Competition between excitonic gap generation and disorder scattering in graphene

Liu, Guozhu; Wang, Jingrong

doi:10.1088/1367-2630/13/3/033022

Cited by 14 publications

(29 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since Nambu and Jona-Lasinio [68], the DS equation approach has been widely applied to study DCSB in QCD [123,124] and QED 3 [125][126][127][128][129][130][131]. It also has been used to examine whether an excitonic gap can be dynamically generated by the Coulomb interaction in graphene [65,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83] and other closely related materials [41,46,82]. The role played by the DS equation in the studies of excitonic gap generation is similar to that played by the gap equation in the studies of the formation of superconductivity in BCS theory.…”

Section: Dyson-schwinger Equation Of Excitnonic Gapmentioning

confidence: 99%

Excitonic pairing and insulating transition in two-dimensional semi-Dirac semimetals

Wang¹,

Liu²,

Zhang³

2017

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

A sufficiently strong long-range Coulomb interaction can induce excitonic pairing in gapless Dirac semimetals, which generates a finite gap and drives semimetal-insulator quantum phase transition. This phenomenon is in close analogy to dynamical chiral symmetry breaking in high energy physics. In most realistic Dirac semimetals, including suspended graphene, Coulomb interaction is too weak to open an excitonic gap. The Coulomb interaction plays a more important role at low energies in a two-dimensional semi-Dirac semimetal, in which the fermion spectrum is linear in one component of momenta and quadratic in the other, than a Dirac semimetal, and indeed leads to breakdown of Fermi liquid theory. We study dynamical excitonic gap generation in a two-dimensional semi-Dirac semimetal by solving the Dyson-Schwinger equation, and show that a moderately strong Coulomb interaction suffices to induce excitonic pairing. Additional short-range four-fermion coupling tends to promote excitonic pairing. Among the available semi-Dirac semimetals, we find that TiO2/VO2 nanostructure provides a promising candidate for the realization of excitonic insulator. We also apply the renormalziation group method to analyze the strong coupling between the massless semi-Dirac fermions and the quantum critical fluctuation of excitonic order parameter at the semimetal-insulator quantum critical point, and reveal non-Fermi liquid behaviors of semi-Dirac fermions.

show abstract

Section: Dyson-schwinger Equation Of Excitnonic Gapmentioning

confidence: 99%

Excitonic pairing and insulating transition in two-dimensional semi-Dirac semimetals

Wang¹,

Liu²,

Zhang³

2017

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, the strength of Coulomb interaction can be substantially reduced when the Dirac semimetal is placed on some metallic substrate [5][6][7]. Moreover, disorders may generate a finite DOS at the Dirac points, which also strongly suppresses the Coulomb interaction via static screening [14,15]. Therefore, it is in principle possible for Dirac semimetals to develop a net attractive interaction.…”

Section: Rg Calculations In Disordered Dirac Semimetalsmentioning

confidence: 99%

“…Extensive recent theoretic studies [3][4][5][6][7]10] have elaborated that the interparticle interactions can result in non-Fermi-liquid behaviors and certain quantum phase transition. For instance, the long-range Coulomb interaction is able to drive an excitonic insulating transition if its strength is sufficiently large [11][12][13][14][15][16]. The Coulomb interaction can also give rise to unusual spectral behaviors of Dirac fermions [5,6].…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in two-dimensional disordered Dirac semimetals

et al. 2017

Self Cite

View full text Add to dashboard Cite

In two-dimensional Dirac semimetals, Cooper pairing instability occurs only when the attractive interaction strength |u| is larger than some critical value |uc| because the density of states vanishes at Dirac points. Disorders enhance the low-energy density of states but meanwhile shorten the lifetime of fermions, which tend to promote and suppress superconductivity, respectively. To determine which of the two competing effects wins, we study the interplay of Cooper pairing interaction and disorder scattering by means of renormalization group method. We consider three types of disorders, including random mass, random gauge potential, and random chemical potential, and show that the first two suppress superconductivity. In particular, the critical BCS coupling |uc| is increased to certain larger value if the system contains only random mass or random gauge potential, which makes the onset of superconductivity more difficult. In the case of random chemical potential, the effective disorder parameter flows to the strong coupling regime, where the perturbation expansion breaks down and cannot provide a clear answer concerning the fate of superconductivity. When different types of disorder coexist in one system, their strength parameters all flow to strong couplings. In the strong coupling regime, the perturbative renormalization group method becomes invalid, and one needs to employ other methods to treat the disorder effects. We perform a simple gap equation analysis of the impact of random chemical potential on superconductivity by using the AbrikosovGorkov diagrammatic approach, and also briefly discuss the possible generalization of this approach.

show abstract

“…For these reasons, the dynamical gap generation and the resultant semimetal-insulator transition have attracted intense theoretical interest in recent years. Many analytical and computational tools, including the Dyson-Schwinger (DS) gap equation [19][20][21][22][23][24][25][26][27][28][29], the Bethe-Salpeter equation [30,31], renormalization group (RG) [32][33][34] and large-scale Monte Carlo simulation [35][36][37][38][39][40], have been applied to study this problem. A critical interaction strength α c and a critical fermion flavor N c are found in almost all these investigations: a dynamical gap is opened only when α > α c and N < N c .…”

Section: Introductionmentioning

confidence: 99%

Absence of dynamical gap generation in suspended graphene

Wang

Liu

2012

New J. Phys.

Self Cite

View full text Add to dashboard Cite

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 impact of singular velocity renormalization and that of 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 an insulator, at zero temperature.

show abstract

Competition between excitonic gap generation and disorder scattering in graphene

Cited by 14 publications

References 43 publications

Excitonic pairing and insulating transition in two-dimensional semi-Dirac semimetals

Excitonic pairing and insulating transition in two-dimensional semi-Dirac semimetals

Superconductivity in two-dimensional disordered Dirac semimetals

Absence of dynamical gap generation in suspended graphene

Contact Info

Product

Resources

About