Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X03: Topological Superconductors and SuperfluidsFocus

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Sponsoring Units: DCMP Room: BCEC 107B 
Friday, March 8, 2019 8:00AM  8:12AM 
X03.00001: Symmetryprotected line nodes and Majorana flat bands in nodal crystalline superconductors Shingo Kobayashi, Shuntaro Sumita, Youichi Yanase, Masatoshi Sato Over the last few years, the study on node structures in SCs has received renewed interest due to the fact that they are a kind of topological objects. In this context, a line node in timereversal (TR) invariant SCs is protected by a onedimensional (1D) topological number and induces a Majorana flat band (MFB) in a surface. The MFBs exhibit a zerobias conductance peak through the tunneling measurement for TR invariant SCs such as highTc SCs and noncentrosymmetric SCs, which gives a conclusive evidence for the bulk topological line nodes. 
Friday, March 8, 2019 8:12AM  8:24AM 
X03.00002: Full proximity approach to induced gap in topological superconductor junctions Fnu Setiawan, ChienTe Wu, Kathryn Levin Recently, a Josephson junction formed from a twodimensional electron gas (2DEG) proximitized by two superconductors subjected to an inplane magnetic field has emerged as a viable platform to realize topological superconductivity [13]. In this talk, we address the proximityinduced superconductivity in this setup by studying the full proximity model of a superconductorinsulatorsuperconductor junction in contact with a spinorbitcoupled substrate. To this end, we numerically solve the Bogoliubovde Gennes Hamiltonian of this model and study the effect of spinorbit coupling and thickness of the substrate on the induced pairing amplitude and energy dispersion. Finally, we will discuss the topological phase diagram of multiband topological Josephson junctions for a thick substrate. 
Friday, March 8, 2019 8:24AM  8:36AM 
X03.00003: Hot electron magnetotransport in the high mobility GaAs/AlGaAs two dimensional electron system below 1K C.Rasadi Munasinghe, Binuka Gunawardana, Rasanga Samaraweera, Tharanga Nanayakkara, U. Kushan Wijewardena, Sajith Withanage, Annika Kriisa, Christian Reichl, Werner Wegscheider, Ramesh Mani Nonequilibrium hot electron phenomena play a major role in semiconductor transport when, for example, the heat applied directly to the electronic system becomes substantial. The carrier temperature can differ from the lattice temperature, and the carrier temperature results, in the steady state, from a balance between energy gain from the heating source, and energy loss to the lattice from electronphonon scattering. In this experimental study, we examine heating induced by the small acbias current utilized in the lowfrequency lockin based four terminal transport measurements. Since at small bias current, the carrier heating is expected to be small, we have utilized an effect that is associated with a small energy scale to follow the heating effect, namely the spin splitting in the Shubnikovde Haas effect. The development of fields such as spintronics and spinbased quantum computing have encouraged further studies, such as this one, of the parameters affecting the behavior of electron spin in low dimensional electron systems. Thus, magnetotransport measurements have been carried out below 1K to observe the ac current effect on the characteristic features of the GaAs/AlGaAs system. In this report, we show evidence for a carrier heating effect due to the small ac bias. 
Friday, March 8, 2019 8:36AM  8:48AM 
X03.00004: Topological Phases in Nodeless Tetragonal Superconductors Santiago Varona, Laura Ortiz, Oscar Viyuela, Miguel Angel MartinDelgado We compute the topological phase diagram of 2D tetragonal superconductors for the only possible nodeless pairing channels compatible with that crystal symmetry. Subject to a Zeeman field and spinorbit coupling, we demonstrate that these superconductors show surprising topological features: nontrivial high Chern numbers, massive edge states, and zeroenergy modes out of high symmetry points, even though the edge states remain topologically protected. Interestingly, one of these pairing symmetries, d+id, has been proposed to describe materials such as waterintercalated sodium cobaltates, bilayer silicene or highly doped monolayer graphene. 
Friday, March 8, 2019 8:48AM  9:00AM 
X03.00005: Fractional Josephson Vortices and Braiding of Majorana Zero Modes in Planar SuperconductorSemiconductorSuperconductor Josephson junctions Ady Stern, Erez Berg We consider the onedimensional (1D) topological superconductor that may form in a planar superconductormetalsuperconductor Josephson junction in which the metal is is subjected to spin orbit coupling and to an inplane magnetic field. This 1D topological superconductor has been the subject of recent theoretical and experimental attention. We examine the effect of perpendicular magnetic field and a supercurrent driven across the junction on the position and structure of the Majorana zero modes that are associated with the topological superconductor. In particular, we show that under certain conditions the Josephson vortices fractionalize to halfvortices, each carrying half of the superconducting flux quantum and a single Majorana zero mode. Furthemore, we show that the system allows for a currentcontrolled braiding of Majorana zero modes. 
Friday, March 8, 2019 9:00AM  9:12AM 
X03.00006: An Exactly Solvable Interacting Edge Theory for a Weak 2D Topological Superconductor. Joseph Sullivan, Meng Cheng We study interacting edge states of a 2D weak topological superconductor protected by timereversal symmetry. Such a system can be viewed as a stack of Marjorana/Kitaev chains (class BDI), possessing translation symmetry in the transverse direction. Interestingly, in this model, timereversal symmetry forbids terms quadratic in fermionic degrees of freedom on the edge, so any edge dynamics must be inherently interacting. We proposed an exactly solvable model for the edge and worked out its phase diagram. It is shown that the edge is either symmetry breaking or gapless as expected from the bulkboundary correspondence of a topological phase. We then construct a low energy field theory for the model in the gapless phase. We propose that the same field theory describes the edge of an intrinsically interacting fermionic symmetryprotected phase with Z_4 x Z_2^T symmetry. 
Friday, March 8, 2019 9:12AM  9:24AM 
X03.00007: Majorana corner states in D class Xin Liu, XiaoHong Pan, KaiJie Yang Majorana corner states (MCSs) in D class can naturally form a topological qubit. In this talk, we show that how to realize MCSs in twodimensional topological insulators in the presence of both superconductivity and magnet. It is noted that there is only one MCS at each corner which is allowed due to the timereversal symmetry broken. An edge theory is performed to clearly demonstrate the physics behind these results. At last, we study the spin property of MCSs and propose to use spinresolved scanning tunneling microscope to detect their existence. 
Friday, March 8, 2019 9:24AM  9:36AM 
X03.00008: Generalized AubryAndréHarper model with pwave superconducting pairing QiBo Zeng, Shu Chen, Rong Lü We investigate a generalized AubryAndréHarper (AAH) model with pwave superconducting pairing. Both the hopping amplitudes between the nearestneighboring lattice sites and the onsite potentials in this system are modulated by a cosine function with a periodicity of 1/α. In the incommensurate case [α = (√5  1)/2], due to the modulations on the hopping amplitudes, the critical region of this quasiperiodic system is significantly reduced and the system becomes easier to be turned from extended states to localized states. In the commensurate case (α = 1/2), we find that this model shows three different phases when we tune the system parameters: SuSchriefferHeeger (SSH)like trivial, SSHlike topological, and Kitaevlike topological phases. The phase diagrams and the topological quantum numbers for these phases are presented in this work. This generalized AAH model combined with superconducting pairing provides us with a useful test field for studying the phase transitions from extended states to Anderson localized states and the transitions between different topological phases. 
Friday, March 8, 2019 9:36AM  9:48AM 
X03.00009: Conformal phase transition in topological superconductors Flavio Nogueira, Jeroen Van den Brink, Asle Sudbo A conformal phase transition (CPT) is a phase transition defining a critical point with a nonpower law diverging 
Friday, March 8, 2019 9:48AM  10:00AM 
X03.00010: Superconformal Cardy states and entanglement structure of 1D quantum critical points with emergent supersymmetry Chun Chen, Joseph Maciejko Condensed matter systems with quantum critical points exhibiting emergent spacetime supersymmetry in the longwavelength, lowenergy limit have attracted much attention recently. In particular, several elements of the N=1 series of superconformal minimal models originally discovered by Friedan, Qiu, and Shenker in 1985 have been realized recently in a variety of 1D quantum lattice models ranging from anyonic spin chains to interacting Majorana chains and bosonfermion mixtures. To better understand the entanglement structure of these exotic quantum critical points, we revisit the problem of the construction of boundary states for the superconformal minimal models and find a new set of Cardy states not previously discussed. As an application of this formalism we present and discuss numerical DMRG results for the entanglement spectrum of the GroverShengVishwanath model as a lattice realization of the tricritical Ising universality class. 
Friday, March 8, 2019 10:00AM  10:12AM 
X03.00011: Majorana Corner Modes in a HighTemperature Platform Zhongbo Yan, Fei Song, Zhong Wang We introduce twodimensional topological insulators in proximity to hightemperature cuprate or iron based superconductors as hightemperature platforms of Majorana Kramers pairs of zero modes. The proximityinduced pairing at the helical edge state of the topological insulator serves as a Dirac mass, whose sign changes at the sample corner because of the pairing symmetry of highTc superconductors. This sign changing naturally creates at each corner a pair of Majorana zero modes protected by timereversal symmetry. Conceptually, this is a topologically trivial superconductorbased approach for Majorana zero modes. We provide quantitative criteria and suggest candidate materials for this proposal.[Reference: Phys. Rev. Lett. 121, 096803 (2018)] 
Friday, March 8, 2019 10:12AM  10:24AM 
X03.00012: Zeroenergy Andreev bound states from quantum dots in proximitized Rashba nanowires Christopher Reeg, Olesia Dmytruk, Denis Chevallier, Daniel Loss, Jelena Klinovaja We study an analytical model of a Rashba nanowire that is partially covered by and coupled to a thin superconducting layer, where the uncovered region of the nanowire forms a quantum dot. We find that, even if there is no topological phase possible, there is a trivial Andreev bound state that becomes pinned exponentially close to zero energy as a function of magnetic field strength when the length of the dot is tuned with respect to its spinorbit length such that a resonance condition of FabryPerot type is satisfied. In this case, we find that the Andreev bound state remains pinned near zero energy for Zeeman energies that exceed the characteristic spacing between Andreev levels but that are smaller than the spinorbit energy of the dot. Importantly, as the pinning of the Andreev bound state depends only on properties of the dot, we conclude that this behavior is unrelated to topological superconductivity. To support our analytical model, we also perform a numerical simulation of a hybrid system that explicitly incorporates a thin superconducting layer, showing that all qualitative features of our analytical model are present in the numerical results. 
Friday, March 8, 2019 10:24AM  10:36AM 
X03.00013: The survival of topological signatures in the presence of average symmetries Yingyi Huang, ChingKai Chiu The robust properties in topological states of matter under the effect of disorders is of great theoretical as well as experimental interests. One focus is on the disorders breaking either spatial symmetry or nonspatial symmetry (e.g., timereversal, particlehole and chiral symmetry) but restoring it on average. In this work, we consider a quasionedimensional topological superconductor in the presence of disorders preserving average timereversal symmetry or mirror symmetry. By calculating the transport signatures of multichain Kitaev and Majorana models, we show that the survival of the edge modes depends on the form of the disorders. 
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