arXiv subjects

Shi-Jie Hu

Publications and source records attributed to Shi-Jie Hu.

5 recordsLinked to original sources

arXiv2026

Spinon Singlet Pairing: Microscopic nature of plaquettes in stripy LDOS

Scanning tunneling microscopy (STM) is a powerful tool for visualizing the local density of states (LDOS) of individual stripes in cuprates. However, the microscopic nature of the observed exotic LDOS patterns and their connection to high-$T_c$ superconductivity remain open questions. Within the framework of the quantum colored string model, we reveal that the ubiquitous $4a_0\times4a_0$ plaquettes originate from either the breaking of local spinon singlet pairs through hole insertion, or the formation of an unpaired spinon upon electron addition in a stripe. Moreover, by comparing our data with LDOS of cuprates, we identify an effect of particle-hole symmetry breaking (PHSB): a $2a_0$ shift, which is predicted and confirmed in a longer stripe ($L=18$). At last, we establish and verify a general relation between hole density and plaquette size across multiple fillings. Our work offers a fresh wavefunction-based perspective on interpreting STM signals in cuprate experiments and demonstrates that their origin may arise from spinon singlet pairing in the ground state of fluctuating stripes, the same mechanism underlying the $d$-wave sign structure [Phys. Rev. Lett. \textbf{137}, 086702 (2026)].

cond-mat.str-el↗

arXiv2026

Spinon Singlet Pairing: Origin of $d$-Wave Sign Structure in a Partially-Filled Stripe

Significant research advances have led to a consensus that the Fermi-Hubbard model and its extended variants are archetypical frameworks for elucidating the intertwined relationship between stripe orders and superconductivity in hole-doped high-$T_c$ materials. Notably, the Hubbard quantum simulator has recently achieved several remarkable breakthroughs, e.g., being cooled down to the cryogenic regime and enabling the observation of stable fluctuating stripes. However, the microscopic mechanism underlying the $d$-wave pairing of electrons in the presence of stripes at low temperatures remains poorly understood due to the intricate interplay between strongly correlated effects and non-negligible thermal fluctuations. Here, we conduct a close investigation of a partially-filled stripe in the representative $t$-$J$ and $t$-$t'$-$U$ models with both numerical and analytical methods. Analogous to quantum gas microscopy, the perfect sampling technique allows us to obtain the high-confidence-level statistics of the Fock basis states appearing in the ground-state wavefunction. In a novel physical paradigm, these data demonstrate that two spinons with opposite chiralities tend to pair spontaneously into a singlet state, thereby naturally giving rise to the $d$-wave pairing pattern. Then, using the updated effective theory of quantum colored string, we have reconstructed the wavefunction and have determined the nature of spinon pairing and its connection to the $d$-wave sign structure of pair-pair correlation. Furthermore, spinon singlet pairs enable the establishment of a long-range pair-pair correlation between the two stripes. Our work offers new insights into the microscopic physics of stripes and paves the way for further exploration of multi-stripe-mediated pairing mechanisms in the Fermi-Hubbard model.

cond-mat.str-el↗

arXiv2025

Quantum colored strings in the hole-doped $t$-$J_z$ model

The stripe phase, an intertwined order observed in high-temperature superconductors, is regarded as playing a key role in elucidating the underlying mechanism of superconductivity, especially in cuprates. Following Jan Zaanen's early scenario, the filled charge stripe, with one hole per unit cell of the charge order, can be taken as the interactive elastic quantum strings of holes, stabilized by $π$-phase shifts between neighboring magnetic domains. However, this scenario is challenging to explain, particularly in terms of electron pairing, which necessitates hole pairs. In this work, we propose a new effective model for describing the stripe phase in the hole-doped $t$-$J_z$ model. With respect to the antiferromagnetic background, the model comprises three types of color-labeled point-defects coupling to an effective spin field, so named as ``colored string". Comparing with numerical results from large-scale density matrix renormalization group (DMRG) simulations, we find semi-quantitative agreement in local hole density, magnetic moment, and the newly proposed spectrum features of the effective spin field. By systematically analyzing the hole-density distribution and the scaling of groundstate energy at different system sizes, we determine the effective core radius and the effective hopping amplitude of the quantum string. Furthermore, the local pinning field can be finely adjusted to drag the quantum string, offering a potential method for detecting it in optical lattices. At last, we further demonstrate the partially-filled stripe with less than one hole per unit cell of the charge order can also be well described by the effective theory.

cond-mat.str-el↗

arXiv2025

Competition between dimerization and vector chirality in the spin-$3/2$ $J_1$-$J_2$ Heisenberg chain with uniaxial single-ion anisotropy

The spin-$3/2$ chain is a versatile prototypical platform for the study of competition between different kinds of magnetic orders, with the objective of obtaining a deeper understanding of the corresponding quantum phase transitions. In this work, we investigate the spin-$3/2$ chain with nearest-neighbor $J_1$, next-nearest-neighbor $J_2$, and uniaxial single-ion anisotropy $D$ terms in the absence of a magnetic field. For positive values of $J_2/J_1$ and $D/J_1$, we find seven different phases in a rich phase diagram. Without frustration $J_2=0$, a gapless Luttinger liquid phase remains stable for all $D>0$. As $J_2$ increases, we observe three phases with distinct dimerized valence bond orders, which show an intricate competition with vector chiral order and incommensurate correlations. For large $J_2$, regions of phase coexistence between the dimerized and vector chiral orders emerge. We present large-scale numerical data for the determination of transition lines, order parameters, and the nature of the phase transitions.

cond-mat.str-el↗

arXiv2024

Spinon Singlet in Quantum Colored String: Origin of $d$-Wave Pairing in a Partially-Filled Stripe

Although both experimental observations and numerical simulations have reached a consensus that the stripe phase is intertwined with superconductivity in cuprates, the microscopic mechanism behind $d$-wave pairing in the presence of stripes remains unclear. Using the effective theory of quantum colored strings, we derive the wavefunction in Fock space. Our results show that two spinons with opposite chiralities tend to pair into a spinon singlet, which in turn facilitates the formation of negative pair-pair correlations between distant $x$-bonds and $y$-bonds, a hallmark of the $d$-wave pairing pattern. The same pair-pair correlation pattern is observed across various models, as confirmed by large-scale density matrix renormalization group calculations. Based on these results, we conclude that the spinon singlet is the origin of $d$-wave superconductivity in a fluctuating, partially-filled stripe, and this mechanism may also extend to multi-stripe configurations.

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