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Johnson PA, Limacher PA, Kim TD, Richer M, Miranda-Quintana RA, Heidar-Zadeh F, Ayers PW, Bultinck P, De Baerdemacker S, Van Neck D. Strategies for extending geminal-based wavefunctions: Open shells and beyond. COMPUT THEOR CHEM 2017. [DOI: 10.1016/j.comptc.2017.05.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Topological phase transition in quasi-one dimensional organic conductors. Sci Rep 2015; 5:17358. [PMID: 26612317 PMCID: PMC4661575 DOI: 10.1038/srep17358] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/28/2015] [Indexed: 11/09/2022] Open
Abstract
We explore topological phase transition, which involves the energy spectra of field-induced spin-density-wave (FISDW) states in quasi-one dimensional (Q1D) organic conductors, using an extended Su-Schrieffer-Heeger (SSH) model. We show that, in presence of half magnetic-flux FISDW state, the system exhibits topologically nontrivial phases, which can be characterized by a nonzero Chern number. The nontrivial evolution of the bulk bands with chemical potential in a topological phase transition is discussed. We show that the system can have a similar phase diagram which is discussed in the Haldane's model. We suggest that the topological feature should be tested experimentally in this organic system. These studies enrich the theoretical research on topologically nontrivial phases in the Q1D lattice system as compared to the Haldane topological phase appearing in the two-dimensional lattices.
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Abstract
Hybrid architectures, consisting of conventional and topological qubits, have recently attracted much attention due to their capability in consolidating robustness of topological qubits and universality of conventional qubits. However, these two kinds of qubits are normally constructed in significantly different energy scales, and thus the energy mismatch is a major obstacle for their coupling, which can support the exchange of quantum information between them. Here we propose a microwave photonic quantum bus for a strong direct coupling between the topological and conventional qubits, where the energy mismatch is compensated by an external driving field. In the framework of tight-binding simulation and perturbation approach, we show that the energy splitting of Majorana fermions in a finite length nanowire, which we use to define topological qubits, is still robust against local perturbations due to the topology of the system. Therefore, the present scheme realizes a rather robust interface between the flying and topological qubits. Finally, we demonstrate that this quantum bus can also be used to generate multipartitie entangled states with the topological qubits.
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Affiliation(s)
- Zheng-Yuan Xue
- 1] Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, and School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China [2] Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Ming Gong
- Department of Physics and Center for Quantum Coherence, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Jia Liu
- Department of Physics and Center for Quantum Coherence, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
| | - Yong Hu
- 1] Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China [2] School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Shi-Liang Zhu
- 1] National Laboratory of Solid State Microstructure and School of Physics, Nanjing University, Nanjing 210093, China [2] Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Z D Wang
- Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China
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Dynamical phases in quenched spin-orbit-coupled degenerate Fermi gas. Nat Commun 2015; 6:6103. [PMID: 25600665 DOI: 10.1038/ncomms7103] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 12/12/2014] [Indexed: 11/08/2022] Open
Abstract
The spin-orbit-coupled degenerate Fermi gas provides a new platform for realizing topological superfluids and related topological excitations. However, previous studies have been mainly focused on the topological properties of the stationary ground state. Here, we investigate the quench dynamics of a spin-orbit-coupled two-dimensional Fermi gas in which the Zeeman field serves as the major quench parameter. Three post-quench dynamical phases are identified according to the asymptotic behaviour of the order parameter. In the undamped phase, a persistent oscillation of the order parameter may support a topological Floquet state with multiple edge states. In the damped phase, the magnitude of the order parameter approaches a constant via a power-law decay, which may support a dynamical topological phase with one edge state at the boundary. In the overdamped phase, the order parameter decays to zero exponentially although the condensate fraction remains finite. These predictions can be observed in the strong-coupling regime.
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Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases. Sci Rep 2014; 4:5218. [PMID: 24918901 PMCID: PMC4052715 DOI: 10.1038/srep05218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 05/19/2014] [Indexed: 11/08/2022] Open
Abstract
We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally.
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Fu HH, Gao JH, Yao KL. Topological field-effect quantum transistors in HgTe nanoribbons. NANOTECHNOLOGY 2014; 25:225201. [PMID: 24806590 DOI: 10.1088/0957-4484/25/22/225201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We propose practical designs to realize topological field-effect quantum transistors in an HgTe nanoribbon with an inverted band structure. Our theoretical calculations show that, as a strip-shape top gate is placed on the HgTe nanoribbon and with an increasing gate voltage, two new conductance channels develop in the HgTe nanoribbon and are localized to the lattice sites neighboring the boundaries of the gate, leading to an additional quantization of the conductance of 2e(2)/h. The quantum states in the new channels are not only robust against a short-range Anderson disorder, but can also couple with the intrinsic helical edge states in the boundaries of the HgTe nanoribbon to open a gap in the energy spectrum, indicating their topological characteristics. More importantly, the newly developed conductance channels can be turned on or off easily by adjusting the gate voltage. The proposal of controllable topological edge states produced by the gate voltage opens a new route for future topological field-effect quantum transistors in nanoelectronics and spintronics.
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Affiliation(s)
- Hua-Hua Fu
- Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China. Wuhan National High Magnetic field center, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
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