Chiral universality class of normal-superconducting and exciton condensation transitions on surface of topological insulator  

作　　者：Dingping Li Baruch Rosenstein B. Ya. Shapiro I. Shapiro 

机构地区：[1]School of Physics, Peking University, Beijing 100871, China [2]Collaborative Innovation Center of Quantum Matter, Beijing 100084, China [3]Electrophysics Department, National Chiao Tung University, Hsinchu 30050, Taiwan, China [4]physics Department, Ariel University, Ariel 40700, Israel [5]Physics Department, Bar-Ilan University, 52900 Ramat-Gan, Israel

出　　处：《Frontiers of physics》2015年第3期65-82,共18页物理学前沿（英文版）

基　　金：Acknowledgements We are indebted to C. W. Luo, J. J. Lin, and W. B. Jian for explaining the details of their experiments, and T. Maniv and M. Lewkowicz for valuable discussions. The work of D. Li and B. Rosenstein was supported by the NSC of Taiwan, China, Grant No. 98-2112-M-009-014-MY3, and the MOE ATU program. The work of D. Li was also supported by the National Natural Science Foundation of China （Grant No. 11274018）. B. Rosenstein was grateful to the School of Physics of Peking University for its hospitality.

摘　　要：New two-dimensional systems such as the surfaces of topological insulators （TIs） and graphene offer the possibility of experimentally investigating situations considered exotic just a decade ago. These situations include the quantum phase transition of the chiral type in electronic systems with a relativistic spectrum. Phonon-mediated （conventional） pairing in the Dirac semimetal appearing on the surface of a TI causes a transition into a chiral superconducting state, and exciton condensation in these gapless systems has long been envisioned in the physics of narrow-band semiconductors. Starting from the microscopic Dirac Hamiltonian with local attraction or repulsion, the Bardeen- Cooper-Schrieffer type of Gaussian approximation is developed in the framework of functional integrals. It is shown that owing to an ultrarelativistic dispersion relation, there is a quantum critical point governing the zero-temperature transition to a superconducting state or the exciton condensed state. Quantum transitions having critical exponents differ greatly from conventional ones and belong to the chiral universality class. We discuss the application of these results to recent experiments in which surface superconductivity was found in TIs and estimate the feasibility of phonon pairing.New two-dimensional systems such as the surfaces of topological insulators （TIs） and graphene offer the possibility of experimentally investigating situations considered exotic just a decade ago. These situations include the quantum phase transition of the chiral type in electronic systems with a relativistic spectrum. Phonon-mediated （conventional） pairing in the Dirac semimetal appearing on the surface of a TI causes a transition into a chiral superconducting state, and exciton condensation in these gapless systems has long been envisioned in the physics of narrow-band semiconductors. Starting from the microscopic Dirac Hamiltonian with local attraction or repulsion, the Bardeen- Cooper-Schrieffer type of Gaussian approximation is developed in the framework of functional integrals. It is shown that owing to an ultrarelativistic dispersion relation, there is a quantum critical point governing the zero-temperature transition to a superconducting state or the exciton condensed state. Quantum transitions having critical exponents differ greatly from conventional ones and belong to the chiral universality class. We discuss the application of these results to recent experiments in which surface superconductivity was found in TIs and estimate the feasibility of phonon pairing.

关 键 词：topological insulator Weyl semimetal SUPERCONDUCTIVITY quantum criticality 

分 类 号：O643.36[理学—物理化学] TS941.717[理学—化学]