Publications
115 results found
Kadow W, Jin HK, Knolle J, et al., 2024, Single-hole spectra of Kitaev spin liquids: from dynamical Nagaoka ferromagnetism to spin-hole fractionalization, npj Quantum Materials, Vol: 9
The dynamical response of a quantum spin liquid upon injecting a hole is a pertinent open question. In experiments, the hole spectral function, measured momentum-resolved in angle-resolved photoemission spectroscopy (ARPES) or locally in scanning tunneling microscopy (STM), can be used to identify spin liquid materials. In this study, we employ tensor network methods to simulate the time evolution of a single hole doped into the Kitaev spin-liquid ground state. Focusing on the gapped spin liquid phase, we reveal two fundamentally different scenarios. For ferromagnetic spin couplings, the spin liquid is highly susceptible to hole doping: a Nagaoka ferromagnet forms dynamically around the doped hole, even at weak coupling. By contrast, in the case of antiferromagnetic spin couplings, the hole spectrum demonstrates an intricate interplay between charge, spin, and flux degrees of freedom, best described by a parton mean-field ansatz of fractionalized holons and spinons. Moreover, we find a good agreement of our numerical results to the analytically solvable case of slow holes. Our results demonstrate that dynamical hole spectral functions provide rich information on the structure of fractionalized quantum spin liquids.
Wang Z, Wang F, Vovrosh J, et al., 2024, Quantum simulation of hadronic states with Rydberg-dressed atoms, Physical Review A, Vol: 109, ISSN: 2469-9926
The phenomenon of confinement is well known in high-energy physics and can also be realized for low-energy domain-wall excitations in one-dimensional quantum spin chains. A bound state consisting of two domain walls can behave like a meson, and recently, Vovrosh et al. [PRX Quantum 3, 040309 (2022)2691-339910.1103/PRXQuantum.3.040309] demonstrated that a pair of mesons could dynamically form a metastable confinement-induced bound state (consisting of four domain walls) akin to a hadronic state. However, the protocol discussed by Vovrosh et al. involving the use of interactions with characteristically nonmonotonic distance dependence is not easy to come by in nature, thus posing a challenge for its experimental realization. In this regard, Rydberg atoms can provide the required platform for simulating confinement-related physics. We exploit the flexibility offered by interacting Rydberg-dressed atoms to engineering modified spin-spin interactions for the one-dimensional transverse-field Ising model. Our numerical simulations show how Rydberg-dressed interactions can give rise to a variety of effective potentials that are suitable for hadron formation, which opens the possibility of simulating confinement physics with Rydberg platforms as a viable alternative to current trapped-ion experiments.
D'Ornellas P, Knolle J, 2024, Kitaev-Heisenberg model on the star lattice: From chiral Majorana fermions to chiral triplons, Physical Review B, Vol: 109, ISSN: 2469-9950
The interplay of frustrated interactions and lattice geometry can lead to a variety of exotic quantum phases. Here we unearth a particularly rich phase diagram of the Kitaev-Heisenberg model on the star lattice, a triangle decorated honeycomb lattice breaking sublattice symmetry. In the antiferromagnetic regime, the interplay of Heisenberg coupling and geometric frustration leads to the formation of valence bond solid (VBS) phases - a singlet VBS and a bond selective triplet VBS stabilized by the Kitaev exchange. We show that the ratio of the Kitaev versus Heisenberg exchange tunes between these VBS phases and chiral quantum spin-liquid regimes. Remarkably, the VBS phases host a whole variety of chiral triplon excitations with high Chern numbers in the presence of a weak magnetic field. We discuss our results in light of a recently synthesized star lattice material and other decorated lattice systems.
Leeb V, Knolle J, 2024, Interband scattering- and nematicity-induced quantum oscillation frequency in FeSe, Physical Review B, Vol: 109, ISSN: 2469-9950
Understanding the nematic phase observed in the iron-chalcogenide materials is crucial for describing their superconducting pairing. Experiments on FeSe1-xSx showed that one of the slow Shubnikov-de Haas quantum oscillation frequencies disappears when tuning the material out of the nematic phase via chemical substitution or pressure, which has been interpreted as a Lifshitz transition [Coldea et al., npj Quantum Mater. 4, 2 (2019)2397-464810.1038/s41535-018-0141-0; Reiss et al., Nat. Phys. 16, 89 (2020)1745-247310.1038/s41567-019-0694-2]. Here, we present a generic, alternative scenario for a nematicity-induced sharp quantum oscillation frequency, which disappears in the tetragonal phase and is not connected to an underlying Fermi surface pocket. We show that different microscopic interband scattering mechanisms - for example, orbital-selective scattering - in conjunction with nematic order can give rise to this quantum oscillation frequency beyond the standard Onsager relation. We discuss implications for iron-chalcogenides and the interpretation of quantum oscillations in other correlated materials.
Habel J, Mook A, Willsher J, et al., 2024, Breakdown of chiral edge modes in topological magnon insulators, Physical Review B, Vol: 109, ISSN: 2469-9950
Topological magnon insulators (TMI) are ordered magnets supporting chiral edge magnon excitations. These edge states are envisioned to serve as topologically protected information channels in low-loss magnonic devices. The standard description of TMI is based on linear spin-wave theory (LSWT), which approximates magnons as free noninteracting particles. However, magnon excitations of TMI are genuinely interacting even at zero temperature, calling into question descriptions based on LSWT alone. Here we perform a detailed nonlinear spin-wave analysis to investigate the stability of chiral edge magnons. We identify three general breakdown mechanisms: (1) The edge magnon couples to itself, generating a finite lifetime that can be large enough to lead to a spectral annihilation of the chiral state. (2) The edge magnon hybridizes with the extended bulk magnons and, as a consequence, delocalizes away from the edge. (3) Due to a bulk-magnon mediated edge-to-edge coupling, the chiral magnons at opposite edges hybridize. We argue that, in general, these breakdown mechanisms may invalidate predictions based on LSWT and violate the notion of topological protection. We discuss strategies how the breakdown of chiral edge magnons can be avoided, e.g., via the application of large magnetic fields. Our results highlight a challenge for the realization of chiral edge states in TMI and in other bosonic topological systems without particle number conservation.
Khodaeva UE, Kovrizhin DL, Knolle J, 2024, Quantum simulation of the one-dimensional Fermi-Hubbard model as a Z2 lattice-gauge theory, Physical Review Research, Vol: 6, ISSN: 2643-1564
The Fermi-Hubbard model is one of the central paradigms in the physics of strongly correlated quantum many-body systems. Here we propose a quantum circuit algorithm based on the Z2 lattice gauge theory (LGT) representation of the one-dimensional Fermi-Hubbard model, which is suitable for implementation on current NISQ quantum computers. Within the LGT description there is an extensive number of local conserved quantities commuting with the Hamiltonian. We show how these conservation laws can be used to implement an efficient error-mitigation scheme. The latter is based on a postselection of states for noisy quantum simulators. While the LGT description requires a deeper quantum-circuit compared to a Jordan-Wigner (JW) based approach, remarkably, we find that our error-correction protocol leads to results being on par with a standard JW implementation on noisy quantum simulators.
Cassella G, d'Ornellas P, Hodson T, et al., 2023, An exact chiral amorphous spin liquid., Nat Commun, Vol: 14
Topological insulator phases of non-interacting particles have been generalized from periodic crystals to amorphous lattices, which raises the question whether topologically ordered quantum many-body phases may similarly exist in amorphous systems? Here we construct a soluble chiral amorphous quantum spin liquid by extending the Kitaev honeycomb model to random lattices with fixed coordination number three. The model retains its exact solubility but the presence of plaquettes with an odd number of sides leads to a spontaneous breaking of time reversal symmetry. We unearth a rich phase diagram displaying Abelian as well as a non-Abelian quantum spin liquid phases with a remarkably simple ground state flux pattern. Furthermore, we show that the system undergoes a finite-temperature phase transition to a conducting thermal metal state and discuss possible experimental realisations.
Sim G, Pollmann F, Knolle J, 2023, Microscopic details of two-dimensional spectroscopy of one-dimensional quantum Ising magnets, Physical Review B, Vol: 108, ISSN: 2469-9950
The identification of microscopic systems describing the low-energy properties of correlated materials has been a central goal of spectroscopic measurements. We demonstrate how two-dimensional (2D) nonlinear spectroscopy can be used to distinguish effective spin systems whose linear responses show similar behavior. Motivated by recent experiments on the quasi-1D Ising magnet CoNb2O6, we focus on two proposed systems - the ferromagnetic twisted Kitaev spin chain with bond dependent interactions and the transverse field Ising chain. The dynamical spin structure factor probed in linear response displays similar broad spectra for both systems from their fermionic domain wall excitations. In sharp contrast, the 2D nonlinear spectra of the two systems show clear qualitative differences: those of the twisted Kitaev spin chain contain off-diagonal peaks originating from the bond dependent interactions and transitions between different fermion bands absent in the transverse field Ising chain. We discuss the different signatures of spin fractionalization in integrable and nonintegrable regimes of the systems and their connection to experiments.
Zhao H, Knolle J, Moessner R, 2023, Temporal disorder in spatiotemporal order, Physical Review B, Vol: 108, ISSN: 2469-9950
Time-dependent driving holds the promise of realizing dynamical phenomena absent in static systems. Here, we introduce a correlated random driving protocol to realize a spatiotemporal order that cannot be achieved even by periodic driving, thereby extending the discussion of time translation symmetry breaking to randomly driven systems. We find a combination of temporally disordered micromotion with prethermal stroboscopic spatiotemporal long-range order. This spatiotemporal order remains robust against generic perturbations, with an algebraically long prethermal lifetime where the scaling exponent strongly depends on the symmetry of the perturbation, which we account for analytically.
Natori WMH, Jin HK, Knolle J, 2023, Quantum liquids of the S= 32 Kitaev honeycomb and related Kugel-Khomskii models, Physical Review B, Vol: 108, ISSN: 2469-9950
The S=32 Kitaev honeycomb model (KHM) is unique among the spin-S Kitaev models due to a massive ground-state quasidegeneracy that hampered previous numerical and analytical studies. In a recent work [Jin, Nat. Commun. 13, 3813 (2022)2041-172310.1038/s41467-022-31503-0], we showed how an SO(6) Majorana parton mean-field theory of the S=32 isotropic KHM explains the anomalous features of this Kitaev spin liquid (KSL) in terms of an emergent low-energy Majorana flat band. Away from the isotropic limit, the S=32 KSL generally displays a quadrupolar order with gapped or gapless Majorana excitations, features that were quantitatively confirmed by density-matrix renormalization group simulations. In this paper, we explore the connection between the S=32 KHM with Kugel-Khomskii models and discover exactly soluble examples for the latter. We perform a symmetry analysis for the variational parton mean-field Ansätze in the spin and orbital basis for different quantum liquid phases of the S=32 KHM. Finally, we investigate a proposed time-reversal symmetry-breaking spin liquid induced by [111] single-ion anisotropy and elucidate its topological properties as well as experimental signatures, e.g., an unquantized thermal Hall response.
Leeb V, Knolle J, 2023, Quantum oscillations in a doped Mott insulator beyond Onsager's relation, Physical Review B, Vol: 108, ISSN: 2469-9950
The kinetic energy of electrons in a magnetic field is quenched resulting in a discrete set of highly degenerate Landau levels (LLs) which gives rise to fascinating phenomena such as the de Haas-van Alphen effect (dHvAe) or the integer and fractional quantum Hall effects. The latter is a result of interactions partially lifting the degeneracy within a given LL while inter-LL interactions are usually assumed to be unimportant. Here, we study the LL spectrum of the Hatsugai-Kohmoto model, a Hubbard-like model which is exactly soluble on account of infinite-range interactions. For the doped Mott insulator phase in a magnetic field we find that the degeneracy of LLs is preserved but inter-LL interactions are important leading to a nonmonotonous reconstruction of the spectrum. As a result, strong LL repulsion leads to aperiodic quantum oscillations of the dHvAe in contrast to Onsager's famous relation connecting oscillation frequencies with the Fermi surface areas at zero field. In addition, we find unconventional temperature dependencies of quantum oscillations with interaction-induced effective mass renormalizations. We discuss the general importance of inter-LL interactions for understanding doped Mott insulators in magnetic fields.
Huber N, Leeb V, Bauer A, et al., 2023, Quantum oscillations of the quasiparticle lifetime in a metal, NATURE, ISSN: 0028-0836
Leeb V, Knolle J, 2023, Theory of difference-frequency quantum oscillations, Physical Review B, Vol: 108, ISSN: 2469-9950
Quantum oscillations (QOs) describe the periodic variation of physical observables as a function of inverse magnetic field in metals. The Onsager relation connects the basic QO frequencies with the extremal areas of closed Fermi surface pockets, and the theory of magnetic breakdown explains the observation of sums of QO frequencies at high magnetic fields. Here we develop a quantitative theory of difference-frequency QOs in two- and three-dimensional metals with multiple Fermi pockets with parabolic or linearly dispersing excitations. We show that a nonlinear interband coupling, e.g., in the form of interband impurity scattering, can give rise to otherwise forbidden QO frequencies which can persist to much higher temperatures compared to the basis frequencies. We discuss the experimental implications of our findings for various material candidates, for example multifold fermion systems, like CoSi, and the relation to magneto-intersubband oscillations known for coupled two-dimensional electron gases.
Jin H-K, Knolle J, Knap M, 2023, Fractionalized Prethermalization in a Driven Quantum Spin Liquid, PHYSICAL REVIEW LETTERS, Vol: 130, ISSN: 0031-9007
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- Citations: 1
Jin H-K, Natori WMH, Knolle J, 2023, Twisting the Dirac cones of the SU(4) spin-orbital liquid on the honeycomb lattice, PHYSICAL REVIEW B, Vol: 107, ISSN: 2469-9950
Sim G, Knolle J, Pollmann F, 2023, Nonlinear spectroscopy of bound states in perturbed Ising spin chains, PHYSICAL REVIEW B, Vol: 107, ISSN: 2469-9950
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- Citations: 2
Willsher J, Jin H-K, Knolle J, 2023, Magnetic excitations, phase diagram, and order-by-disorder in the extended triangular-lattice Hubbard model, PHYSICAL REVIEW B, Vol: 107, ISSN: 2469-9950
Pizzi A, Malz D, Nunnenkamp A, et al., 2022, Bridging the gap between classical and quantum many-body information dynamics, PHYSICAL REVIEW B, Vol: 106, ISSN: 2469-9950
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- Citations: 4
Franke O, Calugaru D, Nunnenkamp A, et al., 2022, Thermal spin dynamics of Kitaev magnets: Scattering continua and magnetic field induced phases within a stochastic semiclassical approach, PHYSICAL REVIEW B, Vol: 106, ISSN: 2469-9950
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- Citations: 3
Lang H, Hauke P, Knolle J, et al., 2022, Disorder-free localization with Stark gauge protection, PHYSICAL REVIEW B, Vol: 106, ISSN: 2469-9950
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- Citations: 3
Jin H-K, Pizzi A, Knolle J, 2022, Prethermal nematic order and staircase heating in a driven frustrated Ising magnet with dipolar interactions, PHYSICAL REVIEW B, Vol: 106, ISSN: 2469-9950
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- Citations: 3
Zhao H, Knolle J, Moessner R, et al., 2022, Suppression of Interband Heating for Random Driving, PHYSICAL REVIEW LETTERS, Vol: 129, ISSN: 0031-9007
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- Citations: 1
Willsher J, Liu S-W, Moessner R, et al., 2022, Measurement-induced phase transition in a chaotic classical many-body system, PHYSICAL REVIEW B, Vol: 106, ISSN: 2469-9950
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- Citations: 8
Jin H-K, Natori WMH, Pollmann F, et al., 2022, Unveiling the S=3/2 Kitaev honeycomb spin liquids, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 8
Zhao H, Rudner MS, Moessner R, et al., 2022, Anomalous random multipolar driven insulators, PHYSICAL REVIEW B, Vol: 105, ISSN: 2469-9950
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- Citations: 1
Powalla L, Kiemle J, Koenig EJ, et al., 2022, Berry curvature-induced local spin polarisation in gated graphene/WTe<sub>2</sub> heterostructures, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 1
Halimeh JC, Homeier L, Zhao H, et al., 2022, Enhancing Disorder-Free Localization through Dynamically Emergent Local Symmetries, PRX QUANTUM, Vol: 3
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- Citations: 10
Metavitsiadis A, Natori W, Knolle J, et al., 2022, Optical phonons coupled to a Kitaev spin liquid, PHYSICAL REVIEW B, Vol: 105, ISSN: 2469-9950
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- Citations: 7
Vovrosh J, Zhao H, Knolle J, et al., 2022, Confinement-induced impurity states in spin chains, PHYSICAL REVIEW B, Vol: 105, ISSN: 2469-9950
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- Citations: 2
Zhao H, Smith A, Mintert F, et al., 2021, Orthogonal Quantum Many-Body Scars, PHYSICAL REVIEW LETTERS, Vol: 127, ISSN: 0031-9007
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- Citations: 20
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