the large peripheral Fermi surface sheet and the number of continuously appearing (disappearing) small "voids" or "necks". We account for the multiple electron scattering processes between various components of the Fermi surface, calculate the corresponding scattering times, and, finally, find the magnetic field dependence of the Seebeck coefficient. The obtained analytical expression reproduces reasonably the observed positions of the maxima and minima as well as the overall line shapes and allows us to identify the character of corresponding topological transformations.
High-pressure modulation of breathing kagome lattice: Cascade of Lifshitz transitions and evolution of the electronic structure
Helmholtz-Zentrum Dresden-Rossendorf（德累斯顿罗森多夫赫尔姆霍兹中心）；TUD Dresden University of Technology（德累斯顿工业大学）；Universität Stuttgart（斯图加特大学）；Synchrotron SOLEIL（索雷尔同步辐射中心）；ESRF（欧洲同步辐射装置）；ShanghaiTech University（上海科技大学）；Renmin University of China（中国人民大学）
Photostationary Lifshitz transition in High Tc superconductor Bi2Sr2CaCu2O8+δ
Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院物理研究所）；Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL)（洛桑超快科学中心）；LOREA, ALBA Synchrotron（ALBA同步辐射光源LOREA）；Dipartimento di Fisica, Politecnico di Milano（米兰理工大学物理系）；Department of Physics, Faculty of Science, University of Zagreb（萨格勒布大学理学院物理系）；Institute of Solid State Physics, TU Wien（维也纳工业大学固体物理研究所）；Department of Physics and Stavropoulos Center for Complex Quantum Matter, University of Notre Dame（圣母大学物理系及斯塔夫罗普洛斯复杂量子物质中心）；Laboratoire de Physique des Solides, Université Paris-Saclay（巴黎萨克雷大学固体物理实验室）
Link between superconductivity and a Lifshitz transition in intercalated Bi$_2$Se$_3$
拓扑超导是一种奇异的物质相，其中完全带隙的超导体具有拓扑保护的无带隙的马约拉纳表面态。在拓扑绝缘体Bi $_2$ Se $_3$的五重层之间插入铜、锶或铌增加了载流子密度并导致被认为是拓扑的超导性。本文利用角分辨光电子能谱（ARPES）和Shubnikov-de Haas（SdH）振荡研究了掺锶Bi $_2$ Se $_3$的电子结构。尽管明显的低霍尔数$\sim2 \times 10 ^{19}$ cm $^{-3}$，我们表明，费米面是一个开放的圆柱体形状与$\sim 10 ^{20}$ cm $^{-3}$较大的载流子密度。我们认为，超导电性在插入Bi $_2$ Se $_3$出现准二维开放费米面。
