arXiv subjects

Z. Y. Zhang

Publications and source records attributed to Z. Y. Zhang.

At least 55 records · Page 3Linked to original sources

arXiv2015

Is $d^*$ a candidate of hexaquark-dominated exotic state?

We confirm our previous prediction of a $d^*$ state with $I(J^P)=0(3^+)$ [Phys. Rev. C 60, 045203 (1999)] and report for the first time based on a microscopic calculation that $d^*$ is a hexaquark dominated exotic state as it has about 2/3 hidden color (CC) configurations. By performing a more elaborate dynamical coupled-channels investigation of the $ΔΔ$-CC system within the framework of resonating group method (RGM) in a chiral quark model, we found that the $d^*$ state has a mass of about 2.38-2.42 GeV, a root-mean-square radius (RMS) of 0.76-0.88 fm, and a CC fraction of 66%-68%. The last ensures that the $d^*$ has a rather narrow width which, together with the quantum numbers and our calculated mass, is consistent with the newly observed resonance-like structure ($M\approx 2380$ MeV, $Γ\approx 70$ MeV) in double-pionic fusion reactions reported by WASA-at-COSY Collaboration.

nucl-th↗

arXiv2015

Orientation and strain modulated electronic structures in puckered arsenene nanoribbons

Orthorhombic arsenene was recently predicted as an indirect bandgap semiconductor. Here, we demonstrate that nanostructuring arsenene into nanoribbons can successfully transform the bandgap to be direct. It is found that direct bandgaps hold for narrow armchair but wide zigzag nanoribbons, which is dominated by the competition between the in-plane and out-of-plane bondings. Moreover, straining the nanoribbons also induces a direct bandgap and simultaneously modulates effectively the transport property. The gap energy is largely enhanced by applying tensile strains to the armchair structures. In the zigzag ones, a tensile strain makes the effective mass of holes much higher while a compressive strain cause it much lower than that of electrons. Our results are crutial to understand and engineer the electronic properties of two dimensional materials beyond the planar ones like graphene.

cond-mat.mes-hall↗

arXiv2015

Negative Poisson's ratios in few-layer orthorhombic arsenic from first-principles calculations

A material exhibiting a negative Poisson's ratio is always one of the leading topics in materials science, which is due to the potential applications in those special areas such as defence and medicine. In this letter, we demonstrate a new material, few-layer orthorhombic arsenic, also possesses the negative Poisson's ratio. For monolayer arsenic, the negative Poisson's ratio is predicted to be around -0.09, originated from the hinge-like structure within the single layer of arsenic. When the layer increases, the negative Poisson's ratio becomes more negative and finally approaches the limit at four-layer, which is very close to the bulk's value of -0.12. The underlying mechanism is proposed for this layer-dependent negative Poisson's ratio, where the internal bond lengths as well as the normal Poisson's ratio within layer play a key role. The study like ours sheds new light on the physics of negative Poisson's ratio in those hinge-like nano-materials.

cond-mat.mtrl-sci↗

arXiv2014

A theoretical study of blue phosphorene nanoribbons based on first-principles calculations

Based on first-principles calculations, we present a quantum confinement mechanism for the band gaps of blue phosphorene nanoribbons (BPNRs) as a function of their widths. The BPNRs considered have either armchair or zigzag shaped edges on both sides with hydrogen saturation. Both the two types of nanoribbons are shown to be indirect semiconductors. An enhanced energy gap of around 1 eV can be realized when the width decreases to about 10 ang. The underlying physics is ascribed to the quantum confinement. More importantly, the quantum confinement parameters are obtained by fitting the calculated gaps with respect to their widths. The results show that the quantum confinement in armchair nanoribbons is stronger than that in zigzag ones. This study provides an efficient approach to tune the energy gap in BPNRs.

cond-mat.mtrl-sci↗

arXiv2013

Sigma_c Dbar and Lambda_c Dbar states in a chiral quark model

The S-wave Sigma_c Dbar and Lambda_c Dbar states with isospin I=1/2 and spin S=1/2 are dynamically investigated within the framework of a chiral constituent quark model by solving a resonating group method (RGM) equation. The results show that the interaction between Sigma_c and Dbar is attractive, which consequently results in a Sigma_c Dbar bound state with the binding energy of about 5-42 MeV, unlike the case of Lambda_c Dbar state, which has a repulsive interaction and thus is unbound. The channel coupling effect of Sigma_c Dbar and Lambda_c Dbar is found to be negligible due to the fact that the gap between the Sigma_c Dbar and Lambda_c Dbar thresholds is relatively large and the Sigma_c Dbar and Lambda_c Dbar transition interaction is weak.

nucl-th↗

arXiv2012

Possible $D\bar{D}$ and $B\bar{B}$ Molecular states in a chiral quark model

We perform a systematic study of the bound state problem of $D\bar{D}$ and $B\bar{B}$ systems by using effective interaction in our chiral quark model. Our results show that both the interactions of $D\bar{D}$ and $B\bar{B}$ states are attractive, which consequently result in $I^G(J^{PC})=0^+(0^{++})$ $D\bar{D}$ and $B\bar{B}$ bound states.

nucl-th↗

arXiv2012

$Z_b(10650)$ and $Z_b(10610)$ states in a chiral quark model

We perform a systematic study of $B\bar{B}^*$, $B^*\bar{B}^*$, $D\bar{D}^*$ and $D^*\bar{D}^*$ systems by using effective interaction in our chiral quark model. Our results show that the interactions of $B\bar{B}^*$, $B^*\bar{B}^*$, $D\bar{D}^*$ and $D^*\bar{D}^*$ states are attractive, which consequently result in $B\bar{B}^*$, $B^*\bar{B}^*$, $D\bar{D}^*$ and $D^*\bar{D}^*$ bound states. The recent observed exotic-like hadrons of $Z_b(10610)$ and $Z_b(10650)$ are, therefore in our approach, interpreted as loosely bound states of $B\bar{B}^*$ and $B^*\bar{B}^*$, while X(3872) and Y(3940) are $D\bar{D}^*$ and $D^*\bar{D}^*$ molecule states, respectively.

hep-ph↗

arXiv2011

Dynamical coupled-channel study of K* K*bar and omega phi states in a chiral quark model

A dynamical coupled-channel study of K* K*bar state with isospin 0 and omega phi state is performed within both the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the energies of the octet and decuplet baryon ground states, the binding energy of the deuteron, the nucleon-nucleon (NN) scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The results show that the interactions of K* K*bar states are attractive, which consequently result in K* K*bar bound states with the binding energies of about 10-70 MeV, and contrarily, no omega phi bound state is obtained. The channel coupling effect of K* K*bar and omega phi is found to be considerably large, which makes the binding of K* K*bar 5-45 MeV deeper. The plausible interpretation of f_0(1710) and X(1812) being K* K*bar dominated states is briefly discussed.

nucl-th↗

arXiv2007

Four-quark Bound States in Chiral SU(3) Quark Model

The possibility of $QQ\bar{q}\bar{q}$ heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where $Q$ is the heavy quark ($c$ or $b$) and $q$ is the light quark ($u$, $d$ or $s$). We obtain a bound state for the $bb\bar{n}\bar{n}$ configuration with quantum number $J^{P}=1^{+},I=0$ and for the $cc\bar{n}\bar{n}$ ($J^{P}=1^{+},I=0$) configuration which is not bound but slightly above the $D^{*}D^{*}$ threshold (n is $u$ or $d$ quark). Meanwhile, we also conclude that a weakly bound state in $bb\bar{n}\bar{n}$ system can also be found without considering the chiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions.

nucl-th↗

arXiv2007

Preliminary study of the anti-K N interaction in a chiral constituent quark model

A preliminary investigation of the anti-K N interaction is performed within a chiral constituent quark model by solving the resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the S-, P-, D-, F-wave KN scattering phase shifts. The channel-coupling between anti-K N, pi Lambda and pi Sigma is considered, and the scattering phase shifts as well as the bound-state problem of anti-K N are dynamically studied. The results show that the S-wave anti-K N interaction in the isospin I=0 channel is attractive, and in the extended chiral SU(3) quark model such an attraction can make for an anti-K N bound state, which appears as a pi Sigma resonance in the coupled-channel calculation, while the chiral SU(3) quark model cannot accommodate the existence of an anti-K N bound state. It seems that the vector meson exchanges are necessary to be introduced in the quark-quark interactions if one tries to explain the Lambda(1405) as an anti-K N bound state or a pi Sigma - anti-K N resonance state.

nucl-th↗

arXiv2007

$Qq\bar Q\bar q'$ States in Chiral SU(3) Quark Model

In this work, we study the masses of $Qq\bar Q\bar q'$ states with J^{PC}=0^{++}, 1^{++}, 1^{+-} and 2^{++} in the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q (q') is the light quark (u, d or s). According to our numerical results, it is improbable to make the interpretation of $[cn\bar c\bar n]_{1^{++}}$ and $[cn\bar c\bar n]_{2^{++}}$ (n=u, d) states as X(3872) and Y(3940), respectively. However, it is interesting to find the tetraquarks in the $bq\bar b\bar q'$ system.

hep-ph↗

arXiv2007

Low-lying ud anti-s anti-s configurations in a non-relativistic constituent quark model

The energies of the low-lying isoscalar and isovector ud anti-s anti-s configurations with spin-parity J^P=0^+, 1^+, and 2^+ are calculated in a non-relativistic constituent quark model by use of the variational method. The contributions of various parts of the quark-quark interacting potentials including the s-channel interaction are investigated, and the effect of different forms of confinement potential is examined. The model parameters are determined by the same method as in our previous work, and they still can satisfactorily describe the nucleon-nucleon scattering phase shifts and the hyperon-nucleon cross sections. The parameters of the s-channel interaction are fixed by the masses of K and K^* mesons, for which the size parameter is taken to be two possible values. When it is chosen as the same as baryons', the numerical results show that the masses of all the ud anti-s anti-s configurations are higher than the corresponding meson-meson thresholds. But when the size parameter for the K and K^* mesons is adjusted to be smaller than that for the baryons, the ud anti-s anti-s configuration with I=0 and J^P=1^+ is found to lie lower than the K^*K^* threshold, furthermore, this state has a very small KK^* component and the interaction matrix elements between this state and KK^* is comparatively small, thus its coupling to the KK^* channel will consequently be weak and it might be regarded as a possible tetraquark candidate.

nucl-th↗

arXiv2006

Chiral SU(3) Quark Model Study of Tetraquark States: $cn\bar{n}\bar{s} / cs\bar{s}\bar{s}$

The new members of the charm-strange family $D_{sJ}^{*}(2317)$, $D_{sJ}(2460)$ and $D_s(2632)$, which have the surprising properties, are challenging the present models. Many theoretical interpretations have been devoted to this issue. Most of authors suggest that they are not the conventional $c\bar s$ quark model states, but possibly are four-quark states, molecule states or mixtures of a P-wave $c\bar s$ and a four-quark state. In this work, we follow the four-quark-state picture, and study the masses of $cn\bar n\bar s/cs\bar s\bar s$ states ($n$ is $u$ or $d$ quark) in the chiral SU(3) quark model. The numerical results show that the mass of the mixed four-quark state ($cn\bar n\bar s/cs\bar s\bar s$) with spin parity $J^P=0^{+}$ might not be $D_s(2632)$. At the same time, we also conclude that $D_{sJ}^{*}(2317)$ and $D_{sJ}(2460)$ cannot be explained as the pure four-quark state.

hep-ph↗

arXiv2006

A possible Omega-pi molecular state

The structure of Omega-pi state with isospin I=1 and spin-parity J^p=3/2^- are dynamically studied in both the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the energies of the baryon ground states, the binding energy of the deuteron, the nucleon-nucleon (NN) scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The calculated results show that the Omega-pi state has an attractive interaction, and in the extended chiral SU(3) quark model such an attraction can make for an Omega-pi quasi-bound state with the binding energy of about several MeV.

nucl-th↗

arXiv2006

Study on N Omega-bar systems in a chiral quark model

The N Omega-bar systems with spin S=1 and S=2 are dynamically investigated within the framework of the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving the resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a good description of the energies of the baryon ground states, the binding energy of deuteron, and the experimental data of the nucleon-nucleon (NN) and nucleon-hyperon (NY) scattering processes. The results show that N Omega-bar states with spin S=1 and S=2 can be bound both in the chiral SU(3) and extended chiral SU(3) quark models, and the binding energies are about 28-59 MeV. When the annihilation effect is considered, the binding energies increase to about 37-130 MeV, which indicates the annihilation effect plays a relatively important role in forming an N Omega-bar bound state. At the same time, the N Omega-bar elastic scattering processes are also studied. The S, P, D partial wave phase shifts and the total cross sections of S=1 and S=2 channels have been calculated by solving the RGM equation for scattering problems.

nucl-th↗

arXiv2006

Baryon-meson interactions in chiral quark model

Using the resonating group method (RGM), we dynamically study the baryon-meson interactions in chiral quark model. Some interesting results are obtained: (1) The Sigma K state has an attractive interaction, which consequently results in a Sigma K quasibound state. When the channel coupling of Sigma K and Lambda K is considered, a sharp resonance appears between the thresholds of these two channels. (2) The interaction of Delta K state with isospin I=1 is attractive, which can make for a Delta K quasibound state. (3) When the coupling to the Lambda K* channel is considered, the N phi is found to be a quasibound state in the extended chiral SU(3) quark model with several MeV binding energy. (4) The calculated S-, P-, D-, and F-wave KN phase shifts achieve a considerable improvement in not only the signs but also the magnitudes in comparison with other's previous quark model study.

nucl-th↗

arXiv2005

Delta K, Lambda K, and Sigma K states in the extended chiral SU(3) quark model

By use of the resonating group method, the Delta K, Lambda K, and Sigma K states are further dynamically studied in the extended chiral SU(3) quark model based on our previous work. Similar to the results given by the original chiral SU(3) quark model, the calculated results here still show that the interactions of Delta K with isospin I=1 and Sigma K with isospin I=1/2 are attractive, which can consequently lead to Delta K and Sigma K quasibound states. When the channel coupling of Lambda K and Sigma K is considered, the calculated phase shifts show a sharp resonance between the thresholds of these two channels with spin-parity J^P=1/2^-.

nucl-th↗

arXiv2005

N K Pi molecular state with I=1 and J(Pi)=3/2-

The structure of the molecule-like state of $NKπ$ with spin-parity $J^π={3/2}^-$ and isospin I=1 is studied within the chiral SU(3) quark model. First we calculate the $NK$, $Nπ$, and $Kπ$ phase shifts in the framework of the resonating group method (RGM), and a qualitative agreement with the experimental data is obtained. Then we perform a rough estimation for the energy of $(NKπ)_{J^π={3/2}^-,I=1}$, and the effect of the mixing to the configuration $(ΔK)_{J^π={3/2}^-,I=1}$ is also considered. The calculated energy is very close to the threshold of the $NKπ$ system. A detailed investigation is worth doing in the further study.

hep-ph↗