arXiv subjects

Yupeng Wang

Publications and source records attributed to Yupeng Wang.

At least 109 records · Page 6Linked to original sources

arXiv2011

Thermodynamics and spin-charge separation of one-dimensional strongly repulsive three-component fermions

The low temperature thermodynamics of one-dimensional strongly repulsive SU(3) fermions in the presence of a magnetic field is investigated via the Yang-Yang thermodynamic Bethe ansatz method. The analytical free energy and magnetic properties of the model at low temperatures in a weak magnetic field are derived via the Wiener-Hopf method. It is shown that the low energy physics can be described by spin-charge separated conformal field theories of an effective Tomonaga-Luttinger liquid and an antiferromagnetic SU(3) Heisenberg spin chain. Beyond the Tomonaga-Luttinger liquid regime, the equation of state is given in terms of the polylog function for a weak external field. The results obtained are essential for further study of quantum criticality in strongly repulsive three-component fermions.

cond-mat.quant-gas↗

arXiv2011

An unified minimum effective model of magnetism in iron-based superconductors

Since 2008, many new families of iron-based high temperature (high-$T_c$) superconductors have been discovered \cite{Hosono,ChenXH,FeTe,ChenXL}. Unlike all parent compounds of cuprates that share a common antiferromagnetically (AF) ordered ground state, those of iron-based superconductors exhibit many different AF ordered ground states, including collinear-AF (CAF) state in ferropnictides \cite{caf}, bicollinear-AF (BCAF) state in 11-ferrochalcogenide $FeTe$ \cite{bcaf,bcaf2}, and block-AF (BAF) state in 122-ferrochalcogenide $K_{0.8}Fe_{1.6}Se_2$ \cite{baf}. While the universal presence of antiferromagnetism suggests that superconductivity is strongly interrelated with magnetism, the diversity of the AF ordered states obscures their interplay. Here we show that all magnetic phases can be unified within an effective magnetic model. This model captures three incommensurate magnetic phases, two of which have been observed experimentally. The model characterizes the nature of phase transitions between the different magnetic phases and explains a variety of magnetic properties, such as spin-wave spectra and electronic nematism. Most importantly, by unifying the understanding of magnetism, we cast new insight on the key ingredients of magnetic interactions which are critical to the occurrence of superconductivity.

cond-mat.supr-con↗

arXiv2011

Stable Fulde-Ferrell-Larkin-Ovchinnikov pairing states in 2D and 3D optical lattices

We present the study of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing states in the $p$-orbital bands in both two and three-dimensional optical lattices. Due to the quasi one-dimensional band structure which arises from the unidirectional hopping of the orthogonal $p$-orbitals, the pairing phase space is not affected by spin imbalance. Furthermore, interactions build up high dimensional phase coherence which stabilizes the FFLO states in 2D and 3D optical lattices in a large parameter regime in phase diagram. These FFLO phases are stable with imposing the inhomogeneous trapping potential. Their entropies are comparable to those of the normal states at finite temperatures.

cond-mat.quant-gas↗

arXiv2011

Quantum Spinon Oscillations

The full quantum dynamics of a spinon under external magnetic fields is investigated by using the time-evolving block decimation (TEBD) method within the microcanonical picture of transport. We show that the center of the spinon oscillates back and forth in the absence of dissipation. The quantum many-body behavior can be understood in a single-particle picture of transport and Bloch oscillations, where quantum fluctuations induce finite life times. Transport, oscillations and lifetimes can be tuned to some degree separately by external fields. Other nontrivial dynamics such as resonance as well as chaos have also been discussed.

cond-mat.str-el↗

arXiv2011

D-wave bosonic pair in an optical lattice

We present a bosonic model, in which two bosons may form a bound pair with d-wave symmetry via the four-site ring exchange interaction. A d-wave pairing superfluid as well as a d-wave density wave (DDW) state, are proposed to be achievable in this system. This exotic bosonic system can be realized in the BEC zone of a two-dimensional attractive p-band spinless fermionic system. By the mean field approach, we find that at low densities, the d-wave pairs may condensate, leading to a d-wave bosonic paired superfluid. At some particular filling factors, a novel phase, d-wave density wave state, emerges. We study this DDW state and its corresponding quantum phase transition in a two-leg ladder by the time-evolving block decimation (TEBD) method.

cond-mat.quant-gas↗

arXiv2011

Quantum magnetism of ultra-cold fermion systems with the symplectic symmetry

We numerically study quantum magnetism of ultra-cold alkali and alkaline-earth fermion systems with large hyperfine spin $F=3/2$, which are characterized by a generic $Sp(N)$ symmetry with N=4. The methods of exact diagonalization (ED) and density-matrix-renormalization-group are employed for the large size one-dimensional (1D) systems, and ED is applied to a two-dimensional (2D) square lattice on small sizes. We focus on the magnetic exchange models in the Mott-insulating state at quarter-filling. Both 1D and 2D systems exhibit rich phase diagrams depending on the ratio between the spin exchanges $J_0$ and $J_2$ in the bond spin singlet and quintet channels, respectively. In 1D, the ground states exhibit a long-range-ordered dimerization with a finite spin gap at $J_0/J_2>1$, and a gapless spin liquid state at $J_0/J_2 \le 1$, respectively. In the former and latter cases, the correlation functions exhibit the two-site and four-site periodicities, respectively. In 2D, various spin correlation functions are calculated up to the size of $4\times 4$. The Neel-type spin correlation dominates at large values of $J_0/J_2$, while a $2\times 2$ plaquette correlation is prominent at small values of this ratio. Between them, a columnar spin-Peierls dimerization correlation peaks. We infer the competitions among the plaquette ordering, the dimer ordering, and the Neel ordering in the 2D system.

cond-mat.quant-gas↗

arXiv2011

dMotifGreedy: a novel tool for de novo discovery of DNA motifs with enhanced power of reporting distinct motifs

De novo discovery of over-represented DNA motifs is one of the major challenges in computational biology. Although numerous tools have been available for de novo motif discovery, many of these tools are subject to local optima phenomena, which may hinder detection of multiple distinct motifs. A greedy algorithm based tool named dMotifGreedy was developed. dMotifGreedy begins by searching for candidate motifs from pair-wise local alignments of input sequences and then computes an optimal global solution for each candidate motif through a greedy algorithm. dMotifGreedy has competitive performance in detecting a true motif and greatly enhanced performance in detecting multiple distinct true motifs. dMotifGreedy is freely available via a stand-alone program at http://lambchop.ads.uga.edu/dmotifgreedy/download.php.

q-bio.GN↗

arXiv2011

Spontaneous trimerization in two-dimensional Antiferromagnets

In this paper, we propose a novel quantum paramagnetic state in two-dimensional antiferromagnets: the spontaneously trimer state, which is constructed by the trimers of spins. Each trimer is a singlet state formed by three neighboring spins with SU(3) symmetry. A frustrated spin-1 Heisenberg model in the kagome lattice is investigated. By analogy to the pseudo-potential approach in the fractional quantum Hall effect (FQHE), we find that the trimer state provides a perfect description for the exact ground state of this model. Other interesting properties, such as the local excitations as well as magnetization plateaus have also been investigated. It is shown that this novel state would deepen our understanding of the nature of the many-body entanglement in the two-dimensional strong correlated systems.

cond-mat.str-el↗

arXiv2010

Analytical thermodynamics of a strongly attractive three-component Fermi gas in one dimension

Ultracold three-component atomic Fermi gases in one dimension are expected to exhibit rich physics due to the presence of trions and different pairing states. Quantum phase transitions from the trion state into a paired phase and a normal Fermi liquid occur at zero temperature. We derive the analytical thermodynamics of strongly attractive three-component one-dimensional fermions with SU(3) symmetry via the thermodynamic Bethe ansatz method in unequal Zeeman splitting fields $H_1$ and $H_2$. We find explicitly that for low temperature the system acts like either a two-component or a three-component Tomonaga-Luttinger liquid dependent on the system parameters. The phase diagrams for the chemical potential and specific heat are presented for illustrative values of the Zeeman splitting. We also demonstrate that crossover between different Tomonaga-Luttinger liquid phases evolve singular behaviour in specific heat and entropy as the temperature tends to zero. Beyond Tomonaga-Luttinger liquid physics, we obtain the equation of state which provides a precise description of universal thermodynamics and quantum criticality in three-component strongly attractive Fermi gases.

cond-mat.quant-gas↗

arXiv2010

Quantum criticality in disordered bosonic optical lattices

Using the exact Bose-Fermi mapping, we study universal properties of ground-state density distributions and finite-temperature quantum critical behavior of one-dimensional hard-core bosons in trapped incommensurate optical lattices. Through the analysis of universal scaling relations in the quantum critical regime, we demonstrate that the superfluid to Bose glass transition and the general phase diagram of disordered hard-core bosons can be uniquely determined from finite-temperature density distributions of the trapped disordered system.

cond-mat.quant-gas↗

arXiv2010

Chiral topological excitonic insulator in semiconductor quantum wells

We present a scheme to realize the chiral topological excitonic insulator in semiconductor heterostructures which can be experimentally fabricated with a coupled quantum well adjacent to twoferromagnetic insulating films. The different mean-field chiral topological orders, which are due to the change in the directions of the magnetization of the ferromagnetic films, can be characterized by the TKNN numbers in the bulk system as well as by the winding numbers of the gapless states in the edged system. Furthermore, we propose an experimental scheme to detect the emergence of the chiral gapless edge state and distinguish different chiral topological orders by measuring the thermal conductance.

cond-mat.mes-hall↗

arXiv2010

Hidden Sp(2s+1)- or SO(2s+1)-symmetry and new exactly solvable models in ultracold atomic systems

The high spin ultracold atom models with a special form of contact interactions, i.e., the scattering lengthes in the total spin-$2,4 \cdots$ channels are equal but may be different from that in the spin-0 channel, is studied. It is found that those models have either $Sp(2s+1)$-symmetry for the fermions or $SO(2s+1)$-symmetry for the bosons in the spin sector. Based on the symmetry analysis, a new class of exactly solvable models is proposed and solved via the Bethe ansatz. The ground states for repulsive fermions are also discussed.

cond-mat.str-el↗

arXiv2010

Impurity effects and ferromagnetism in excitonic insulators

Both nonmagnetic and magnetic impurity effects in spin singlet and triplet excitonic insulators were investigated. The bound state energies caused by single impurity were given. The different compositions of the bound states can be used to detect the symmetry of the excitonic insulators. In finite concentration problems, nonmagnetic impurities showed same pair-breaking effect in singlet and triplet excitonic insulators while magnetic impurities showed weaker pair-breaking effect in triplet excitonic insulators than in singlet ones. The pair-breaking effects suppressed the ferromagnetic range via doping and gave a natural explaination for experimental results.

cond-mat.dis-nn↗

arXiv2010

Exciton condensation and fractional charge in a bilayer two-dimension electron gas adjacent to a superconductor film

We study the exciton condensate (EC) in a bilayer two-dimension-electron-gas (2DEG) adjacent to a type-II superconductor thin film with an array of pinned vortex lattices. By applying continuum low energy theory and carrying numerical simulations of lattice model within mean-field approximation, we find that if the order parameter of EC has a vortex profile, there are exact zero modes and associated \emph{rational} fractional charge for zero pseudospin potential ($μ$) and average chemical potential ($h$): $μ$=0 and $h$=0; while for $μ\mathtt{\neq}0$ and $h$=0, intervalley mixing splits the zero energy levels, and the system exhibits \emph{irrational} fractional \emph{axial} charge.

cond-mat.mes-hall↗

arXiv2010

Resonance Scattering in Optical Lattices and Molecules: Interband versus Intraband Effects

We study the low-energy two-body scattering in optical lattices with all higher-band effects included in an effective potential, using a renormalization group approach. As the potential depth reaches a certain value, a resonance of low energy scattering occurs even when the negative s-wave scattering length $(a_s)$ is much shorter than the lattice constant. These resonances can be mainly driven either by interband or intraband effects or by both, depending on the magnitude of $a_s$. Furthermore the low-energy scattering matrix in optical lattices has a much stronger energy-dependence than that in free space. We also investigate the momentum distribution for molecules when released from optical lattices.

cond-mat.quant-gas↗

arXiv2010

Ground-state and dynamic properties of hard-core bosons in one-dimensional incommensurate optical lattices with harmonic trap

We study properties of the strongly repulsive Bose gas on one-dimensional incommensurate optical lattices with a harmonic trap, which can be deal with by using the exact numerical method through the Bose-Fermi mapping. We first exploit the phase transition of the hard-core bosons in the optical lattices from superfluid-to-Bose-glass phase as the strength of the incommensurate potential increases. Then we study the dynamical properties of the system after suddenly switching off the harmonic trap. We calculate the one-particle density matrices, momentum distributions, the natural orbitals and their occupations for both the static and dynamic systems. Our results indicate that the Bose-glass phase and superfluid phase display quite different properties and expansion dynamics.

cond-mat.dis-nn↗

arXiv2010

Polarized Fermi gases in asymmetric optical lattices

The zero-temperature phase diagrams of imbalanced two-species Fermi gases are investigated in asymmetric optical lattices with arbitrary potential depths, based on the exact spectrum instead of the Fermi-Hubbard model. We study the effect of lattice potentials and atomic densities to the fully paired Bardeen-Cooper-Schrieffer (BCS) state and particularly the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. It is found that the increasing lattice potential favors BCS at low densities because of the enhanced effective coupling; whereas FFLO is favored at intermediate densities when the system undergoes a dimensional crossover. Finally using local density approximation we study the evolution of phase profile in the presence of external harmonic traps by merely tuning the lattice potentials.

cond-mat.quant-gas↗

arXiv2009

Superfluid to Bose-glass transition of hard core bosons in one-dimensional incommensurate optical lattice

We study superfluid to Anderson insulator transition of strongly repulsive Bose gas in a one dimensional incommensurate optical lattice. In the hard core limit, the Bose-Fermi mapping allows us to deal with the system exactly by using the exact numerical method. Based on the Aubry-André model, we exploit the phase transition of the hard core boson system from superfluid phase with all the single particle states being extended to the Bose glass phase with all the single particle states being Anderson localized as the strength of the incommensurate potential increasing relative to the amplitude of hopping. We evaluate the superfluid fraction, the one particle density matrices, momentum distributions, the natural orbitals and their occupations. All of these quantities show that there exists a phase transition from superfluid to insulator in the system.

cond-mat.quant-gas↗