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Tunable spin-phonon polarons in a chiral molecular qubit framework
Authors:
Aimei Zhou,
Ruihao Bi,
Zhenghan Zhang,
Luming Yang,
Xudong Tian,
Denan Li,
Yingchao Wang,
Mingshu Tan,
Weibin Ni,
Haozhou Sun,
Jinkun Guo,
Xiaohe Miao,
Xinxing Zhao,
Zhifu Shi,
Wei Tong,
Zhitao Zhang,
Jiandong Feng,
Jin-Hu Dou,
Feng Jin,
Shi Liu,
Mircea Dinca,
Tijana Rajh,
Jian Li,
Wenjie Dou,
Lei Sun
Abstract:
Chiral structures that produce asymmetric spin-phonon coupling can theoretically generate spin-phonon polarons -- quasiparticles exhibiting non-degenerate spin states with phonon displacements. These quasiparticles are speculated to be the origin of chirality-induced spin selectivity and presumably can display exotic dynamic behaviors. However, direct experimental evidence of spin-phonon polarons…
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Chiral structures that produce asymmetric spin-phonon coupling can theoretically generate spin-phonon polarons -- quasiparticles exhibiting non-degenerate spin states with phonon displacements. These quasiparticles are speculated to be the origin of chirality-induced spin selectivity and presumably can display exotic dynamic behaviors. However, direct experimental evidence of spin-phonon polarons has been lacking. Using a chiral molecular qubit framework embedding stable semiquinone-like radicals, we report spin dynamic signatures that indicate the formation of spin-phonon polarons for the first time. Our non-adiabatic model reveals that these quasiparticles introduce an active spin relaxation channel when polaron reorganization energy approaches Zeeman splitting. This new channel manifests itself as anomalous, temperature-independent spin relaxation, which can be suppressed by high magnetic fields or pore-filling solvents (e.g. CH2Cl2, CS2). Such field- and guest-tunable relaxation is unattainable in conventional spin systems. Harnessing this mechanism could boost repetition rates in spin-based quantum information technologies without compromising coherence or quantum sensing performance.
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Submitted 20 January, 2026; v1 submitted 5 June, 2025;
originally announced June 2025.
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Ultralong Room-Temperature Qubit Lifetimes of Covalent Organic Frameworks
Authors:
Zhecheng Sun,
Weibin Ni,
Denan Li,
Xiya Du,
Shi Liu,
Lei Sun
Abstract:
Molecular electron spin qubits offer atomic-level tunability and room-temperature quantum coherence. Their integration into engineered solid-state matrices can enhance performance towards ambient quantum information technologies. Herein, we demonstrate covalent organic frameworks (COFs) as programmable matrices of stable organic radical qubits allowing strategic optimization of spin-phonon and spi…
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Molecular electron spin qubits offer atomic-level tunability and room-temperature quantum coherence. Their integration into engineered solid-state matrices can enhance performance towards ambient quantum information technologies. Herein, we demonstrate covalent organic frameworks (COFs) as programmable matrices of stable organic radical qubits allowing strategic optimization of spin-phonon and spin-spin interactions. Using two classic boronate-ester frameworks, COF-5 and COF-108, to host semiquinone-like radical qubits, we achieve ultralong spin relaxation time (T1 > 300 μs) at 298 K, which outperforms most molecular qubits and rivals inorganic spin defects. The suppression of spin relaxation is attributed to rigid and neutral structures as well as carbon-centered spin distributions that effectively weaken spin-phonon coupling. Employing dynamical decoupling methods to both COFs improves their quantum coherence and enables room-temperature detection of nuclear spins including 1H, 11B, and 13C. Our work establishes COFs as designer quantum materials, opening new avenues for quantum sensing of nuclear spins at room temperature.
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Submitted 3 June, 2025;
originally announced June 2025.
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Emergent phases in a compass chain with multisite interactions
Authors:
Wen-Long You,
Cheng-Jie Zhang,
Weihai Ni,
Ming Gong,
Andrzej M. Oleś
Abstract:
We study a dimerised spin chain with biaxial magnetic interacting ions in the presence of an externally induced three-site interactions out of equilibrium. In the general case, the three-site interactions play a role in renormalizing the effective uniform magnetic field. We find that the existence of zero-energy Majorana modes is intricately related to the sign of Pfaffian of the Bogoliubov-de Gen…
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We study a dimerised spin chain with biaxial magnetic interacting ions in the presence of an externally induced three-site interactions out of equilibrium. In the general case, the three-site interactions play a role in renormalizing the effective uniform magnetic field. We find that the existence of zero-energy Majorana modes is intricately related to the sign of Pfaffian of the Bogoliubov-de Gennes Hamiltonian and the relevant $Z_2$ topological invariant. In contrast, we show that an exotic spin liquid phase can emerge in the compass limit through a Berezinskii-Kosterlitz-Thouless (BKT) quantum phase transition. Such a BKT transition is characterized by a large dynamic exponent $z=4$, and the spin-liquid phase is robust under a uniform magnetic field. We find the relative entropy and the quantum discord can signal the BKT transitions. We also uncover a few differences in deriving the correlation functions for the systems with broken reflection symmetry.
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Submitted 31 May, 2017;
originally announced May 2017.
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Quantum phase transitions of a generalized compass chain with staggered Dzyaloshinskii-Moriya interaction
Authors:
Qing-Qiu Wu,
Wei-Hai Ni,
Wen-Long You
Abstract:
We consider a class of one-dimensional compass models with staggered Dzyaloshinskii-Moriya exchange interactions in an external transverse magnetic field. Based on the exact solution derived from Jordan-Wigner approach, we study the excitation gap, energy spectra, spin correlations and critical properties at phase transitions. We explore mutual effects of the staggered Dzyaloshinskii-Moriya intera…
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We consider a class of one-dimensional compass models with staggered Dzyaloshinskii-Moriya exchange interactions in an external transverse magnetic field. Based on the exact solution derived from Jordan-Wigner approach, we study the excitation gap, energy spectra, spin correlations and critical properties at phase transitions. We explore mutual effects of the staggered Dzyaloshinskii-Moriya interaction and the magnetic field on the energy spectra and the ground-state phase diagram. Thermodynamic quantities including the entropy and the specific heat are discussed, and their universal scalings at low temperature are demonstrated.
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Submitted 30 May, 2017;
originally announced May 2017.
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The application of spectrum standardization method for carbon analysis in coal using laser-induced breakdown spectroscopy
Authors:
Xiongwei Li,
Zhe Wang,
Yangting Fu,
Zheng Li,
Jianming Liu,
Weidou Ni
Abstract:
Measurements of carbon content in coal using laser-induced breakdown spectroscopy (LIBS) is limited by its low measurement precision and accuracy. A spectrum standardization method was proposed to achieve both reproducible and accurate results for the quantitative analysis of carbon content in coal with LIBS. The proposed method utilized the molecular carbon emissions to compensate the diminution…
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Measurements of carbon content in coal using laser-induced breakdown spectroscopy (LIBS) is limited by its low measurement precision and accuracy. A spectrum standardization method was proposed to achieve both reproducible and accurate results for the quantitative analysis of carbon content in coal with LIBS. The proposed method utilized the molecular carbon emissions to compensate the diminution of atomic carbon emission caused by matrix effect. The compensated carbon line intensities were further converted into an assumed standard state with fixed plasma temperature, electron density, and total number density of elemental carbon, which is proportional to its concentration in the coal samples. In addition, in order to obtained better compensation for total carbon number density fluctuations, an iterative algorithm was applied, which is different from our previous standardization calculations. The modified spectrum standardization model was applied to the measurement of carbon content in 24 bituminous coal samples. The results demonstrated that the proposed method had superior performance over the generally applied normalization methods. The average relative standard deviation, the coefficient of determination, the root-mean-square error of prediction, and the average maximum relative error for the modified model were 3.44%, 0.83, 2.71%, and 12.61%, respectively, while the corresponding values for the normalization with segmental spectrum area were 6.00%, 0.75, 3.77%, and 15.40%, respectively, showing an overwhelming improvement.
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Submitted 10 February, 2014;
originally announced February 2014.