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Saadaoui, H.; Morris, G. D.; Salman, Z.; Song, Q.; Chow, K. H.; Hossain, M. D.; Levy, C.D.P.; Parolin, T. J.; Pearson, M. R.; Smadella, M.; Wang, D.; Greene, L. H.; Hentges, P.; Kiefl, R. F.; MacFarlane, W. A.

doi:10.1103/physrevb.83.054504

Cited by 21 publications

(12 citation statements)

References 41 publications

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“…On the other hand, the establishment of a time-reversal symmetry breaking phase remains under discussion, see for instance refs. 40,41 . Several tunneling experiments on YBCO 42–44 show a split of the zero-bias conductance peak, while others do not 45,46 .…”

Section: Discussionmentioning

confidence: 99%

Broken translational symmetry at edges of high-temperature superconductors

et al. 2018

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Flat bands of zero-energy states at the edges of quantum materials have a topological origin. However, their presence is energetically unfavorable. If there is a mechanism to shift the band to finite energies, a phase transition can occur. Here we study high-temperature superconductors hosting flat bands of midgap Andreev surface states. In a second-order phase transition at roughly a fifth of the superconducting transition temperature, time-reversal symmetry and continuous translational symmetry along the edge are spontaneously broken. In an external magnetic field, only translational symmetry is broken. We identify the order parameter as the superfluid momentum ps, that forms a planar vector field with defects, including edge sources and sinks. The critical points of the vector field satisfy a generalized Poincaré-Hopf theorem, relating the sum of Poincaré indices to the Euler characteristic of the system.

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Section: Discussionmentioning

confidence: 99%

Broken translational symmetry at edges of high-temperature superconductors

et al. 2018

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“…Both of these order parameters produce a fully gapped state. Experimental data have, however, largely been contradictory, invoking large imaginary subdominant orders to explain tunneling experiments in YBa 2 Cu 3 O 7−δ (YBCO) [164,165] and La 2−x Sr x CuO 4 [166] or thermal conductivity in Bi 2 Sr 2 CaCu 2 O 8 [167], but, on the other hand, only very small imaginary components seem compatible with the absence of any measured spontaneous magnetization [60,[168][169][170][171]. Recent experiments on nanoscale YBCO islands have shown a small, but measurable, energy gap of size 20-40 µeV [172], which was subsequently theoretically identified to be due to a subdominant s-wave order supported on the island surfaces [173].…”

Section: D-wave Superconductorsmentioning

confidence: 98%

Dirac materials

Wehling¹,

Black‐Schaffer²,

Balatsky³

2014

Advances in Physics

915

864

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A wide range of materials, like d-wave superconductors, graphene, and topological insulators, share a fundamental similarity: their low-energy fermionic excitations behave as massless Dirac particles rather than fermions obeying the usual Schrödinger Hamiltonian. This emergent behavior of Dirac fermions in condensed matter systems defines the unifying framework for a class of materials we call "Dirac materials". In order to establish this class of materials, we illustrate how Dirac fermions emerge in multiple entirely different condensed matter systems and we discuss how Dirac fermions have been identified experimentally using electron spectroscopy techniques (angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy). As a consequence of their common low-energy excitations, this diverse set of materials shares a significant number of universal properties in the lowenergy (infrared) limit. We review these common properties including nodal points in the excitation spectrum, density of states, specific heat, transport, thermodynamic properties, impurity resonances, and magnetic field responses, as well as discuss many-body interaction effects. We further review how the emergence of Dirac excitations is controlled by specific symmetries of the material, such as time-reversal, gauge, and spin-orbit symmetries, and how by breaking these symmetries a finite Dirac mass is generated. We give examples of how the interaction of Dirac fermions with their distinct real material background leads to rich novel physics with common fingerprints such as the suppression of back scattering and impurity-induced resonant states. PACS

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“…Most of the work concentrated on description of subdominant pairing channels, as a way of identifying the symmetry and origin of the pairing state in cuprates, since unusual surface properties can give clear signature of such pairing states. [62][63][64][65] In superfluid 3 He, that has one of the most complex order parameter structures out of all known superconductors, investigation of Andreev surface states is particularly interesting. Despite extensive work, up to date there have been few experiments directly testing their presence.…”

Section: Experimental Investigation Of Thin Filmsmentioning

confidence: 99%

Andreev bound states in superconducting films and confined superfluid ³ He

Vorontsov

2018

Phil. Trans. R. Soc. A.

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This paper reviews confinement-driven phase transitions in superconductors and Bardeen-Cooper-Schrieffer superfluids, and the appearance in thin films of new phases that break the time-reversal or translational symmetry. The origins of the new phases are closely tied to the Andreev scattering processes involving particle-hole conversions that create surface quasiparticle states with energies inside the superconducting gap. Restructuring of the low-energy spectrum in the surface region of several coherence lengths results in large spatial variations of the superconducting order parameter. In confined geometry, such as slabs, films, pores or nano-dots, with one or more physical dimensions∼10, the Andreev bound states can dominate properties of a superconductor, leading to modified experimental signatures. They can significantly change the energy landscape, and drive transitions into new superconducting phases. The new phases are expected in a variety of materials, from singlet -wave superconductors to multi-component triplet superfluidHe, but properties of the new phases will depend on the symmetry of the parent state. I will highlight the connection between the Andreev surface states and confinement-stabilized phases with additional broken symmetries, describe recent progress and open questions in the theoretical and experimental investigation of superfluids in confined geometry.This article is part of the theme issue 'Andreev bound states'.

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Search for broken time-reversal symmetry near the surface of superconducting YBa2Cu3O
H. Saadaoui
¹
,
G. D. Morris
²
,
Z. Salman
³

et al.

Cited by 21 publications

References 41 publications

Broken translational symmetry at edges of high-temperature superconductors

Broken translational symmetry at edges of high-temperature superconductors

Dirac materials

Andreev bound states in superconducting films and confined superfluid ³ He

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Search for broken time-reversal symmetry near the surface of superconducting YBa2Cu3OH. Saadaoui1, G. D. Morris2, Z. Salman3 et al.

Cited by 21 publications

References 41 publications

Broken translational symmetry at edges of high-temperature superconductors

Broken translational symmetry at edges of high-temperature superconductors

Dirac materials

Andreev bound states in superconducting films and confined superfluid 3 He

Contact Info

Product

Resources

About

Search for broken time-reversal symmetry near the surface of superconducting YBa2Cu3O
H. Saadaoui
¹
,
G. D. Morris
²
,
Z. Salman
³

et al.

Andreev bound states in superconducting films and confined superfluid ³ He