arXiv subjects

Hepeng Yao

Publications and source records attributed to Hepeng Yao.

At least 19 recordsLinked to original sources

arXiv2026

Universal scaling of many-body effects in quantum tunneling

Quantum tunneling is fundamental to diverse phenomena and underpins a wide range of modern technologies. In the study of superconducting quantum computation and high-temperature superconducting materials, tunneling on multi-particle scale is central. Recently, several cold atom experiments successfully simulated the tunneling process in a many-particle ensemble. However, the many-body nature remains largely unexplored. Here, we observe the universal scaling of many-body effects in quantum tunneling process, using a hexagonal-triangular quantum simulator with independent control of barrier, temperature and interaction. In the weak-interaction regime, the critical tunneling coefficient scales parabolically with temperature under various conditions, in contrast to the linear scaling of single-particle tunneling. By further increasing the interactions beyond the mean-field regime, the scaling exponent decreases, consistent with quantum field theory predictions. Our results address the fundamental question of how many-body effects renormalize quantum tunneling, with direct implications for correlated quantum matter and devices.

cond-mat.quant-gas↗

arXiv2026

Observation of anyonic thermodynamics and generalized Pauli principle

Anyons are quasiparticles with quantum statistics interpolating between those of bosons and fermions. Two distinct manifestations of anyonic behaviour have been theoretically established: fractional exchange statistics where particle exchange can produce any phase, and generalized exclusion statistics which extends the Pauli exclusion principle. While anyons exhibiting fractional exchange statistics have been observed in diverse platforms, experimental realizations of generalized exclusion statistics and direct measurements of its thermodynamic signatures have remained elusive. Here, we realize an anyonic thermodynamic ensemble obeying generalized exclusion statistics and detect its anyonic thermodynamics in a one-dimensional strongly interacting quantum gas. To achieve this, we exploit the bijective mapping between dynamical and statistical interactions in one dimension. By tuning interaction strength and temperature over a wide range, we measure the equation of state and identify clear departures from Bose-Einstein and Fermi-Dirac statistics. These deviations are quantitatively captured by generalized exclusion statistics, providing direct evidence for the generalized Pauli principle. Independent probes of other thermodynamic quantities including pressure and the Tan contact further validate this framework. Our results establish a versatile platform for engineering anyonic exclusion statistics and open the door to thermodynamic applications of anyons in quantum technologies.

cond-mat.quant-gas↗

arXiv2026

Two-mode collapse and revival of quantum coherent state in a tilted optical lattice

Collective dynamics is an important out-of-equilibrium feature of quantum coherent states and usually reflects the intrinsic properties of the state. Collapse and revival (CR) dynamics of phase coherence is a well-known example for bosonic coherent states, which is usually induced by applying a quench. Previous studies have shown that the CR frequency is governed solely by interactions, even in the presence of a tilt quench. However, whether such interaction-dominated oscillation is a universal feature remains unknown. In this work, we show that an ensemble of one-dimensional bosons can undergo two-mode CR, with frequencies set by both the interaction and the tilt, particularly when the tilt is weaker than the interaction. The newly discovered tilt mode is enabled by tunneling between lattice sites. When the two modes coexist, the amplitudes of both modes exhibit universal linear scaling for various tilts. These findings clarify the general features of CR dynamics in tilted lattice models and the underlying mechanism, and provide deeper insight into collective dynamics in correlated systems.

cond-mat.quant-gas↗

arXiv2026

The wave nature of a Mott insulator

Quantum phases of matter are routinely identified by coherence features, with interference patterns being one of the most directly observable quantities. In lattices, the superfluid-to-Mott-insulator (SF-MI) transition is commonly viewed as a change from wave-like coherence to particle-like localization: interference peaks are taken as a hallmark of superfluidity, whereas their disappearance is used to diagnose insulating behavior. Here, we challenge this picture for one-dimensional (1D) strongly interacting gases subject to a lattice potential. We realize a gapped Mott insulator through pinning in a shallow lattice and find that pronounced interference peaks persist deep in the insulating regime. Strikingly, the interference becomes stronger as the Mott fraction increases, demonstrating that a certain degree of coherence still exists in the insulator state. Measurements of the one-body correlation function reveal an oscillatory, exponentially decaying coherence pattern across several lattice sites, in quantitative agreement with quantum Monte Carlo (QMC) simulations. Our work shows that interference does not uniquely diagnose superfluidity and it exposes the unexpected wave nature of a 1D Mott insulator.

cond-mat.quant-gas↗

arXiv2025

Leggett's bound and superfluidity in strongly interacting bosons

A density-based superfluid bound called Leggett's bound has been proved to be a good estimator of the superfluid fraction for cold atomic gases in the mean-field regime. Here, we investigate the accuracy of such bound in the strongly interacting regime, where the mean-field approach fails. Combining quantum Monte Carlo, Gross-Pitaevskii equation and field-theory calculations, we demonstrate that the bound serves as a reliable estimator of the superfluid fraction for strongly interacting bosons at 2D-1D dimensional crossover at low temperatures. By further presenting two counterexamples where the bound predicts trivial results, we shed light on the conditions under which the Leggett's bound serves as a good predictor.

cond-mat.quant-gas↗

arXiv2025

Quench spectroscopy for Lieb-Liniger bosons in the presence of harmonic trap

Quench spectroscopy has emerged as a novel and powerful technique for probing the energy spectrum of various quantum phases for quantum systems from out-of-equilibrium dynamics. While its efficacy has been demonstrated in the homogeneous systems theoretically, most experimental setups feature a confining potential, such as a harmonic trap, which complicates the practical implementations. In this work, we experimentally probe the quench spectroscopy for one-dimensional bosons in optical lattices with the presence of a harmonic trap, and comparing our results with the density matrix renormalization group simulation. For the Mott insulator phase, although a gap is still observed, the band signal is broadened along the frequency space and cut at the half Brillouin zone, which can be explained by the nearest-neighbor tunneling excitations under harmonic confinement. Comparing with the superfluid spectrum, we can see a clear distinction between the two phases and find the inverse quench with larger amplitude yields the clearest spectrum. Our work offers pivotal insights into conducting quench spectroscopy effectively in practical systems.

cond-mat.quant-gas↗

arXiv2025

Probing universal phase diagram of dimensional crossover with an atomic quantum simulator

Dimensionality is a fundamental concept in physics, which plays a hidden but crucial role in various domains, including condensed matter physics, relativity and string theory, statistical physics, etc. In quantum physics, reducing dimensionality usually enhances fluctuations and leads to novel properties. Owing to these effects, quantum simulators in which dimensionality can be controlled have emerged as a new area of interest. However, such a platform has only been studied in specific regimes and a universal phase diagram is lacking. Here, we produce an interacting atomic quantum simulator with continuous tunability of anisotropy and temperature, and probe the universal phase diagram of dimensional crossover. At low temperatures, we identify the regimes from quantum three to zero dimensions. By increasing temperature, we observe the non-trivial emergence of a thermal regime situated between the quantum zero and integer dimensions. We show that the quantum-to thermal transition falls into four different universality classes depending on the dimensionality. Surprisingly, we also detect a fifth type where the high-dimensional quantum system can reach the thermal phase by crossing a low-dimensional quantum regime. Our results provide a crucial foundation for understanding the projective condensed matter structures in unconventional dimensions.

cond-mat.quant-gas↗

arXiv2024

Direct measurement of Tan's contact in a one-dimensional Lieb-Liniger gas

The Tan contact has emerged as a pivotal quantity in characterizing many-body quantum systems, bridging microscopic short-range correlations to thermodynamic behavior. It is defined as the weight of universal $1/k^4$ fall off in momentum distribution tails, which can be measured directly in ultracold gases. So far, however, its direct measurement has been hindered in Bose gases due to interactions strongly affecting the expansion dynamics. Here, we present the first direct measurement of the Tan contact in a strongly-correlated Lieb-Liniger gas. Leveraging the one-dimensional geometry of our system, we implement a two-stage expansion scheme, yielding interaction-immune time-of-flight imaging. Our results show excellent agreement with theoretical predictions from quantum Monte Carlo calculations, which also provides independent thermometry of the experiment. By varying atom number, temperature, and interaction strength, we obtain results consistent with the universal scaling law predicted for the trapped Lieb-Liniger model. Our work paves the way for further characterization of the Lieb-Liniger gas across broad interaction regimes and holds promise for extension to other correlated quantum gases in confined geometries.

cond-mat.quant-gas↗

arXiv2024

Finite size analysis for interacting bosons at the 2D-1D Dimensional Crossover

In this work, we extend the analysis of interacting bosons at 2D-1D dimensional crossover for finite size and temperature by using field-theory approach (bosonization) and quantum Monte Carlo simulations. Stemming from the fact that finite size low-dimensional systems are allowed only to have quasi-ordered phase, we consider the self-consistent harmonic approximation to compute the fraction of quasi-condensate and its scaling with the system size. It allows us to understand the important role played by finite size and temperature across the dimensional crossover for deciding the condensate nature. Furthermore, we consider a mean-field approximation to compute the finite size effect on the crossover temperature for both weak and strong interaction. All the physical quantities we discuss here provide essential information for quantum gas at dimensional crossover and are directly detectable in cold atom experiments

cond-mat.quant-gas↗

arXiv2024

Weak Superfluidity in Twisted Optical Potentials

A controlled twist between different underlying lattices allows one to interpolate, under a unified framework, across ordered and (quasi-)disordered matter while drastically changing quantum transport properties. Here, we use quantum Monte Carlo simulations to determine the unique phase diagrams of strongly-correlated ultracold bosons in twisted optical potentials. We show that at commensurate twisting angles, spectral gaps govern the formation of insulating patterns, separated by thin superfluid domains. The latter form weak superfluids, which are very sensitive to thermal fluctuations, but can be stabilized under appropriate parameter control. In contrast, slightly changing the twisting angle to a incommensurate value destroys most spectral gaps, leaving behind a prominent Bose glass phase. Our results are directly applicable to current generation experiments that quantum simulate moiré physics.

cond-mat.quant-gas↗

arXiv2024

Mott transition for a Lieb-Liniger gas in a shallow quasiperiodic potential: Delocalization induced by disorder

Disorder or quasi-disorder is known to favor the localization in many-body Bose systems. Here in contrast, we demonstrate an anomalous delocalization effect induced by incommensurability in quasiperiodic lattices. Loading ultracold atoms in two shallow periodic lattices with equal amplitude and either equal or incommensurate spatial periods, we show the onset of a Mott transition not only in the periodic case but also in the quasiperiodic case. Upon increase of the incommensurate component of the potential we find that the Mott insulator turns into a delocalized superfluid. Our experimental results agree with quantum Monte Carlo calculations, showing anomalous delocalization induced by the interplay between the commensuration and interaction.

cond-mat.quant-gas↗

arXiv2023

Observation of many-body dynamical localization

The quantum kicked rotor is a paradigmatic model system in quantum physics. As a driven quantum system, it is used to study the transition from the classical to the quantum world and to elucidate the emergence of chaos and diffusion. In contrast to its classical counterpart, it features dynamical localization, specifically Anderson localization in momentum space. The interacting many-body kicked rotor is believed to break localization, as recent experiments suggest. Here, we present evidence for many-body dynamical localization for the Lieb-Liniger version of the many-body quantum kicked rotor. After some initial evolution, the momentum distribution of interacting quantum-degenerate bosonic atoms in one-dimensional geometry, kicked hundreds of times by means of a pulsed sinusoidal potential, stops spreading. We quantify the arrested evolution by analysing the energy and the information entropy of the system as the interaction strength is tuned. In the limiting cases of vanishing and strong interactions, the first-order correlation function exhibits a very different decay behavior. Our results shed light on the boundary between the classical, chaotic world and the realm of quantum physics.

quant-ph↗

arXiv2023

Observation of universal dissipative dynamics in strongly correlated quantum gas

Dissipation is unavoidable in quantum systems. It usually induces decoherences and changes quantum correlations. To access the information of strongly correlated quantum matters, one has to overcome or suppress dissipation to extract out the underlying quantum phenomena. However, here we find an opposite effect that dissipation can be utilized as a powerful tool to probe the intrinsic correlations of quantum many-body systems. Applying highly-controllable dissipation in ultracold atomic systems, we observe a universal dissipative dynamics in strongly correlated one-dimensional quantum gases. The total particle number of this system follows a universal stretched-exponential decay, and the stretched exponent measures the anomalous dimension of the spectral function, a critical exponent characterizing strong quantum fluctuations of this system. This method could have broad applications in detecting strongly correlated features, including spin-charge separations and Fermi arcs in quantum materials.

cond-mat.quant-gas↗

arXiv2023

Cooling bosons by dimensional reduction

Cold atomic gases provide a remarkable testbed to study the physics of interacting many-body quantum systems. They have started to play a major role as quantum simulators, given the high degree of control that is possible. A crucial element is given by the necessarily non-zero temperature. However cooling to the required ultralow temperatures or even simply measuring the temperature directly on the system can prove to be very challenging tasks. Here, we implement thermometry on strongly interacting two- and one-dimensional Bose gases with high sensitivity in the nano-Kelvin temperature range. Our method is aided by the fact that the decay of the first-order correlation function is very sensitive to the temperature when interactions are strong. We find that there may be a significant temperature variation when the three-dimensional quantum gas is cut into two-dimensional slices or into one-dimensional tubes. Strikingly, the temperature for the one-dimensional case can be much lower than the initial temperature. Our findings show that this decrease results from the interplay of dimensional reduction and strong interactions.

cond-mat.quant-gas↗

arXiv2023

Experimental Observation of the 2D-1D Dimensional Crossover in Strongly Interacting Ultracold Bosons

Dimensionality plays an essential role in determining the nature and properties of a physical system. For quantum systems the impact of interactions and fluctuations is enhanced in lower dimensions, leading to a great diversity of genuine quantum effects for reduced dimensionality. In most cases, the dimension is fixed to some integer value. Here, we experimentally probe the dimensional crossover from two to one dimension using strongly interacting ultracold bosons in variable lattice potentials and compare the data to ab-initio theory that takes into account non-homogeneous trapping and non-zero temperature. From a precise measurement of the momentum distribution we analyze the characteristic decay of the one-body correlation function in the two dimensionalities and then track how the decay is modified in the crossover. A varying two-slope structure is revealed, reflecting the fact that the particles see their dimensionality as being one or two depending on whether they are probed on short or long distances, respectively. Our observations demonstrate how quantum properties in the strongly-correlated regime evolve in the dimensional crossover as a result of the interplay between dimensionality, interactions, and temperature.

cond-mat.quant-gas↗

arXiv2023

Thermodynamic Phase Diagram of Two-Dimensional Bosons in a Quasicrystal Potential

Quantum simulation of quasicrystals in synthetic bosonic matter now paves the way to the exploration of these intriguing systems in wide parameter ranges. Yet thermal fluctuations in such systems compete with quantum coherence, and significantly affect the zero-temperature quantum phases. Here we determine the thermodynamic phase diagram of interacting bosons in a two-dimensional, homogeneous quasicrystal potential. Our results are found using quantum Monte Carlo simulations. Finite-size scaling is carefully considered and the quantum phases are systematically distinguished from thermal phases. In particular, we demonstrate stabilization of a genuine Bose glass phase against the normal fluid in sizable parameter ranges. Our results for strong interactions are interpreted using a fermionization picture and experimental relevance is discussed.

cond-mat.quant-gas↗

arXiv2023

Strongly-interacting bosons at 2D-1D Dimensional Crossover

We study a two dimensional (2D) system of interacting quantum bosons, subjected to a continuous periodic potential in one direction. The correlation of such system exhibits a dimensional crossover between a canonical 2D behavior with Berezinski-Kosterlitz-Thouless (BKT) properties and a one-dimensional (1D) behavior when the potential is large and splits the system in essentially independent tubes. The later is in the universality class of Tomonaga-Luttinger liquids (TLL). Using a continuous quantum Monte Carlo method, we investigate this dimensional crossover by computing longitudinal and transverse superfluid fraction as well as the superfluid correlation as a function of temperature, interactions and potential. Especially, we find the correlation function evolves from BKT to TLL type, with special intermediate behaviors appearing at the dimensional crossover. We discuss how the consequences of the dimensional crossover can be investigated in cold atomic gases experiments.

cond-mat.quant-gas↗

arXiv2021

A momentum dependent optical lattice induced by artificial gauge potential

We propose an experimentally feasible method to generate a one-dimensional optical lattice potential in an ultracold Bose gas system that depends on the transverse momentum of the atoms. The optical lattice is induced by the artificial gauge potential generated by a periodically driven multi-laser Raman process, which depends on the transverse momentum of the atoms. We study the many-body Bose-Hubbard model in an effective 1D case and show that the superfluid--Mott-insulator transition can be controlled via tuning the transverse momentum of the atomic gas. We examined our prediction via a strong-coupling expansion to an effective 1D Bose-Hubbard model and a quantum Monte Carlo calculation, and discuss possible applications of our system.

cond-mat.quant-gas↗