Quantum wake dynamics in quantum magnets have recently been inferred from the dynamical spin structure factor, which probes only a restricted class of local perturbations. Here, we show that resonant inelastic x-ray scattering (RIXS) selection rules act as an operator filter on fractionalized excitations, producing distinct quantum wakes in the spin-$\frac{1}{2}$ Heisenberg antiferromagnetic chain. Using explicit real-time evolution of single-spin and spin-conserving bond correlators, we find that the conventional spin response propagates up to the maximum spinon velocity, $v_s=\frac{\pi}{2} J$, whereas the bond channels concentrate their spectral weight into a slower dominant wake with $v\simeq 0.92 J$, while weaker components remain bounded by the full spinon light cone. The corresponding momentum- and frequency-resolved responses map onto experimentally accessible RIXS channels, demonstrating that different spectroscopic perturbations resolve complementary pathways of many-body propagation beyond the neutron-scattering spin structure factor. Their inelastic spectral weights further provide access to quantum Fisher information, while equal-time bond sum rules connect the same spectroscopic channels to the ground-state energy. Because the same correlators can be prepared and measured on quantum hardware, they also define direct, experimentally anchored benchmarks for quantum simulations, particularly in frustrated and higher-dimensional magnets where controlled classical real-time calculations become challenging.
Quantum spin ice (QSI) is a three-dimensional quantum spin liquid where fractionalized spinons interact with emergent photons. The XXZ model on the pyrochlore lattice realizes such a $U(1)$ quantum spin liquid and a number of pyrochlore magnets have been investigated as candidate materials, but the detection of emergent excitations has been a major challenge. The specific heat is expected to show the higher-energy spinon excitations and a lower-energy anomaly at the ring-exchange scale, which sets both the photon bandwidth and the energy of the emergent magnetic monopoles (or visons). In reality, the lower-energy peak is obscured by the nuclear Schottky anomaly in non-Kramers Pr-based systems, while it is not clearly resolved from the spinon contributions in Ce-based dipolar-octupolar systems. In this work, we propose a novel thermodynamic probe of the elusive ring-exchange energy scale. We show that in the presence of a weak perturbation coupled to the transverse component of the pseudospin degrees of freedom, the temperature derivative of an observable conjugate to such a weak perturbing force is highly sensitive to the ring-exchange energy scale. Using this scheme, it is shown that the difference between thermal expansion coefficients along the [100] and [010] directions should show a peak at the ring-exchange energy scale for non-Kramers QSI. Similarly, the temperature derivative of the magnetization, $dM/dT$, of dipolar-octupolar pyrochlores under a weak magnetic field can also detect the same signal. Moreover, the sign of these signatures distinguishes the zero-flux and $\pi$-flux QSI states.
Zhengbang Zhou, Tony An, Yong Baek Kim· 0 citations
Strongly anisotropic non-Kramers rare-earth ions combine giant longitudinal g-factors with a vanishing transverse component imposed by time-reversal symmetry, a combination that makes their spin transitions exquisitely sensitive to the orientation of the applied magnetic field. We show that this sensitivity carries a dual identity: it is simultaneously an overlooked decoherence channel and the basis for a spin-coherence-based angular probe. Using pulsed electron paramagnetic resonance at X-band, we report the first measurements of the quantum coherence of Tb$^{3+}$ in a native-doped CaWO$_4$ crystal (15 ppb) and map the Hahn-echo coherence time $T_2$ as a function of temperature (2 to 10 K) and resonant field ($10^3$ to $10^4$ G). A parameter-free model combining spin-lattice relaxation, instantaneous diffusion and spectral diffusion from all independently quantified impurities overestimates $T_2$ by an order of magnitude at low temperature and wrongly predicts the field dependence of $T_2$, inconsistent with the observed monotonic decrease of $T_2$ with $B_r$. A two-parameter extension, including dynamical angular fluctuations of the crystal axis, reproduces the full dataset across multiple setups and laboratories. Two controlled experiments nominally identical except for different mechanical configuration of the setup establish the mechanical origin of the dominant contribution. The two-parameter extension corresponds to an angular amplitude noise spectral density of overall order 36 n{\deg}/$\sqrt{Hz}$ from global external vibrations (ranging from 10 to 66 n{\deg}/$\sqrt{Hz}$ depending on the exact setup mechanical configuration) estimated at $\sim$ 2.5 kHz plus a temperature-dependent contribution assumed to come from local phonon-driven angular jitter. It identifies and highlights a decoherence pathway of practical relevance to any anisotropic solid-state spin system.
Azimuthal hadronic flow measured in ultra-relativistic ion--ion collisions provides a new means of imaging multipole correlations in the ground state of atomic nuclei. Early interpretations largely relied on a classical-rotor picture, in which the measured mean-square elliptic flow is directly related to an intrinsic quadrupole deformation. Atomic nuclei, however, contain additional many-body correlations generated by the Pauli exclusion principle, collective shape fluctuations and non-collective dynamical processes, whose impact on this correspondence has not yet been elucidated. Here, we resolve this issue through an ab initio analysis of $^{16}$O and $^{20}$Ne based on chiral nuclear interactions, combining the in-medium similarity renormalization group with the quantum-number-projected generator coordinate method. By successively isolating antisymmetrization, collective rotational and vibrational, and non-collective dynamical correlations, we determine, for the first time, how each component contributes to the mean-square quadrupole eccentricity. We uncover an unexpected compensation among these distinct correlation mechanisms: despite sizable individual contributions, the squared effective quadrupole deformation inferred from the elliptic flow remains close to the square intrinsic deformation of the nucleus. This result provides a microscopic explanation for the surprising success of the classical-rotor approximation and establishes a quantitative foundation for interpreting $^{16}$O+$^{16}$O and $^{20}$Ne+$^{20}$Ne collision data recently collected at the Large Hadron Collider.
We present magnetic-field-dependent evolution of magnetization and spin dynamics in the quasi-two-dimensional spin-$1/2$ magnet $\mathrm{Cu_2(OH)_3Br}$, consisting of alternately coupled ferromagnetic Cu1 and antiferromagnetic Cu2 spin chains. Terahertz spectroscopy reveals a pronounced field-direction dependence of the low-energy magnetic excitation spectrum. For magnetic fields applied perpendicular to the spin chains, $B\parallel a$ and $B\parallel c^*$, the spectra undergo abrupt reconstructions at the spin-flop transitions identified independently by high-field magnetization measurements. For $B\parallel b$, by contrast, no spin-flop occurs; instead, the excitation spectrum evolves continuously with field and exhibits a strong terahertz radiation polarization dependence as the ferromagnetic Cu1 subsystem becomes progressively polarized. At higher fields, the complex low-field spectrum is replaced by a reduced set of broad excitations, consistent with a weakening of the coupling between the ferromagnetic and antiferromagnetic chain subsystems. Complementary Raman spectroscopy resolves magnon and spinon excitations alongside several phonon modes and traces the characteristic temperature- and magnetic-field-dependent evolution of the magnetic excitations. The combined spectroscopic and magnetization results map out how a magnetic field reorganizes the coupled ferromagnetic and antiferromagnetic subsystems in $\mathrm{Cu_2(OH)_3Br}$ across field-induced phase transitions.
Quantum interference in cold collisions has been predicted to dominate chemical dynamics at low temperatures. However, experimental observations have been largely confined to light-atom systems due to technical challenges. Here, we report direct observation of scattering oscillations in cold ionizing collisions between metastable krypton and rubidium atoms. By combining laser cooling with velocity-mapped ion imaging, we precisely controlled the collision energy from 15 millikelvin to 8 kelvin and detected the ionization products. Below 1 kelvin, pronounced quantum interference between partial waves emerges as the de Broglie wavelength approaches the interaction range. The angular oscillation period scales as θp∝E−1/3, consistent with a Langevin capture model for van der Waals–dominated collisions. Moreover, interference patterns in the angular distribution–collision temperature spectrum are highly sensitive to the long-range potential shape and reveal subtle shape resonances. These observations were corroborated by theoretical calculations. Our results demonstrate the quantum-classical crossover in heavy-atom systems. This study establishes a versatile platform for studying a wide range of laser-coolable species.
Unknown authors· Science Advances· 0 citations
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