arXiv subjects

Jing-Rong Wang

Publications and source records attributed to Jing-Rong Wang.

44 records · Page 3Linked to original sources

arXiv2012

Absence of dynamical gap generation in suspended graphene

There is an interesting proposal that the long-range Coulomb interaction in suspended graphene can generate a dynamical gap, which leads to a semimetal-insulator phase transition. We revisit this problem by solving the self-consistent Dyson-Schwinger equations of wave function renormalization and fermion gap. In order to satisfy the Ward identity, a suitable vertex function is introduced. The impacts of singular velocity renormalization and dynamical screening on gap generation are both included in this formalism, and prove to be very important. We obtain a critical interaction strength, $3.2 < α_{c} < 3.3$, which is larger than the physical value $α= 2.16$ for suspended graphene. It therefore turns out that suspended graphene is a semimetal, rather than insulator, at zero temperature.

cond-mat.str-el↗

arXiv2011

Nature of the antiferromagnetic quantum phase transition on the honeycomb lattice

We address the nature of the antiferromagnetic quantum phase transition that separates a semimetal from an antiferromagnet in the repulsive Hubbard model defined on the honeycomb lattice. At the critical point, the fermions acquire an anomalous dimension $η$ due to their strong coupling to the fluctuations of the order parameter $ϕ$. The finite $η$ in turn induces a singular $ϕ^{4}$ term and a non-analytical spin susceptibility signaling the breakdown of Hertz's $ϕ^{4}$ theory. As a result, the continuous antiferromagnetic quantum phase transition is internally unstable and turns into a first order transition.

cond-mat.str-el↗

arXiv2011

Eliashberg theory of excitonic insulating transition in graphene

A sufficiently strong Coulomb interaction may open an excitonic fermion gap and thus drive a semimetal-insulator transition in graphene. In this paper, we study the Eliashberg theory of excitonic transition by coupling the fermion gap equation self-consistently to the equation of vacuum polarization function. Including the fermion gap into polarization function increases the effective strength of Coulomb interaction because it reduces the screening effects due to the collective particle-hole excitations. Although this procedure does not change the critical point, it leads to a significant enhancement of the dynamical fermion gap in the excitonic insulating phase. The validity of the Eliashberg theory is justified by showing that the vertex corrections are suppressed at large $N$ limit.

cond-mat.str-el↗

arXiv2011

Competition between excitonic gap generation and disorder scattering in graphene

We study the disorder effect on the excitonic gap generation caused by strong Coulomb interaction in graphene. By solving the self-consistently coupled equations of dynamical fermion gap $m$ and disorder scattering rate $Γ$, we found a critical line on the plane of interaction strength $λ$ and disorder strength $g$. The phase diagram is divided into two regions: in the region with large $λ$ and small $g$, $m \neq 0$ and $Γ= 0$; in the other region, $m = 0$ and $Γ\neq 0$ for nonzero $g$. In particular, there is no coexistence of finite fermion gap and finite scattering rate. These results imply a strong competition between excitonic gap generation and disorder scattering. This conclusion does not change when an additional contact four-fermion interaction is included. For sufficiently large $λ$, the growing disorder may drive a quantum phase transition from an excitonic insulator to a metal.

cond-mat.str-el↗

arXiv2010

Confinement induced by fermion damping in three-dimensional QED

The three-dimensional non-compact QED is known to exhibit weak confinement when fermions acquire a finite mass via the mechanism of dynamical chiral symmetry breaking. In this paper, we study the effect of fermion damping caused by elastic scattering on the classical potential between fermions. By calculating the vacuum polarization function that incorporates the fermion damping effect, we show that fermion damping can induce a weak confinement even when the fermions are massless and the chiral symmetry is not broken.

hep-th↗

arXiv2010

Fate of non-Fermi liquid behavior in QED$_{3}$ at finite chemical potential

The damping rate of two-dimensional massless Dirac fermions exhibit non-Fermi liquid behavior, $\propto ε^{1/2}$, due to gauge field at zero temperature and zero chemical potential. We study the fate of this behavior at finite chemical potential. We fist calculate explicitly the temporal and spatial components of vacuum polarization functions. The analytical expressions imply that the temporal component of gauge field develops a static screening length at finite chemical potential while the transverse component remains long-ranged owing to gauge invariance. We then calculate the fermion damping rate and show that the temporal gauge field leads to normal Fermi liquid behavior but the transverse gauge field leads to non-Fermi liquid behavior $\propto ε^{2/3}$ at zero temperature. This energy-dependence is more regular than $\propto ε^{1/2}$ and does not change as chemical potential varies.

cond-mat.str-el↗

arXiv2010

Unconventional Fermi surface in two-dimensional systems of Dirac fermions

At the low energy regime, the decay rate of two-dimensional massless Dirac fermions due to interactions can be written as $\mathrm{Im}Σ(ω) \propto |ω|^{x}$ at zero temperature. We find that the fermion system has: I) no sharp Fermi surface and no well-defined quasiparticle peak for $0 1$. In the presence of long-range gauge/Coulomb interaction or certain massless boson mode, the system exhibits unusual behavior belonging to class II.

cond-mat.str-el↗

arXiv2010

Non-Fermi liquid behavior due to U(1) gauge field in two dimensions

We study the damping rate of massless Dirac fermions due to the U(1) gauge field in (2+1)-dimensional quantum electrodynamics. In the absence of a Maxwell term for the gauge field, the fermion damping rate $\mathrm{Im}Σ(ω,T)$ is found to diverge in both perturbative and self-consistent results. In the presence of a Maxwell term, there is still divergence in the perturbative results for $\mathrm{Im}Σ(ω,T)$. Once the Maxwell term is included into the self-consistent equations for fermion self-energy and vacuum polarization functions, the fermion damping rate is free of divergence and exhibits non-Fermi liquid behavior: $\mathrm{Im}Σ(ω,T) \propto \mathrm{max}(\sqrtω,\sqrt{T})$.

cond-mat.supr-con↗