New ground states in unconventional superconductors: Broken translational and time-reversal symmetry

1992 ◽  
Vol 45 (21) ◽  
pp. 12620-12623 ◽  
Author(s):  
Mario Palumbo ◽  
Paul Muzikar
Keyword(s):  
Time Reversal ◽  
Ground States ◽  
Time Reversal Symmetry ◽  
Unconventional Superconductors

scholarly journals DMRG study of strongly interacting $\mathbb{Z}_2$ flatbands: a toy model inspired by twisted bilayer graphene

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Paul Eugenio ◽  
Ceren Dag
Keyword(s):  
Magnetic Field ◽  
Time Reversal ◽  
Ground States ◽  
Bilayer Graphene ◽  
Chern Number ◽  
Strong Interactions ◽  
Time Reversal Symmetry ◽  
Density Matrix Renormalization ◽  
Topological Quantum ◽  
Twisted Bilayer Graphene

Strong interactions between electrons occupying bands of opposite (or like) topological quantum numbers (Chern=\pm1=±1), and with flat dispersion, are studied by using lowest Landau level (LLL) wavefunctions. More precisely, we determine the ground states for two scenarios at half-filling: (i) LLL’s with opposite sign of magnetic field, and therefore opposite Chern number; and (ii) LLL’s with the same magnetic field. In the first scenario – which we argue to be a toy model inspired by the chirally symmetric continuum model for twisted bilayer graphene – the opposite Chern LLL’s are Kramer pairs, and thus there exists time-reversal symmetry (\mathbb{Z}_2ℤ2). Turning on repulsive interactions drives the system to spontaneously break time-reversal symmetry – a quantum anomalous Hall state described by one particle per LLL orbital, either all positive Chern |{++\cdots+}\rangle|++⋯+⟩ or all negative |{--\cdots-}\rangle|−−⋯−⟩. If instead, interactions are taken between electrons of like-Chern number, the ground state is an SU(2)SU(2) ferromagnet, with total spin pointing along an arbitrary direction, as with the \nu=1ν=1 spin-\frac{1}{2}12 quantum Hall ferromagnet. The ground states and some of their excitations for both of these scenarios are argued analytically, and further complimented by density matrix renormalization group (DMRG) and exact diagonalization.

Search for time-reversal symmetry breaking in unconventional superconductors

2009 ◽  
Vol 404 (3-4) ◽  
pp. 507-509 ◽  
Author(s):  
Aharon Kapitulnik ◽  
Jing Xia ◽  
Elizabeth Schemm
Keyword(s):  
Symmetry Breaking ◽  
Time Reversal ◽  
Time Reversal Symmetry ◽  
Unconventional Superconductors

scholarly journals Polar Kerr effect as probe for time-reversal symmetry breaking in unconventional superconductors

2009 ◽  
Vol 11 (5) ◽  
pp. 055060 ◽  
Author(s):  
Aharon Kapitulnik ◽  
Jing Xia ◽  
Elizabeth Schemm ◽  
Alexander Palevski
Keyword(s):  
Symmetry Breaking ◽  
Time Reversal ◽  
Kerr Effect ◽  
Time Reversal Symmetry ◽  
Unconventional Superconductors ◽  
Polar Kerr Effect

scholarly journals Dynamics of time-reversal-symmetry-breaking vortices in unconventional superconductors

1998 ◽  
Vol 57 (2) ◽  
pp. R724-R727 ◽  
Author(s):  
Z. D. Wang ◽  
Qiang-Hua Wang
Keyword(s):  
Symmetry Breaking ◽  
Time Reversal ◽  
Time Reversal Symmetry ◽  
Unconventional Superconductors

Broken time reversal symmetry in unconventional superconductors

2000 ◽  
Vol 341-348 ◽  
pp. 695-698 ◽  
Author(s):  
Manfred Sigrist
Keyword(s):  
Time Reversal ◽  
Time Reversal Symmetry ◽  
Unconventional Superconductors

scholarly journals Correlated ground states with (spontaneously) broken time-reversal symmetry

1997 ◽  
Vol 104 (4) ◽  
pp. 227-231 ◽  
Author(s):  
Behnam Farid
Keyword(s):  
Time Reversal ◽  
Ground States ◽  
Time Reversal Symmetry

scholarly journals Re1−xMox as an ideal test case of time-reversal symmetry breaking in unconventional superconductors

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Tian Shang ◽  
Christopher Baines ◽  
Lieh-Jeng Chang ◽  
Dariusz Jakub Gawryluk ◽  
Ekaterina Pomjakushina ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Spin Relaxation ◽  
Time Reversal ◽  
Gradual Increase ◽  
Muon Spin ◽  
Superconducting Phase ◽  
Test Case ◽  
Time Reversal Symmetry ◽  
Key Factors ◽  
Unconventional Superconductors

Abstract Non-centrosymmetric superconductors (NCSCs) are promising candidates in the search for unconventional and topological superconductivity. The α-Mn-type rhenium-based alloys represent excellent examples of NCSCs, where spontaneous magnetic fields, peculiar to time-reversal symmetry (TRS) breaking, have been shown to develop in the superconducting phase. By converse, TRS is preserved in many other isostructural NCSCs, thus leaving the key question about its origin fully open. Here, we consider the superconducting Re1−xMox (0 ≤ x ≤ 1) family, which comprises both centro- and non-centrosymmetric structures and includes also two extra superconducting phases, β-CrFe and bcc-W. Muon-spin relaxation and rotation (μSR) measurements show a gradual increase of the relaxation rate below Tc, yet its independence of the crystal structure, suggesting that rhenium presence and its amount are among the key factors for the appearance and the extent of TRS breaking in the α-Mn-type NCSCs. The reported results propose Re1−xMox as an ideal test case for investigating TRS breaking in unconventional superconductors.

scholarly journals Supercurrents and spontaneous time-reversal symmetry breaking by nonmagnetic disorder in unconventional superconductors

2022 ◽  
Vol 105 (1) ◽  
Author(s):  
Clara N. Breiø ◽  
P. J. Hirschfeld ◽  
Brian M. Andersen
Keyword(s):  
Symmetry Breaking ◽  
Time Reversal ◽  
Time Reversal Symmetry ◽  
Unconventional Superconductors

scholarly journals Dirac lines and loop at the Fermi level in the time-reversal symmetry breaking superconductor LaNiGa2

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Jackson R. Badger ◽  
Yundi Quan ◽  
Matthew C. Staab ◽  
Shuntaro Sumita ◽  
Antonio Rossi ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Fermi Level ◽  
Time Reversal ◽  
Orbit Coupling ◽  
Time Reversal Symmetry ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Electronic Band ◽  
Unconventional Superconductors ◽  
Topological Features

AbstractUnconventional superconductors have Cooper pairs with lower symmetries than in conventional superconductors. In most unconventional superconductors, the additional symmetry breaking occurs in relation to typical ingredients such as strongly correlated Fermi liquid phases, magnetic fluctuations, or strong spin-orbit coupling in noncentrosymmetric structures. In this article, we show that the time-reversal symmetry breaking in the superconductor LaNiGa2 is enabled by its previously unknown topological electronic band structure, with Dirac lines and a Dirac loop at the Fermi level. Two symmetry related Dirac points even remain degenerate under spin-orbit coupling. These unique topological features enable an unconventional superconducting gap in which time-reversal symmetry can be broken in the absence of other typical ingredients. Our findings provide a route to identify a new type of unconventional superconductors based on nonsymmorphic symmetries and will enable future discoveries of topological crystalline superconductors.

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