Frontiers in Synthetic Moiré Quantum Matter Proceedings of a Workshop (2022) / Chapter Skim
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Appendix C: Registered Workshop Participants
Appendix C: Registered Workshop Participants
Pages 74-82
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From page 74... ...
74 Frontiers in S y n t h e t i c M o i r é Q ua n t u m M at t e r straightforward to adjust the amount of oxygen in the layer via annealing, whereas with the bulk material one must produce many different samples in order to see how properties vary with changes in the amount of oxygen. "So what I'm going to talk about is basically grounded in reality," Franz said.
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From page 75... ...
Topological Superconductivity 75 places where the cloverleaf shape intersected the circle. By symmetry, he added, the d-wave order parameter is required to change sign upon a rotation by 90 degrees, so one lobe will be positive, and the lobes on either side of it will be negative, and because the gap is represented by a continuous function, its value has to be zero between a positive lobe and a negative lobe -- that is, along each diagonal.
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From page 76... ...
76 Frontiers in S y n t h e t i c M o i r é Q ua n t u m M at t e r Ginzburg-Landau Calculations The simplest way to model the situation, he said, is to use Ginzburg-Landau theory for calculating the free energy of a superconductor near the superconducting transition. The resulting equation, based on modeling the bilayer as two complex order parameters and writing all possible terms consistent with symmetry, has five terms.
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From page 77... ...
Topological Superconductivity 77 Continuum Bogoliubov–de Gennes Theory Next, Franz described some of the microscopic theory that lies the GinsburgLandua theory, specifically continuum Bogoliubov–de Gennes theory. His goal, he said, was just to describe some key points and not go into a lot of detail.
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From page 78... ...
78 Frontiers in S y n t h e t i c M o i r é Q ua n t u m M at t e r and on-site repulsion. In this case, he said, to make any headway one has to use commensurate twist angles.
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From page 79... ...
Topological Superconductivity 79 To probe for the breaking of time reversal symmetry, Franz said, Ye is planning to measure the polar Kerr effect, which is sensitive to time reversal symmetry breaking. The experiment involves shining polarized light on the sample and measuring the rotation of the polarization in the reflected light.
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80 Frontiers in S y n t h e t i c M o i r é Q ua n t u m M at t e r rial has time reversal symmetry broken in a region around the magic angle and close to 0 K In response to that work, Franz's team carried out some calculations of its own, and he showed a phase diagram that they calculated for the material assuming interaction-induced s-wave instability.
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From page 81... ...
Topological Superconductivity 81 This is known to host Majorana zero modes in the vortex core because this is a spin triplet superconductor with all of the symmetries. The drawback to this plan, Franz said, is that there are no such px + ipy superconductors known in nature.
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From page 82... ...
82 Frontiers in S y n t h e t i c M o i r é Q ua n t u m M at t e r because the band structures are so complicated. "Depending on where you look in the band structure," he said, "you get different answers for this quantity." As for the second question, Franz said that many of the calculations he showed were for BSCCO 2201, which is a cuprate with just a single copper–oxygen plane per monolayer, because they are simpler to do theoretically.
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