arXiv subjects

Su-Peng Kou

Publications and source records attributed to Su-Peng Kou.

At least 73 records · Page 4Linked to original sources

arXiv2014

Topological Mid-gap States of px+ipy Topological Superconductor with Vortex superlattice

In this paper, the px+ipy topological superconductor with vortex superlattice is studied. We found that there exist mid-gap energy bands induced by the vortex superlattice and the mid-gap energy bands have nontrivial topological properties including the gapless edge states and non-zero winding number. An topological anisotropic tight-binding Majorana lattice model is proposed to describe the mid-gap states.

cond-mat.supr-con↗

arXiv2014

Strongly fluctuating fermionic superfluid in attractive π-flux Hubbard model

Ultracold atoms in optical lattice provides a platform to realize the superfluid (SF) state, a quantum order with paired charge-neutral fermions. In this paper, we studied SF state in the twodimensional attractive Hubbard model with pi-flux on each plaquette. The SF state in the pi-flux lattice model suffers very strong quantum fluctuations and the ground state becomes a possible quantum phase liquid state. In this phase, there exists the Cooper pairing together with a finite energy gap for the atoms, but no long range SF phase coherence exists at zero temperature. In addition, we discussed the properties of the SF vortices.

cond-mat.str-el↗

arXiv2014

Quantum Phase Liquids-Fermionic Superfluid without Phase Coherence

We investigate the two dimensional generalized attractive Hubbard model in a bipartite lattice, and and a "quantum phase liquid" phase, in which the fermions are paired but don't have phase coherence at zero temperature, in analogy to quantum spin liquid phase. Then, two types of topological quantum phase liquids with a small external magnetic field-Z2 quantum phase liquids and chiral quantum phase liquids-are discussed.

cond-mat.str-el↗

arXiv2013

Topological Mid-gap States of Topological Insulators with Flux-Superlattice

In this paper based on the Haldane model, we study the topological insulator with superlattice of pi-fluxes. We find that there exist the mid-gap states induced by the flux-superlattice. In particular, the mid-gap states have nontrivial topological properties, including the nonzero Chern number and the gapless edge states. We derive an effective tight-binding model to describe the topological midgap states and then study the mid-gap states by the effective tight-binding model. The results can be straightforwardly generalized to other two dimensional topological insulators with flux-superlattice.

cond-mat.str-el↗

arXiv2013

Magnetic Orders of Correlated Topological Insulators at Finite Temperature

In this paper, we study the magnetic orders of two dimensional correlated topological insulators including the correlated Chern insulator and the correlated Z2 topological insulator at finite temperature. For the 2D correlated Chern insulator, we found that thermal-fluctuation-induced magnetic order appears in the intermediate interaction region of the correlated Chern insulator. On the contrary, for the correlated Z2 topological insulator there doesn't exist the thermal-fluctuation-induced magnetic order. In the end, we give an explanation on the difference.

cond-mat.str-el↗

arXiv2013

Topological Superconductors in Correlated Chern Insulators

In this paper, we realize a topological superconductor (TSC) in correlated topological insulator - the interacting spinful Haldane model. We consider the electrons on the Haldane model with on-site negative-U interaction and then study its properties by mean field theory and random-phase-approximation (RPA) approach. We found that in the intermediate interaction region, the ground state becomes a TSC with the Chern number 2. We also study its edge states and the zero modes of the pi-flux.

cond-mat.supr-con↗

arXiv2013

Realizing Universal Majorana Fermionic Quantum Computation

Majorana-fermionic quantum computation (MFQC) was proposed by Bravyi and Kitaev (See Ref.\cite{Kitaev}), in which a fault-torrent (non-topological) quantum computer built from Majorana fermions may be more efficient than that built from distinguishable two-state systems. However, till now people don't know how to realize a MFQC in a physical system. In this paper we proposed a possible realization of MFQC. We find that the end of a line-defect of p-wave superconductor or superfluid on a honeycomb lattice will trap a Majorana zero mode, which will become the starting point of MFQC. Then we show how to manipulate Majorana fermions to do universal MFQC, which possesses unique possibilities for high-level local controllability, individual addressing, and readout of the quantum states of individual constituent elements by using timely cold-atom technology.

cond-mat.str-el↗

arXiv2012

Topological Majorana Lattice Model: Induced "Topological Superconductor" on Topological Superconductor with Vortex-lattice

In this paper we study an s-wave topological SC with a square vortex-lattice. We proposed a topological Majorana lattice model to describe this topological state. We found that the Majorana lattice model is really a "topological SC" on the parent topological SC. Such correspondence between the Majorana lattice model and the topological SC with vortex-lattice is another holographic feature of the topological state. In addition, the numerical calculations confirm our theoretical prediction.

cond-mat.supr-con↗

arXiv2012

Topological edge states in spin 1 bilinear-biquadratic model

The spin 1 bilinear-biquadratic model on square lattice in the region $0<ϕ<π/4$ is studied in a fermion representation with a p-wave pairing BCS type mean-field theory. Our results show there may exist a non-trivial gapped spin liquid with time-reversal symmetry spontaneously breaking. This exotic state manifests its topological nature by forming chiral states at the edges. To show it more clear, we set up and solved a ribbon system. We got a gapless dispersion representing the edge modes beneath the bulk modes. The edge modes with nonzero longitudinal momentum ($k_{x}\neq0$) convect in opposite directions at the two edges, which leads to a two-fold degeneracy. While the zero longitudinal momentum ($k_{x}=0$) modes turn out to be Majorana fermion states. The edge spin correlation functions are found to decay in a power law with the distance increasing. We also calculated the contribution of the edge modes to the specific heat and obtained a linear law at low temperatures.

cond-mat.str-el↗

arXiv2012

Preparation of NOON State Induced by Macroscopic Quantum Tunneling in an Ising Chain

In this brief report, we propose a possible way, theoretically and experimentally, to generate a NOON state of the two degenerate ferromagnetic ground states of the Transverse Ising Model. In our scheme we employ the macroscopic quantum tunneling (MQT) effect between the two degenerate ferromagnetic ground states to realize the NOON state. Our calculation about the MQT process is based on a higher-order degenerate perturbation method. After doing a transformation, the MQT process could also be treated as the hopping of individual virtual fermions in the spin chain, which will leads to an analytical description of tunneling process. The experimental feasibility for generating the NOON state is discussed in the setup of linear ion trap.

quant-ph↗

arXiv2012

Emergent Supersymmetric Many-Body Systems in Doped Z2 Topological Spin Liquid of the Toric-Code Model

In this paper, we studied the doped Z2 topological spin liquid of the toric-code model. We found that the doped holes become supersymmetric particles. The ground state of the doped Z2 topological spin liquid becomes new matters of quantum states - supersymmetric Bose-Einstein condensation or supersymmetric superfluid. As a result, this system provides a unique example of manipulatable supersymmetric many-body system.

cond-mat.str-el↗

arXiv2012

Particle-Hole Symmetry Protected Zero Modes on Vacancies in the Topological Insulators and Topological Superconductors on the Honeycomb Lattice

In this paper we study the quantum properties of the lattice vacancy in topological band insulators (TBIs) and topological superconductors (TSCs) on honeycomb lattice with particle-hole symmetry. Each vacancy has one zero mode for the Haldane model and two zero modes for the Kane-Mele model. In addition, in TSCs on honeycomb lattice with particle-hole symmetry, we found the existence of the Majorana zero modes around the vacancies. These zero energy modes are protected by particle-hole symmetry of these topological sates.

cond-mat.mes-hall↗

arXiv2012

Majorana Edge States for Z2 Topological Orders of the Wen-plaquette Model and the Toric-code Model

In this paper we study the symmetry protected Majorana edge states for the Z2 topological order of the Wen-plaquette model and the toric-code model and calculate the dispersion of the Majorana edge states. For the system with translational symmetry, the Majorana edge states are gapless and have the nodal points at k=0 and k=pi. For the edge states of the toric-code model without translational symmetry, the edge modes become gapped.

cond-mat.str-el↗

arXiv2012

Topological superfluid in a fermionic bilayer optical lattice

In this paper, a topological superfluid phase with Chern number C=1 possessing gapless edge states and non-Abelian anyons is designed in a C=1 topological insulator proximity to an s-wave superfluid on an optical lattice with the effective gauge field and layer-dependent Zeeman field coupled to ultracold fermionic atoms pseudo spin. We also study its topological properties and calculate the phase stiffness by using the random-phase-approximation approach. Finally we derive the temperature of the Kosterlitz-Thouless transition by means of renormalized group theory. Owning to the existence of non-Abelian anyons, this C=1 topological superfluid may be a possible candidate for topological quantum computation.

cond-mat.supr-con↗

arXiv2012

Mott Insulator-Superfluid Transition in a Generalized Bose-Hubbard Model with Topologically Non-trivial Flat-Band

In this paper, we studied a generalized Bose-Hubbard model on a checkerboard lattice with topologically nontrivial flat-band. We used mean-field method to decouple the model Hamiltonian and obtained phase diagram by Landau theory of second-order phase transition. We further calculate the energy gap and the dispersion of quasi-particle or quasi-hole in Mott insulator state and found that in strong interaction limit the quasi-particles or the quasi-holes also have flat bands.

cond-mat.quant-gas↗

arXiv2012

Ferromagnetism and Antiferromagnetism of Correlated Topological Insulator with Flat Band

In this paper, based on the mean field approach and random-phase-approximation, we study the magnetic properties of the spinful Haldane model on honeycomb lattice of topological flat band with on-site repulsive Coulomb interaction. We find that the antiferromagnetic (AF) order is more stable than ferromagnetic (FM) order at (or near) half-filling; while away from half-filling the phase diagram becomes complex: At large doping, FM order is more stable than AF order due to the flatness of band structure. In particular, we find that at quarter filling case, the system becomes a Q=1$ topological insulator which is induced by the FM order.

cond-mat.str-el↗

arXiv2012

Composite Spin Liquid in Correlated Topological Insulator - Spin Liquid without Spin-Charge Separation

In this paper, we found a new type of insulator - composite spin liquid which can be regarded as a short range B-type topological spin-density-wave. Composite spin liquid is topological ordered state beyond the classification of traditional spin liquid states. The elementary excitations are the "composite electrons" with both spin degree of freedom and charge degree of freedom, together with topological spin texture. This topological state supports chiral edge mode but no topological degeneracy.

cond-mat.str-el↗

arXiv2012

Quantum simulation of artificial Abelian gauge field using nitrogen-vacancy center ensembles coupled to superconducting resonators

We propose a potentially practical scheme to simulate artificial Abelian gauge field for polaritons using a hybrid quantum system consisting of nitrogen-vacancy center ensembles (NVEs) and superconducting transmission line resonators (TLR). In our case, the collective excitations of NVEs play the role of bosonic particles, and our multiport device tends to circulate polaritons in a behavior like a charged particle in an external magnetic field. We discuss the possibility of identifying signatures of the Hofstadter "butterfly" in the optical spectra of the resonators, and analyze the ground state crossover for different gauge fields. Our work opens new perspectives in quantum simulation of condensed matter and many-body physics using hybrid spin-ensemble circuit quantum electrodynamics system. The experimental feasibility and challenge are justified using currently available technology.

quant-ph↗