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https://www.readbyqxmd.com/read/29341740/digital-quantum-simulation-of-minimal-ads-cft
#1
L García-Álvarez, I L Egusquiza, L Lamata, A Del Campo, J Sonner, E Solano
We propose the digital quantum simulation of a minimal AdS/CFT model in controllable quantum platforms. We consider the Sachdev-Ye-Kitaev model describing interacting Majorana fermions with randomly distributed all-to-all couplings, encoding nonlocal fermionic operators onto qubits to efficiently implement their dynamics via digital techniques. Moreover, we also give a method for probing nonequilibrium dynamics and the scrambling of information. Finally, our approach serves as a protocol for reproducing a simplified low-dimensional model of quantum gravity in advanced quantum platforms as trapped ions and superconducting circuits...
July 28, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29341648/thermal-transport-in-the-kitaev-model
#2
Joji Nasu, Junki Yoshitake, Yukitoshi Motome
In conventional insulating magnets, heat is carried by magnons and phonons. In contrast, when the magnets harbor a quantum spin liquid state, emergent quasiparticles from the fractionalization of quantum spins can carry heat. Here, we investigate unconventional thermal transport yielded by such exotic carriers, in both longitudinal and transverse components, for the Kitaev model, whose ground state is exactly shown to be a quantum spin liquid with fractional excitations described as itinerant Majorana fermions and localized Z_{2} fluxes...
September 22, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29323128/majorana-zero-modes-and-long-range-edge-correlation-in-interacting-kitaev-chains-analytic-solutions-and-density-matrix-renormalization-group-study
#3
Jian-Jian Miao, Hui-Ke Jin, Fu-Chun Zhang, Yi Zhou
We study Kitaev model in one-dimension with open boundary condition by using exact analytic methods for non-interacting system at zero chemical potential as well as in the symmetric case of Δ = t, and by using density-matrix-renormalization-group method for interacting system with nearest neighbor repulsion interaction. We suggest and examine an edge correlation function of Majorana fermions to characterize the long range order in the topological superconducting states and study the phase diagram of the interating Kitaev chain...
January 11, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29230031/two-dimensional-topological-superconductivity-in-pb-co-si-111
#4
Gerbold C Ménard, Sébastien Guissart, Christophe Brun, Raphaël T Leriche, Mircea Trif, François Debontridder, Dominique Demaille, Dimitri Roditchev, Pascal Simon, Tristan Cren
Just like insulators can present topological phases characterized by Dirac edge states, superconductors can exhibit topological phases characterized by Majorana edge states. In particular, one-dimensional topological superconductors are predicted to host zero-energy Majorana fermions at their extremities. By contrast, two-dimensional superconductors have a one-dimensional boundary which would naturally lead to propagating Majorana edge states characterized by a Dirac-like dispersion. In this paper we present evidences of one-dimensional dispersive in-gap edge states surrounding a two-dimensional topological superconducting domain consisting of a monolayer of Pb covering magnetic Co-Si islands grown on Si(111)...
December 11, 2017: Nature Communications
https://www.readbyqxmd.com/read/29219595/topological-majorana-two-channel-kondo-effect
#5
Zhi-Qiang Bao, Fan Zhang
A one-dimensional time-reversal-invariant topological superconductor hosts a Majorana Kramers pair at each end, where time-reversal symmetry acts as a supersymmetry that flips local fermion parity. We examine the transport anomaly of such a superconductor, floating and tunnel-coupled to normal leads at its two ends. We demonstrate the realization of a topologically protected, channel-symmetric, two-channel Kondo effect without fine-tuning. Whereas the nonlocal teleportation vanishes, a lead present at one end telecontrols the universal transport through the other end...
November 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29219553/quantum-phase-transitions-of-the-majorana-toric-code-in-the-presence-of-finite-cooper-pair-tunneling
#6
Ananda Roy, Barbara M Terhal, Fabian Hassler
The toric code based on Majorana fermions on mesoscopic superconducting islands is a promising candidate for quantum information processing. In the limit of vanishing Cooper-pair tunneling, it has been argued that the phase transition separating the topologically ordered phase of the toric code from the trivial one is in the universality class of the (2+1)D XY model. On the other hand, in the limit of infinitely large Cooper-pair tunneling, the phase transition is in the universality class of the (2+1)D Ising model...
November 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29219538/topological-phase-transitions-in-multicomponent-superconductors
#7
Yuxuan Wang, Liang Fu
We study the phase transition between a trivial and a time-reversal-invariant topological superconductor in a single-band system. By analyzing the interplay of symmetry, topology, and energetics, we show that for a generic normal state band structure, the phase transition occurs via extended intermediate phases in which even- and odd-parity pairing components coexist. For inversion-symmetric systems, the coexistence phase spontaneously breaks time-reversal symmetry. For noncentrosymmetric superconductors, the low-temperature intermediate phase is time-reversal breaking, while the high-temperature phase preserves time-reversal symmetry and has topologically protected line nodes...
November 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29219412/nonlocal-entanglement-of-1d-thermal-states-induced-by-fermion-exchange-statistics
#8
YeJe Park, Jeongmin Shim, S-S B Lee, H-S Sim
When two identical fermions exchange their positions, their wave function gains a phase factor of -1. We show that this distance-independent effect can induce nonlocal entanglement in one-dimensional (1D) electron systems having Majorana fermions at the ends. It occurs in the system bulk and has a nontrivial temperature dependence. In a system having a single Majorana fermion at each end, the nonlocal entanglement has a Bell-state form at zero temperature and decays as the temperature increases, vanishing suddenly at a certain finite temperature...
November 24, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29219357/solvable-sachdev-ye-kitaev-models-in-higher-dimensions-from-diffusion-to-many-body-localization
#9
Shao-Kai Jian, Hong Yao
Many aspects of many-body localization (MBL) transitions remain elusive so far. Here, we propose a higher-dimensional generalization of the Sachdev-Ye-Kitaev (SYK) model and show that it exhibits a MBL transition. The model on a bipartite lattice has N Majorana fermions with SYK interactions on each site of the A sublattice and M free Majorana fermions on each site of the B sublattice, where N and M are large and finite. For r≡M/N<r_{c}=1, it describes a diffusive metal exhibiting maximal chaos. Remarkably, its diffusive constant D vanishes [D∝(r_{c}-r)^{1/2}] as r→r_{c}, implying a dynamical transition to a MBL phase...
November 17, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29170399/polarization-of-the-majorana-quasiparticles-in-the-rashba-chain
#10
Maciej M Maśka, Tadeusz Domański
We demonstrate that the selective equal-spin Andreev reflection (SESAR) spectroscopy can be used in STM experiments to distinguish the zero-energy Majorana quasiparticles from the ordinary fermionic states of the Rashba chain. Such technique, designed for probing the p-wave superconductivity, could be applied to the intersite pairing of equal-spin electrons in the chain of magnetic Fe atoms deposited on the superconducting Pb substrate. Our calculations of the effective pairing amplitude for individual spin components imply the magnetically polarized Andreev conductance, which can be used to 'filter' the Majorana quasiparticles from the ordinary in-gap states, although the pure spin current (i...
November 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29155414/quasiparticles-in-condensed-matter-systems
#11
Peter Woelfle
Quasiparticles are a powerful concept of condensed matter quantum theory. In this review the appearence and the properties of quasiparticles are presented in a unifying perspective. The principles behind the existence of quasiparticle excitations in both quantum disordered and ordered phases of fermionic and bosonic systems are discussed . The lifetime of quasiparticles is considered in particular near a continuous classical or quantum phase transition, when the nature of quasiparticles on both sides of a transition into an ordered state changes...
November 20, 2017: Reports on Progress in Physics
https://www.readbyqxmd.com/read/29062031/effect-of-random-feld-disorder-on-topological-superconductors
#12
Tao Zhou
We study the effect of random field disorder on two dimensional topological superconductors based on the Bogoliubov-de Gennes equations. A phase transition from the phase coherent state to the disordered state is identified numerically. The two phases can be characterized by two different correlation functions. In the phase coherent state, Majorana Fermion states form and may be influenced by the interaction between the vortex and the antivortex. The local density of states is calculated, which may be used to distinguish these two phases...
October 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29051593/creating-single-majorana-type-topological-zero-mode-in-superfluids-of-cold-fermionic-atoms
#13
Xiao-Shan Ye, Yong-Jun Liu, Xiu Yun Zhang, Guoqing Wu
We explore the topological phase, which involves Majorana type topological zero mode fermions (MTZFs) at the edge, using d-wave superfluid with Rashba spin-orbit coupling (SOC) interactions. The self-Hermitian of this MTZF([Formula: see text]) is similar to that of the Majorana fermions (MFs) ([Formula: see text]). We show that, to realize a single MTZF at each edge in superfluid with d-wave pairing in a Majorana type Kramers Doublet (MTKD) state, it is important to lift both the spin and the Dirac Cones degeneracies...
October 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29026126/bielectron-vortices-in-two-dimensional-dirac-semimetals
#14
C A Downing, M E Portnoi
Searching for new states of matter and unusual quasi-particles in emerging materials and especially low-dimensional systems is one of the major trends in contemporary condensed matter physics. Dirac materials, which host quasi-particles which are described by ultrarelativistic Dirac-like equations, are of a significant current interest from both a fundamental and applied physics perspective. Here we show that a pair of two-dimensional massless Dirac-Weyl fermions can form a bound state independently of the sign of the inter-particle interaction potential, as long as this potential decays at large distances faster than Kepler's inverse distance law...
October 12, 2017: Nature Communications
https://www.readbyqxmd.com/read/28950615/survival-probability-in-a-quenched-majorana-chain-with-an-impurity
#15
Atanu Rajak, Tanay Nag
We investigate the dynamics of a one-dimensional p-wave superconductor with next-nearest-neighbor hopping and superconducting interaction derived from a three-spin interacting Ising model in transverse field by mapping to Majorana fermions. The next-nearest-neighbor hopping term leads to a new topological phase containing two zero-energy Majorana modes at each end of an open chain, compared to a nearest-neighbor p-wave superconducting chain. We study the Majorana survival probability (MSP) of a particular Majorana edge state when the initial Hamiltonian (H_{i}) is changed to the quantum critical as well as off-critical final Hamiltonian (H_{f}), which additionally contains an impurity term (H_{imp}) that breaks the time-reversal invariance...
August 2017: Physical Review. E
https://www.readbyqxmd.com/read/28949553/probing-spinon-nodal-structures-in-three-dimensional-kitaev-spin-liquids
#16
Gábor B Halász, Brent Perreault, Natalia B Perkins
We propose that resonant inelastic x-ray scattering (RIXS) is an effective probe of the fractionalized excitations in three-dimensional (3D) Kitaev spin liquids. While the non-spin-conserving RIXS responses are dominated by the gauge-flux excitations and reproduce the inelastic-neutron-scattering response, the spin-conserving (SC) RIXS response picks up the Majorana-fermion excitations and detects whether they are gapless at Weyl points, nodal lines, or Fermi surfaces. As a signature of symmetry fractionalization, the SC RIXS response is suppressed around the Γ point...
September 1, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28949178/edge-quantum-criticality-and-emergent-supersymmetry-in-topological-phases
#17
Zi-Xiang Li, Yi-Fan Jiang, Hong Yao
Proposed as a fundamental symmetry describing our Universe, spacetime supersymmetry (SUSY) has not been discovered yet in nature. Nonetheless, it has been predicted that SUSY may emerge in low-energy physics of quantum materials such as topological superconductors and Weyl semimetals. Here, by performing state-of-the-art sign-problem-free quantum Monte Carlo simulations of an interacting two-dimensional topological superconductor, we show convincing evidence that the N=1 SUSY emerges at its edge quantum critical point (EQCP) while its bulk remains gapped and topologically nontrivial...
September 8, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28925381/cavity-qed-with-hybrid-nanocircuits-from-atomic-like-physics-to-condensed-matter-phenomena
#18
Audrey Cottet, Matthieu C Dartiailh, Matthieu M Desjardins, Tino Cubaynes, Lauriane C Contamin, Matthieu Delbecq, Jérémie J Viennot, Laure E Bruhat, Benoit Douçot, Takis Kontos
Circuit QED techniques have been instrumental in manipulating and probing with exquisite sensitivity the quantum state of superconducting quantum bits coupled to microwave cavities. Recently, it has become possible to fabricate new devices in which the superconducting quantum bits are replaced by hybrid mesoscopic circuits combining nanoconductors and metallic reservoirs. This mesoscopic QED provides a new experimental playground to study the light-matter interaction in electronic circuits. Here, we present the experimental state of the art of mesoscopic QED and its theoretical description...
November 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28852054/tunable-odd-frequency-triplet-pairing-states-and-skyrmion-modes-in-chiral-p-wave-superconductor
#19
Yu-Feng Lou, Lin Wen, Guo-Qiao Zha, Shi-Ping Zhou
Bogliubov-de Gennes equations are solved self-consistently to investigate the properties of bound states in chiral p-wave superconductive disks. It shows that either an s-wave or the mixed d- and s-wave state with odd-frequency and spin-triplet symmetry is induced at the vortex core, depending both on the chirality of the pairing states and on the vortex topology. It is also found that the odd-frequency triplet even parity (OTE) bound state can be manipulated with a local non-magnetic potential. Interestingly, with an appropriate potential amplitude, the zero-energy OTE bound state can be stabilized at a distance from the vortex core and from the local potential...
August 29, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28835635/topological-superconductors-from-one-dimensional-periodically-modulated-majorana-chains
#20
Yang Lin, Weichang Hao, Mei Wang, Jianqiang Qian, Huaiming Guo
By analogy to the topological models of fermions in one-dimensional periodically modulated lattices, we provide a systematic method to construct topological superconductors in BDI class. We then create superlattices of Majorana fermions to interpolate several Majorana chains, and realize topological superconductors with arbitrary winding numbers. Two kinds of chiral symmetries are identified in the systems with multiple chains. Of the two winding numbers associated to the chiral symmetries, one counts the number of zero-energy modes, while the other counts the difference of the numbers of α- and β-type Majorana zero states...
August 23, 2017: Scientific Reports
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