Fractional Josephson effect in nonuniformly strained graphene

Lee, Shu-Ping; Nandi, Debaleena; Marsiglio, F.; Maciejko, Joseph

doi:10.1103/physrevb.95.174517

Cited by 10 publications

(7 citation statements)

References 35 publications

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“…The first is to test other properties associated with pseudo-Landau levels. Recent work on the fractional Josephson effect in strained 2D graphene superconductor [52] motivates the interest in studying a similar effect in one dimension higher using strained Weyl superconductor. The second lies in the study of the chiral anomaly, chiral magnetic effect, and gravitational anomaly with straininduced gauge field.…”

Section: Discussionmentioning

confidence: 99%

Quantum oscillations and Dirac-Landau levels in Weyl superconductors

2017

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When magnetic field is applied to metals and semimetals quantum oscillations appear as individual Landau levels cross the Fermi level. Quantum oscillations generally do not occur in superconductors (SC) because magnetic field is either expelled from the sample interior or, if strong enough, drives the material into the normal state. In addition, elementary excitations of a superconductor -- Bogoliubov quasiparticles -- do not carry a well defined electric charge and therefore do not couple in a simple way to the applied magnetic field. We predict here that in Weyl superconductors certain types of elastic strain have the ability to induce chiral pseudo-magnetic field which can reorganize the electronic states into Dirac-Landau levels with linear band crossings at low energy. The resulting quantum oscillations in the quasiparticle density of states and thermal conductivity can be experimentally observed under a bending deformation of a thin film Weyl SC and provide new insights into this fascinating family of materials.Comment: Version accepted by PRB, minor changes, references adde

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Section: Discussionmentioning

confidence: 99%

Quantum oscillations and Dirac-Landau levels in Weyl superconductors

2017

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“…These microscopic strain models are relevant for a wide range of applications, including: straintronics 43 , that is, engineering the strain field to obtain the desired electronic properties such as band gaps and effective masses; the realization of stretchable electronic devices based on the layered materials 64 ; exploiting the interplay between moiré patterns, commensurate-incommensurate transitions 65 and distortions 66 which result from twisted bilayer structure that already strongly modifies the monolayer Dirac dispersion and induces insulating states from the superlattice 67 ; exploring the effects of topological lattice defects 1,68 ; induced interference effects from lattice deformation 69 ; understanding of electronic scattering and mobility from lattice deformations. The pseudo magnetic field, that does not break time-reversal symmetry, induced by the strain field may be utilized to probe many-body physics through the quantum oscillations without magnetic field 70 , or fractional Josephson effect when coupled with a superconductor 71 . Beyond the applications involving static strain fields, we also expect that our microscopic analysis is applicable to the dynamical strain field generated by oscillating acoustic waves 72 , which can be used as an experimental probe of other excitations in materials, or as a means to realize periodically modulated Floquet Hamiltonians, which will be relevant for studies of non-equilibrium or topological phases 73 .…”

Section: B Transition Metal Dichalcogenidesmentioning

confidence: 99%

Electronic structure theory of strained two-dimensional materials with hexagonal symmetry

et al. 2018

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We derive electronic tight-binding Hamiltonians for strained graphene, hexagonal boron nitride and transition metal dichalcogenides based on Wannier transformation of ab initio density functional theory calculations. Our microscopic models include strain effects to leading order that respect the hexagonal crystal symmetry and local crystal configuration, and are beyond the central force approximation which assumes only pair-wise distance dependence. Based on these models, we also derive and analyze the effective low-energy Hamiltonians. Our ab initio approaches complement the symmetry group representation construction for such effective low-energy Hamiltonians and provide the values of the coefficients for each symmetry-allowed term. These models are relevant for the design of electronic device applications, since they provide the framework for describing the coupling of electrons to other degrees of freedom including phonons, spin and the electromagnetic field. The models can also serve as the basis for exploring the physics of many-body systems of interesting quantum phases. PACS numbers: 71.15.-m, 73.22.-f, 74.78.Fk, arXiv:1709.07510v2 [cond-mat.mes-hall] 12 Aug 2018 0.273 −0.043 0.720 0.270 0.004 0.829 0.487 0.036 1.586 0.482 −0.022 1.507

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“…In this situation, electrons in different valleys feel opposite directions of the magnetic field. Strained graphene gives the unique opportunity to study proximity-induced superconductivity under strong magnetic field without suffering from degradation of the superconductivity [29][30][31][32][33].…”

Section: Discussionmentioning

confidence: 99%

Proximity coupling in superconductor-graphene heterostructures

Lee

2018

Rep. Prog. Phys.

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This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

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Fractional Josephson effect in nonuniformly strained graphene

Cited by 10 publications

References 35 publications

Quantum oscillations and Dirac-Landau levels in Weyl superconductors

Quantum oscillations and Dirac-Landau levels in Weyl superconductors

Electronic structure theory of strained two-dimensional materials with hexagonal symmetry

Proximity coupling in superconductor-graphene heterostructures

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