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Simulation of Hubbard model physics in WSe2/WS2 moire superlattices 期刊论文
NATURE, 2020, 579 (7799) : 353-+
作者:  Stein, Reed M.;  Kang, Hye Jin;  McCorvy, John D.;  Glatfelter, Grant C.;  Jones, Anthony J.;  Che, Tao;  Slocum, Samuel;  Huang, Xi-Ping;  Savych, Olena;  Moroz, Yurii S.;  Stauch, Benjamin;  Johansson, Linda C.;  Cherezov, Vadim;  Kenakin, Terry;  Irwin, John J.;  Shoichet, Brian K.;  Roth, Bryan L.;  Dubocovich, Margarita L.
收藏  |  浏览/下载:34/0  |  提交时间:2020/07/03

Study of WSe2/WS2 moire superlattices reveals the phase diagram of the triangular-lattice Hubbard model, including a Mott insulating state at half-filling and a possible magnetic quantum phase transition near 0.6 filling.


The Hubbard model, formulated by physicist John Hubbard in the 1960s(1), is a simple theoretical model of interacting quantum particles in a lattice. The model is thought to capture the essential physics of high-temperature superconductors, magnetic insulators and other complex quantum many-body ground states(2,3). Although the Hubbard model provides a greatly simplified representation of most real materials, it is nevertheless difficult to solve accurately except in the one-dimensional case(2,3). Therefore, the physical realization of the Hubbard model in two or three dimensions, which can act as an analogue quantum simulator (that is, it can mimic the model and simulate its phase diagram and dynamics(4,5)), has a vital role in solving the strong-correlation puzzle, namely, revealing the physics of a large number of strongly interacting quantum particles. Here we obtain the phase diagram of the two-dimensional triangular-lattice Hubbard model by studying angle-aligned WSe2/WS2 bilayers, which form moire superlattices(6) because of the difference between the lattice constants of the two materials. We probe the charge and magnetic properties of the system by measuring the dependence of its optical response on an out-of-plane magnetic field and on the gate-tuned carrier density. At half-filling of the first hole moire superlattice band, we observe a Mott insulating state with antiferromagnetic Curie-Weiss behaviour, as expected for a Hubbard model in the strong-interaction regime(2,3,7-9). Above half-filling, our experiment suggests a possible quantum phase transition from an antiferromagnetic to a weak ferromagnetic state at filling factors near 0.6. Our results establish a new solid-state platform based on moire superlattices that can be used to simulate problems in strong-correlation physics that are described by triangular-lattice Hubbard models.


  
Entanglement of two quantum memories via fibres over dozens of kilometres 期刊论文
NATURE, 2020, 578 (7794) : 240-+
作者:  Cabrita, Rita;  Lauss, Martin;  Sanna, Adriana;  Donia, Marco;  Larsen, Mathilde Skaarup;  Mitra, Shamik;  Johansson, Iva;  Phung, Bengt;  Harbst, Katja;  Vallon-Christersson, Johan;  van Schoiack, Alison;  Loevgren, Kristina;  Warren, Sarah;  Jirstroem, Karin;  Olsson, Hakan;  Pietras, Kristian;  Ingvar, Christian;  Isaksson, Karolin;  Schadendorf, Dirk;  Schmidt, Henrik;  Bastholt, Lars;  Carneiro, Ana;  Wargo, Jennifer A.;  Svane, Inge Marie;  Jonsson, Goran
收藏  |  浏览/下载:54/0  |  提交时间:2020/07/03

A quantum internet that connects remote quantum processors(1,2) should enable a number of revolutionary applications such as distributed quantum computing. Its realization will rely on entanglement of remote quantum memories over long distances. Despite enormous progress(3-12), at present the maximal physical separation achieved between two nodes is 1.3 kilometres(10), and challenges for longer distances remain. Here we demonstrate entanglement of two atomic ensembles in one laboratory via photon transmission through city-scale optical fibres. The atomic ensembles function as quantum memories that store quantum states. We use cavity enhancement to efficiently create atom-photon entanglement(13-15) and we use quantum frequency conversion(16) to shift the atomic wavelength to telecommunications wavelengths. We realize entanglement over 22 kilometres of field-deployed fibres via two-photon interference(17,18) and entanglement over 50 kilometres of coiled fibres via single-photon interference(19). Our experiment could be extended to nodes physically separated by similar distances, which would thus form a functional segment of the atomic quantum network, paving the way towards establishing atomic entanglement over many nodes and over much longer distances.


  
Predictability and Quantification of Complex Groundwater Table Dynamics Driven by Irregular Surface Water Fluctuations 期刊论文
WATER RESOURCES RESEARCH, 2018, 54 (3) : 2436-2451
作者:  Xin, Pei;  Wang, Shen S. J.;  Shen, Chengji;  Zhang, Zeyu;  Lu, Chunhui;  Li, Ling
收藏  |  浏览/下载:22/0  |  提交时间:2019/04/09
surface water-groundwater interaction  hyporheic zone  hysteresis  dynamics  physical experiment  regression model