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Su-Peng Kou

Publications and source records attributed to Su-Peng Kou.

At least 55 records · Page 3Linked to original sources
arXiv2018

Emergent Quantum Dynamics of Vortex Line under Linear Local Induction Approximation

Using the linear local induction approximation, we investigated the self-induced motion of a vortex line that corresponds to the motion of a particle in quantum mechanics. Concerning Kelvin waves, the effective Schrödinger equation, physical quantities operators, and the corresponding path-integral formula are obtained. The vortex line-particle mapping may help in understanding particle motion in quantum mechanics.

quant-ph↗
arXiv2017

Fermi Arcs in Tilted Weyl Semimetals: Classification, Evolution and Transport Properties

The Weyl semimetal is a new quantum state of topological semimetal, of which topological surface states -- the Fermi arcs exist. In this paper, the Fermi arcs in Weyl semimetals are classified into two classes -- class-1 and class-2. Based on a tight-binding model, the evolution and transport properties of class-1/2 Fermi arcs are studied via the tilting strength of the bulk Weyl cones. The (residual) anomalous Hall conductivity of topological surface states is a physical consequence of class-1 Fermi arc and thus class-1 Fermi arc becomes a nontrivial topological property for hybrid or type-II Weyl semimetal. Therefore, this work provides an intuitive method to learn topological properties of Weyl semimetal.

cond-mat.mtrl-sci↗
arXiv2017

Duality of deconfined quantum critical point in two dimensional Dirac semimetals

In this paper we discuss the N$\acute{e}$el and Kekul$\acute{e}$ valence bond solids quantum criticality in graphene Dirac semimetal. Considering the quartic four-fermion interaction $g(\barψ_iΓ_{ij}ψ_j)^2$ that contains spin,valley, and sublattice degrees of freedom in the continuum field theory, we find the microscopic symmetry is spontaneously broken when the coupling $g$ is greater than a critical value $g_c$. The symmetry breaking gaps out the fermion and leads to semimetal-insulator transition. All possible quartic fermion-bilinear interactions give rise to the uniform critical coupling, which exhibits the multicritical point for various orders and the Landau-forbidden quantum critical point. We also investigate the typical critical point between N$\acute{e}$el and Kekul$\acute{e}$ valence bond solid transition when the symmetry is broken. The quantum criticality is captured by the Wess-Zumino-Witten term and there exist a mutual-duality for N$\acute{e}$el-Kekul$\acute{e}$ VBS order. We show the emergent spinon in the N$\acute{e}$el-Kekul$\acute{e}$ VBS transition , from which we conclude the phase transition is a deconfined quantum critical point. Additionally, the connection between the index theorem and zero energy mode bounded by the topological defect in the Kekul$\acute{e}$ VBS phase is studied to reveal the N$\acute{e}$el-Kekul$\acute{e}$ VBS duality.

cond-mat.str-el↗
arXiv2017

Type II Nodal line Semimetal

Recently, topological semimetals become hot topic in condensed matter physics, including Dirac semimetal, Weyl semimetal, and nodal line semimetal (NLSM). In this paper, a new type of node- line semimetal - type-II NLSM is proposed based on a two-band cubic lattice model. For type-II NLSM, the zero energy bulk states have a closed loop in momentum space but the (local) Weyl cones on nodal line become tilted. The effect of magnetic field and that of correlation on type-II NLSM are studied. In particular, after considering repulsive interaction and additional spin degrees of freedom, different types of long range magnetic orders appear in bulk states. In addition, the interaction-induced ferromagnetic order of surface states may exist. At critical point between type-I NLSM and type-II NLSM, arbitrary tiny interaction induces ferromagnetic order due to a flat band at Fermi surface.

cond-mat.str-el↗
arXiv2017

Knot Physics on Entangled Vortex-Membranes: Classification, Dynamics and Effective Theory

In this paper, knot physics on entangled vortex-membranes are studied including classification, knot dynamics and effective theory. The physics objects in this paper are entangled vortex-membranes that are called composite knot-crystals. Under projection, a composite knot-crystal is reduced into coupled zero-lattices. In the continuum limit, the effective theories of coupled zero-lattices become quantum field theories. After considering the topological interplay between knots and different types of zero-lattices, gauge interactions emerge. Based on a particular composite knot-crystal with (N=4, M=3) (we call it standard knot-crystal), the derived effective model becomes the (one-flavor) Standard model. As a result, the knot physics may provide an alternative interpretation on quantum field theory.

physics.gen-ph↗
arXiv2017

Kelvin Waves and Dynamic Knots on Vortex-Membrane

Quantum mechanics is a successful theory that describes the behavior of photons, electrons, and other atomic- and molecular-scale objects. However, it is far from being well understood. In this paper, a new theory - knot physics for entangled vortex-membranes is developed to explore the underline physics of quantum mechanics. From point view of information, three dimensional quantum Dirac model is developed to effectively describe the fluctuations of local deformation of vortex-membranes: The elementary excitations are knots with information unit; The physics quality to describe local deformation is knot density that is defined by the density of zeros between two projected vortex-membranes; The Biot-Savart equation for Kelvin waves becomes Schrodinger equation for probability waves of knots; the classical functions for perturbative Kelvin waves become wave functions for knots; The probability of quantum mechanics comes from dynamic projection for inner observers owing to "fast clock" effect; The angular frequency for leapfrogging motion plays the role of the mass of knots; etc. This work would help people to understand the mystery of quantum mechanics.

physics.gen-ph↗
arXiv2017

Topological Interplay between Knots and Entangled Vortex-Membranes

In this paper, the Kelvin wave and knot dynamics are studied on three dimensional smoothly deformed entangled vortex-membranes in five dimensional space. Owing to the existence of local Lorentz invariance and diffeomorphism invariance, in continuum limit gravity becomes an emergent phenomenon on 3+1 dimensional zero-lattice (a lattice of projected zeroes): On the one hand, the deformed zero-lattice can be denoted by curved space-time for knots; on the other hand, the knots as topological defect of 3+1 dimensional zero-lattice indicates matter may curve space-time. This work would help researchers to understand the mystery in gravity.

physics.gen-ph↗
arXiv2017

Weyl Bogoliubov excitations in Bose-Hubbard extension of Weyl semimetal

In this paper, a Bose-Hubbard extension of a Weyl semimetal is proposed that can be realized for ultracold atoms using laser assisted tunneling and Feshbach resonance technique in three dimensional optical lattices. The global phase diagram is obtained consisting of a superfluid phase and various Mott insulator phases by using Landau theory. The Bogoliubov excitation modes for the weakly interacting case have nontrivial properties (Weyl nodes, bosonic surface arc, etc.) analogs of those in Weyl semimetals of electronic systems, which are smoothly carried over to that of Bloch bands for the noninteracting case. The properties of the insulating phases for the strongly interacting case are explored by calculating both the quasiparticle and quasihole dispersion relation, which shows two quasiparticle spectra touch at Weyl nodes.

cond-mat.quant-gas↗
arXiv2016

Tunable Weyl Semi-metal and its Possible Realization in Optical Lattice

Weyl semimetal (WSM) is an exotic topological state in condensed matter physics. In this paper, based on a two-band cubic lattice model, we studied WSMs with a pair of tunable Weyl nodes. It is pointed out that there exist three types of WSMs with different tilt strengths: type-I WSM, type-II WSM and type-1.5 WSM. In particular, type-1.5 WSM has one type-I node and one type-II node. We studied chiral modes, surface Fermi arcs and quantum anomalous Hall effect in different types of WSMs. In addition, we give an experimental setup to realize the different types of WSMs based on timely technique.

cond-mat.str-el↗
arXiv2016

Electronic transport of bilayer graphene with asymmetry line defects

In this paper, we study the quantum properties of a bilayer graphene with (asymmetry) line defects. The localized states are found around the line defects. Thus, the line defects on one certain layer of the bilayer graphene can lead to an electric transport channel. By adding a bias potential along the direction of the line defects, we calculate the electric conductivity of bilayer graphene with line defects using Landauer-Büttiker theory, and show that the channel affects the electric conductivity remarkably by comparing the results with those in a perfect bilayer graphene. This one-dimensional line electric channel has the potential to be applied in the nanotechnology engineering.

cond-mat.mes-hall↗
arXiv2016

The Simulation of Non-Abelian Statistics of Majorana Fermions in Ising Chain with Z2 Symmetry

In this paper, we numerically study the non-Abelian statistics of the zero-energy Majorana fermions on the end of Majorana chain and show its application to quantum computing by mapping it to a spin model with special symmetry. In particular, by using transverse-field Ising model with Z2 symmetry, we verify the nontrivial non-Abelian statistics of Majorana fermions. Numerical evidence and comparison in both Majorana-representation and spin-representation are presented. The degenerate ground states of a symmetry protected spin chain therefore previde a promising platform for topological quantum computation.

cond-mat.mes-hall↗
arXiv2016

Topological end states in two-orbital double-exchange model for colossal magnetoresistive manganites

Manganites are famous mostly for the colossal magnetoresistive effect, which involves the phase separation between ferromagnetic phase and charge-ordered CE-type antiferromagnetic phases. Furthermore, manganites contain some typical magnetic ferroelectrics, e.g. E-type antiferromagnetic $o$-HoMnO$_3$. Here we re-examined these zigzag-winding antiferromagnetic phases (CE-type and E-type antiferromagnets) from the topological perspective. Our theoretical analysis proved that the E-type phase is a weak topological insulator belonging to the $\mathbb{Z}$ class. In momentum space, we classify the symmetries of this phase, and find the three symmetry operators for the chiral, particle-hole, and time-reversal symmetry. The CE-type phase can be described by the Duffin-Kemmer-Petiau algebra, implying that it is a new class of topological insulator and hence extends the existing classification. The corresponding topological end states are demonstrated via numerical calculations, which may implicate the experimental observed ferromagnetic edge states in manganite strips (Nat. Commun. 6, 6179 (2015)) and may play a crucial role in the colossal magnetoresistive effect.

cond-mat.mtrl-sci↗
arXiv2015

Topological Hierarchy Insulators and Topological Fractal Insulators

Topological insulators are new states of quantum matter with metallic edge/surface states. In this paper, we pointed out that there exists a new type of particle-hole symmetry-protected topological insulator - topological hierarchy insulator (THI), a composite topological state of a (parent) topological insulator and its defect-induced topological mid-gap states. A particular type of THI is topological fractal insulator, that is a THI with self-similar topological structure. In the end, we discuss the possible experimental realizations of THIs.

cond-mat.str-el↗
arXiv2015

Verifying Non-Abelian Statistics by Numerical Braiding Majorana Fermions

Recently, Majorana fermions (MFs) have attracted intensive attention because of their possible non-Abelian statistics. This paper points out an approach to verify the non-Abelian statistics of MFs in topological superconductors. We introduce a single particle representation of braiding operators that obey anti-commutating relation of Bogolubov-de Gennes (BdG) states. From the relationship between the braiding operator of MFs and that of BdG states, we verify non-Abelian statistics of MFs in 1D and 2D topological SCs.

cond-mat.str-el↗
arXiv2015

Classification of Majorana Fermions in Two-Dimensional Topological Superconductors

Recently, Majorana Fermions (MFs) have attracted intensive attention due to their exotic statistics and possible applications in topological quantum computation (TQC). They are proposed to exist in various two-dimensional (2D) topological systems, such as px+ipy topological superconductor and nanowire-superconducting hybridization system. In this paper, two types of Majorana Fermions with different polygon sign rules are pointed out. A "smoking gun" numerical evidence to identify MF's classification is presented through looking for the signature of a first order topological quantum phase transition. By using it, several 2D topological superconductors are studied.

cond-mat.mes-hall↗
arXiv2014

Ultracold Quantum Gases in Optical Lattice with Topological Defects: Its Physics and Experimental Proposal

In this paper we give a proposal to realize optical lattices with manipulated dislocations and study the physics of ultracold quantum gas on a two-dimensional (2D) optical square lattice with dislocations. In particular, the dislocations may induce fractional topological flux on 2D Peierls optical lattice. These results pave new approach to study the quantum many-body systems on an optical lattice with controllable topological lattice-defects, including the dislocations, topological fluxes.

cond-mat.quant-gas↗
arXiv2014

Theory of Vacancy-Induced Intrinsic Magnetic Impurity with Quasi-Localized Spin Moment in Graphene

In this paper, by considering the Hubbard model on a honeycomb lattice, we developed a theory for the intrinsic magnetic impurities (MIs) with the quasi-localized spin moments induced by the vacancies in graphene. Because the intrinsic MIs are characterized by the zero modes that are rthotropic to the itinerant electrons, their properties are much different from those of Anderson MIs with the well-localized spin moments.

cond-mat.mes-hall↗