|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Apr 14, 2023
Today's arXivsummary: https://arxiv.org/abs/2304.06076 by Krupnitska & Brenig. Authors show that the finite temperature second harmonic generation (2HG) allows one to probe characteristic features of two fractional quasiparticle types. 2HG susceptibility displays oscillatory spectrum set by the fermionic excitations. #CondMat #StrEl #arXiv_2304_06076
Finite temperature second harmonic generation in Kitaev magnets

We study electric field induced second harmonic generation (2HG) in the Kitaev model. This frustrated magnet hosts a quantum spin-liquid, featuring fractionalization in terms of mobile Majorana fermion and static $\mathbb{Z}_{2}$ flux-vison elementary excitations. We show that finite temperature 2HG allows to probe characteristic features of both fractional quasiparticle types. In the homogeneous flux state at low-temperatures, the 2HG susceptibility displays an oscillatory spectrum, which is set by only the fermionic excitations and is subject to temperature induced Fermi-blocking, generic to all higher harmonic generation (HHG). In the intermediate to high temperature range, intrinsic randomness, which emerges from thermally excited visons leads to drastic changes of the 2HG susceptibility, resulting from resonance decoupling over a wide range of energies. At the flux proliferation crossover, we suggest an interpolation between these two temperature regimes. Our results satisfy previously established symmetries for electric field induced 2HG in Kitaev magnets.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Apr 13, 2023
Today's #arXivsummary: https://arxiv.org/abs/2304.05553 by Chen et. al. Authors predict that under strong interaction conditions, there exist two distinct types of
constrained thermal phases in a 1D Rydberg blockade array. The first arises in the transverse field dominated regime whose energy transport is super-diffusive; the second is stabilized after adding a growing longitudinal field whose energy diffusion is ballistic. #CondMat #StrEl #arXiv_2304_05553
Superdiffusive to Ballistic Transports in Nonintegrable Rydberg Chains

A common wisdom posits that transports of conserved quantities across clean nonintegrable quantum systems at high temperatures are diffusive when probed from the emergent hydrodynamic regime. We show that this empirical paradigm may alter if the strong interaction limit is taken. Using Krylov-typicality and purification matrix-product-state methods, we establish the following observations for the strongly interacting version of the mixed-field Ising chain, a nonintegrable lattice model imitating the experimental Rydberg blockade array. Given the strict projection owing to the infinite density-density repulsion $V$, the chain's energy transport in the presence of a transverse field $g$ is superdiffusive at infinite temperature featured by an anomalous scaling exponent $\frac{3}{4}$, indicating the existence of a novel dynamical universality class. Imposing, in addition, a growing longitudinal field $h$ causes a drastic factorization of the whole Hilbert space into smaller subsectors, evidenced by the spectral parsing of the eigenstate entanglement. Being a consequence of this approximate symmetry, a superdiffusion-to-ballistic transport transition arises at $h\approx g$. Interestingly, all the above results persist for large but finite interactions and temperatures, provided that the strongly interacting condition $g,h\ll k_\textrm{B}T\ll V$ is fulfilled. Our predictions are verifiable by current experimental facilities.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Apr 12, 2023
Today's #arXivsummary: https://arxiv.org/abs/2304.04787 by Zhao, La Nave, & Phillips. Authors find the Hatsugai-Kohmoto model as a stable quartic fixed point via computation of the β−function in the presence of perturbing local interactions. Agreement with Hubbard arises because both models break the Z2 symmetry on a Fermi surface. #CondMat #StrEl #arXiv_2304_04787
Proof of a Stable Fixed Point for Strongly Correlated Electron Matter

We establish the Hatsugai-Kohmoto model as a stable quartic fixed point (distinct from Wilson-Fisher) by computing the $β-$function in the presence of perturbing local interactions. In vicinity of the half-filled doped Mott state, the $β-$function vanishes for all local interactions regardless of their sign. The only flow away from the HK model is through the superconducting channel which lifts the spin degeneracy as does any ordering tendency. The superconducting instability is identical to that established previously\cite{nat1}. A corollary of this work is that Hubbard repulsive interactions flow into the HK stable fixed point in the vicinity of half-filling. Consequently, although the HK model has all-to-all interactions, nothing local destroys it. The consilience with Hubbard arises because both models break the $Z_2$ symmetry on a Fermi surface, the HK model being the simplest to do so. Indeed, the simplicity of the HK model belies its robustness and generality.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Apr 4, 2023
Today's #arXivsummary: https://arxiv.org/abs/2304.00528 by Misawa et. al. Authors study the dynamical spin transport in the Kitaev-Heisenberg model by applying an AC magnetic field to an edge of the system. In the Kitaev QSL phase, spin polarization at the other edge are resonantly induced in specific spin component. Resonance governed by itinerant Majorana fermions with a broad continuum excitation spectrum. #CondMat #StrEl #arXiv_2304_00528
Interedge spin resonance in the Kitaev quantum spin liquid

The Kitaev model offers a platform for quantum spin liquids (QSLs) with fractional excitations, itinerant Majorana fermions and localized fluxes. Since these fractional excitations could be utilized for quantum computing, how to create, observe, and control them through the spin degree of freedom is a central issue. Here, we study dynamical spin transport in a wide range of frequency for the Kitaev-Heisenberg model, by applying an AC magnetic field to an edge of the system. We find that, in the Kitaev QSL phase, spin polarizations at the other edge are resonantly induced in a specific spin component, even though the static spin correlations are vanishingly small. This interedge spin resonance appears around the input frequency over the broad frequency range. Comparing with the dynamical spin correlations, we clarify that the resonance is governed by the itinerant Majorana fermions with a broad continuum excitation spectrum, which can propagate over long distances, although it vanishes for the pure Kitaev model because of accidental degeneracy and requires weak Heisenberg interactions. We also find that the spin polarizations in the other spin components are weakly induced at an almost constant frequency close to the excitation gap of the localized fluxes, irrespective of the input frequency. These results demonstrate that the dynamical spin transport is a powerful probe of the fractional excitations in the Kitaev QSL. Possible experimental realization of the interedge spin resonance is discussed.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Apr 3, 2023
Today's #arXivsummary: https://arxiv.org/abs/2303.17627 by Zhu et. al. Authors show that random, measurement-only circuits which implement the competition of bond and plaquette couplings of the Kitaev honeycomb model give rise to a structured volume-law entangled phase. Defines error thresholds for the color code in the presence of projective error and stochastic syndrome measurements. #CondMat #StrEl #arXiv_2303_17627
Structured volume-law entanglement in an interacting, monitored Majorana spin liquid

Monitored quantum circuits allow for unprecedented dynamical control of many-body entanglement. Here we show that random, measurement-only circuits, implementing the competition of bond and plaquette couplings of the Kitaev honeycomb model, give rise to a structured volume-law entangled phase with subleading $L \ln L$ liquid scaling behavior. This interacting Majorana liquid takes up a highly-symmetric, spherical parameter space within the entanglement phase diagram obtained when varying the relative coupling probabilities. The sphere itself is a critical boundary with quantum Lifshitz scaling separating the volume-law phase from proximate area-law phases, a color code or a toric code. An exception is a set of tricritical, self-dual points exhibiting effective (1+1)d conformal scaling at which the volume-law phase and both area-law phases meet. From a quantum information perspective, our results define error thresholds for the color code in the presence of projective error and stochastic syndrome measurements. We show that an alternative realization of our model circuit can be implemented using unitary gates plus ancillary single-qubit measurements only.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Mar 30, 2023
Today's #arXivsummary: https://arxiv.org/abs/2303.16222 by Chern & Castelnovo. Authors subject generic nearest-neighbor spin model of Kitaev magnets to a sufficiently strong in-plane magnetic field. Topologically trivial and nontrivial parameter regimes coexist under in-plane magnetic fields. Topological phase diagrams of the magnon bands studied. #CondMat #StrEl #arXiv_2303_16222
Topological phase diagrams of in-plane field polarized Kitaev magnets

While the existence of a magnetic field induced quantum spin liquid in Kitaev magnets remains under debate, its topological properties often extend to proximal phases where they can lead to unusual behaviors of both fundamental and applied interests. Subjecting a generic nearest neighbor spin model of Kitaev magnets to a sufficiently strong in-plane magnetic field, we study the resulting polarized phase and the associated magnon excitations. In contrast to the case of an out-of-plane magnetic field where the magnon band topology is enforced by a three-fold symmetry, we find that it is possible for topologically trivial and nontrivial parameter regimes to coexist under in-plane magnetic fields. We map out the topological phase diagrams of the magnon bands, revealing a rich pattern of variation of the Chern number over the parameter space and the field angle. We further compute the magnon thermal Hall conductivity as a weighted summation of Berry curvatures, and discuss experimental implications of our results to planar thermal Hall effects in Kitaev magnets.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Mar 29, 2023
Today's #arXivsummary: https://arxiv.org/abs/2303.15505 by Popov & Tarnopolsky. Authors consider three stacked graphene monolayers with equal consecutive twist angles. In chiral limit when interlayer couplings ignored, four perfect flat bands found. At magic angles, upper and lower bands touch four exactly flat bands at Dirac point in middle of graphene layer. #CondMat #StrEl #arXiv_2303_15505
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Mar 24, 2023
Today's #arXivsummary: https://arxiv.org/abs/2303.12833 by Castro et. al. Authors predict new interacting electronic orders emerging near higher-order Van Hove singularities present in the Chern bands of the Haldane model. Singularities are classified, revealing regimes of ferromagnetism, density-waves, and superconductivity. Repulsive interactions stabilize long-sought PDW state; exotic Chern supermetal possible in which a non-Fermi liquid phase with an anomalous quantum Hall response realized. #CondMat #StrEl #arXiv_2303_12833
Emergence of Chern Supermetal and Pair-Density Wave through Higher-Order Van Hove Singularities in the Haldane-Hubbard Model

While advances in electronic band theory have brought to light new topological systems, understanding the interplay of band topology and electronic interactions remains a frontier question. In this work, we predict new interacting electronic orders emerging near higher-order Van Hove singularities present in the Chern bands of the Haldane model. We classify the nature of such singularities and employ unbiased renormalization group methods that unveil a complex landscape of electronic orders, which include ferromagnetism, density-waves and superconductivity. Importantly, we show that repulsive interactions can stabilize long-sought pair-density wave state and an exotic Chern supermetal, which is a new class of non-Fermi liquid with anomalous quantum Hall response. This framework opens a new path to explore unconventional electronic phases in two-dimensional chiral bands through the interplay of band topology and higher-order Van Hove singularities.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Mar 24, 2023
Today's #arXivsummary: https://arxiv.org/abs/2303.12348 by Peng et. al. Authors perform large-scale DMRG studies of the lightly doped Hubbard model on the honeycomb lattice on long 3 & 4-leg cylinders. Light doping reveals superconducting state w/coexisting quasi-long range SC & charge density wave orders. #CondMat #StrEl #arXiv_2303_12348
Superconductivity in lightly doped Hubbard model on honeycomb lattice

We have performed large-scale density-matrix renormalization group studies of the lightly doped Hubbard model on the honeycomb lattice on long three and four-leg cylinders. We find that the ground state of the system upon lightly doping is consistent with that of a superconducting state with coexisting quasi-long-range superconducting and charge density wave orders. Both the superconducting and charge density wave correlations decay as a power law at long distances with corresponding exponents $K_{sc}<2$ and $K_c<2$. On the contrary, the spin-spin and single-particle correlations decay exponentially, although with relatively long correlation lengths.

arXiv.org
|Ðr⟩⊕|JθΣħμαħ⟩⊗|Hεατħ⟩Mar 21, 2023
Today's #arXivsummary: https://arxiv.org/abs/2303.10212 by Rüegg et. al. Authors formulate a Chern-Simons (CS) theory of the coupled composite electron liquid (CEL) and composite hole liquid (CHL). Effective action of the CS gauge field fluctuations around the saddle-point leads to stable pairing between CEL and CHL. #CondMat #StrEl #arXiv_2303_10212
Pairing of Composite-Electrons and Composite-Holes in $ν_T=1$ Quantum Hall Bilayers

Motivated by recent experimental indications of preformed electron-hole pairs in $ν_T=1$ quantum Hall bilayers at relatively large separation, we formulate a Chern-Simons (CS) theory of the coupled composite electron liquid (CEL) and composite hole liquid (CHL). We show that the effective action of the CS gauge field fluctuations around the saddle-point leads to stable pairing between CEL and CHL. We find that the CEL-CHL pairing theory leads to a dominant $s$-wave channel in contrast to the dominant $p$-wave channel found in the CEL-CEL pairing theory. Moreover, the CEL-CHL pairing is generally stronger than the CEL-CEL pairing across the whole frequency spectrum. Finally, we discuss possible differences between the two pairing mechanisms that may be probed in experiments.

arXiv.org