Physical Review X最新文献

{"title":"Bulk Superconductivity in Pressurized Trilayer Nickelate Pr4Ni3O10 Single Crystals","authors":"Enkang Zhang, Di Peng, Yinghao Zhu, Lixing Chen, Bingkun Cui, Xingya Wang, Wenbin Wang, Qiaoshi Zeng, Jun Zhao","doi":"10.1103/physrevx.15.021008","DOIUrl":"https://doi.org/10.1103/physrevx.15.021008","url":null,"abstract":"The discovery of superconductivity in pressurized bilayer and trilayer nickelates has generated significant interest. However, their superconducting properties are often dependent on sample quality and pressure conditions, complicating the interpretation of the underlying physics. Finding new systems with optimized bulk superconducting properties is therefore important for advancing our understanding of these materials. Unlike cuprates, where trilayer compounds typically exhibit the highest transition temperature (T</a:mi>c</a:mi></a:msub></a:mrow></a:math>), the bilayer nickelate <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mrow><c:msub><c:mrow><c:mi>La</c:mi></c:mrow><c:mrow><c:mn>3</c:mn></c:mrow></c:msub><c:msub><c:mrow><c:mi>Ni</c:mi></c:mrow><c:mrow><c:mn>2</c:mn></c:mrow></c:msub><c:msub><c:mrow><c:mi mathvariant=\"normal\">O</c:mi></c:mrow><c:mrow><c:mn>7</c:mn></c:mrow></c:msub></c:mrow></c:math> has thus far outperformed the trilayer <f:math xmlns:f=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><f:mrow><f:msub><f:mrow><f:mi>La</f:mi></f:mrow><f:mrow><f:mn>4</f:mn></f:mrow></f:msub><f:msub><f:mrow><f:mi>Ni</f:mi></f:mrow><f:mrow><f:mn>3</f:mn></f:mrow></f:msub><f:msub><f:mrow><f:mi mathvariant=\"normal\">O</f:mi></f:mrow><f:mrow><f:mn>1</f:mn><f:mn>0</f:mn></f:mrow></f:msub></f:mrow></f:math> in reported <i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><i:mrow><i:msub><i:mi>T</i:mi><i:mi>c</i:mi></i:msub></i:mrow></i:math>. Whether the trilayer nickelates have achieved the optimal <k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><k:mrow><k:msub><k:mi>T</k:mi><k:mi>c</k:mi></k:msub></k:mrow></k:math> remains unclear, with various scenarios suggesting different possibilities. Here, we report the discovery of bulk superconductivity in pressurized <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><m:mrow><m:msub><m:mrow><m:mi>Pr</m:mi></m:mrow><m:mrow><m:mn>4</m:mn></m:mrow></m:msub><m:msub><m:mrow><m:mi>Ni</m:mi></m:mrow><m:mrow><m:mn>3</m:mn></m:mrow></m:msub><m:msub><m:mrow><m:mi mathvariant=\"normal\">O</m:mi></m:mrow><m:mrow><m:mn>10</m:mn></m:mrow></m:msub></m:mrow></m:math> single crystals, achieving a maximum onset <p:math xmlns:p=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><p:mrow><p:msub><p:mi>T</p:mi><p:mi>c</p:mi></p:msub></p:mrow></p:math> of 40.5 K at 80.1 GPa, significantly exceeding the 30 K observed in <r:math xmlns:r=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><r:mrow><r:msub><r:mrow><r:mi>La</r:mi></r:mrow><r:mrow><r:mn>4</r:mn></r:mrow></r:msub><r:msub><r:mrow><r:mi>Ni</r:mi></r:mrow><r:mrow><r:mn>3</r:mn></r:mrow></r:msub><r:msub><r:mrow><r:mi mathvariant=\"normal\">O</r:mi></r:mrow><r:mrow><r:mn>1</r:mn><r:mn>0</r:mn></r:mrow></r:msub></r:mrow></r:math>. The bulk nature of superconductivity is confirmed by zero resistance and a strong diamagnetic response below <u:math xmlns:u=\"http://www.w3.org/1998/Math/MathML","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"59 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143805718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Synthetic High Angular Momentum Spin Dynamics in a Microwave Oscillator","authors":"Saswata Roy, Alen Senanian, Christopher S. Wang, Owen C. Wetherbee, Luojia Zhang, B. Cole, C. P. Larson, E. Yelton, Kartikeya Arora, Peter L. McMahon, B. L. T. Plourde, Baptiste Royer, Valla Fatemi","doi":"10.1103/physrevx.15.021009","DOIUrl":"https://doi.org/10.1103/physrevx.15.021009","url":null,"abstract":"Spins and oscillators are foundational to much of physics and applied sciences. For quantum information, a spin 1</a:mn>/</a:mo>2</a:mn></a:mrow></a:math> exemplifies the most basic unit, a qubit. High angular momentum spins (HAMSs) and harmonic oscillators provide multilevel manifolds which have the potential for hardware-efficient protected encodings of quantum information and simulation of many-body quantum systems. In this work, we demonstrate a new quantum control protocol that conceptually merges these disparate hardware platforms. Namely, we show how to modify a harmonic oscillator on demand to implement a continuous range of generators to accomplish linear and nonlinear HAMS dynamics. The spinlike dynamics are verified by demonstration of linear spin coherent [SU(2)] rotations, nonlinear spin rotations, and comparison to other manifolds like simply truncated oscillators. Our scheme allows universal control of a spin cat logical qubit encoding with interpretable drive pulses: We use linear operations to accomplish four logical gates and further show that nonlinear spin rotations can complete the logical gate set. Our results show how motion on a closed Hilbert space can be useful for quantum information processing and opens the door to superconducting circuit simulations of higher angular momentum quantum magnetism. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"38 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143805734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tuning the Coherent Interaction of an Electron Qubit and a Nuclear Magnon","authors":"Noah Shofer, Leon Zaporski, Martin Hayhurst Appel, Santanu Manna, Saimon Covre da Silva, Alexander Ghorbal, Urs Haeusler, Armando Rastelli, Claire Le Gall, Michał Gawełczyk, Mete Atatüre, Dorian A. Gangloff","doi":"10.1103/physrevx.15.021004","DOIUrl":"https://doi.org/10.1103/physrevx.15.021004","url":null,"abstract":"A central spin qubit interacting coherently with an ensemble of proximal spins can be used to engineer entangled collective states or a multiqubit register. Making full use of this many-body platform requires tuning the interaction between the central spin and its spin register. GaAs quantum dots offer a model realization of the central spin system where an electron qubit interacts with multiple ensembles of ∼</a:mo>10</a:mn>4</a:mn></a:msup></a:math> nuclear spins. In this work, we demonstrate tuning of the interaction between the electron qubit and the nuclear many-body system in a GaAs quantum dot. The homogeneity of the GaAs system allows us to perform high-precision and isotopically selective nuclear sideband spectroscopy, which reveals the single-nucleus electronic Knight field. Together with time-resolved spectroscopy of the nuclear field, this fully characterizes the electron-nuclear interaction for control. An algorithmic feedback sequence selects the nuclear polarization precisely, which adjusts the electron-nuclear exchange interaction via the electronic <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mrow><c:mi>g</c:mi></c:mrow></c:math>-factor anisotropy. This allows us to tune directly the activation rate of a collective nuclear excitation (magnon) and the coherence time of the electron qubit. Our method is applicable to similar central-spin systems and enables the programmable tuning of coherent interactions in the many-body regime. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"74 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143805733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Confinement Determines Transport of a Reaction-Diffusion Active Matter Front","authors":"Nicolas Lobato-Dauzier, Ananyo Maitra, André Estevez-Torres, Jean-Christophe Galas","doi":"10.1103/physrevx.15.021007","DOIUrl":"https://doi.org/10.1103/physrevx.15.021007","url":null,"abstract":"Couplings between biochemical and mechanical processes have a profound impact on embryonic development. However, studies capable of quantifying these interactions have remained elusive. Here, we investigate a synthetic system where a DNA reaction-diffusion (RD) front is advected by a turbulent flow generated by active matter (AM) flows in a quasi-one-dimensional geometry. Whereas the dynamics of simple RD fronts solely depend on the reaction and diffusion rates, we show that RD-AM front propagation is also influenced by the confinement geometry. We first experimentally dissected the different components of the reaction-diffusion-advection process by knocking out reaction or advection and observe how RD-AM allows for faster transport over large distances, avoiding dilution. We then show how confinement impacts active matter flow: While changes in instantaneous flow velocities are small, correlation times are dramatically increased with decreasing confinement. As a result, RD-AM front speed increases up to eightfold compared to an RD one, in quantitative agreement with a conveyor-belt reaction-diffusion-advection theoretical model. The RD-AM experimental system described here provides a framework for the rational engineering of complex spatiotemporal processes observed in living systems. It will reinforce our understanding of how macro-scale patterns and structures emerge from microscopic components in nonequilibrium systems. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"72 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143797608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sticking without Contact: Elastohydrodynamic Adhesion","authors":"Vincent Bertin, Alexandros Oratis, Jacco H. Snoeijer","doi":"10.1103/physrevx.15.021006","DOIUrl":"https://doi.org/10.1103/physrevx.15.021006","url":null,"abstract":"The adhesion between dry solid surfaces is typically governed by contact forces, involving surface forces and elasticity. For surfaces immersed in a fluid, out-of-contact adhesion arises due to the viscous resistance to the opening of the liquid gap. While the adhesion between dry solids is described by the classical Johnson-Kendall-Roberts (JKR) theory, there is no equivalent framework for the wet adhesion of soft solids. Here, we investigate theoretically the viscous adhesion emerging during the separation of a sphere from an elastic substrate. The suction pressure within the thin viscous film between the solids induces significant elastic displacements. Unexpectedly, the elastic substrate closely follows the motion of the sphere, leading to a sticking without contact. The initial dynamics is described using similarity solutions, resulting in a nonlinear adhesion force that grows in time as F</a:mi>∝</a:mo>t</a:mi>2</a:mn>/</a:mo>3</a:mn></a:mrow></a:msup></a:math>. When elastic displacements become large enough, another similarity solution emerges that leads to a violent snap-off of the adhesive contact through a finite-time singularity. The observed phenomenology bears a strong resemblance with JKR theory and is relevant for a wide range of applications involving viscous adhesion. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"22 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143797609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Superconductivity in Trilayer Nickelate La4Ni3O10 under Pressure","authors":"Mingxin Zhang, Cuiying Pei, Di Peng, Xian Du, Weixiong Hu, Yantao Cao, Qi Wang, Juefei Wu, Yidian Li, Huanyu Liu, Chenhaoping Wen, Jing Song, Yi Zhao, Changhua Li, Weizheng Cao, Shihao Zhu, Qing Zhang, Na Yu, Peihong Cheng, Lili Zhang, Zhiwei Li, Jinkui Zhao, Yulin Chen, Changqing Jin, Hanjie Guo, Congjun Wu, Fan Yang, Qiaoshi Zeng, Shichao Yan, Lexian Yang, Yanpeng Qi","doi":"10.1103/physrevx.15.021005","DOIUrl":"https://doi.org/10.1103/physrevx.15.021005","url":null,"abstract":"Nickelate superconductors have attracted a great deal of attention over the past few decades due to their similar crystal and electronic structures with high-temperature cuprate superconductors. Here, we report superconductivity in a pressurized Ruddlesden-Popper phase single crystal La</a:mi></a:mrow>4</a:mn></a:mrow></a:msub>Ni</a:mi></a:mrow>3</a:mn></a:mrow></a:msub>O</a:mi></a:mrow>10</a:mn></a:mrow></a:msub>(</a:mo>n</a:mi>=</a:mo>3</a:mn>)</a:mo></a:mrow></a:math> and its interplay with the density wave order in the phase diagram. With increasing pressure, the density wave order, as indicated by the anomaly in the resistivity, is progressively suppressed, followed by the emergence of superconductivity around 25 K under the <f:math xmlns:f=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><f:mrow><f:mi>I</f:mi><f:mn>4</f:mn><f:mo>/</f:mo><f:mi>m</f:mi><f:mi>m</f:mi><f:mi>m</f:mi></f:mrow></f:math> space group. The susceptibility measurements confirm bulk superconductivity with a volume fraction exceeding 80%. Moreover, theoretical analysis unveils that antiferromagnetic superexchange interactions can serve as the effective pairing interaction for the emergence of superconductivity in pressurized <h:math xmlns:h=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><h:mrow><h:msub><h:mrow><h:mi>La</h:mi></h:mrow><h:mrow><h:mn>4</h:mn></h:mrow></h:msub><h:msub><h:mrow><h:mi>Ni</h:mi></h:mrow><h:mrow><h:mn>3</h:mn></h:mrow></h:msub><h:msub><h:mrow><h:mi mathvariant=\"normal\">O</h:mi></h:mrow><h:mrow><h:mn>10</h:mn></h:mrow></h:msub></h:mrow></h:math>. Our research provides a new platform for the investigation of the unconventional superconductivity mechanism in Ruddlesden-Popper trilayer perovskite nickelates. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"217 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Passive Environment-Assisted Quantum Communication with GKP States","authors":"Zhaoyou Wang, Liang Jiang","doi":"10.1103/physrevx.15.021003","DOIUrl":"https://doi.org/10.1103/physrevx.15.021003","url":null,"abstract":"Bosonic pure-loss channel, which represents the process of photons decaying into a vacuum environment, has zero quantum capacity when the channel’s transmissivity is less than 50%. Modeled as a beam splitter interaction between the system and its environment, the performance of bosonic pure-loss channel can be enhanced by controlling the environment state. We show that by choosing the ideal Gottesman-Kitaev-Preskill (GKP) states for the system and its environment, perfect transmission of quantum information through a beam splitter is achievable at arbitrarily low transmissivities. Our explicit constructions allow for experimental demonstration of the improved performance of a quantum channel through passive environment assistance, which is potentially useful for quantum transduction where the environment state can be naturally controlled. In practice, it is crucial to consider finite-energy constraints, and high-fidelity quantum communication through a beam splitter remains achievable with GKP states at the few-photon level. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"24 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143775334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revealing the Electron-Spin Fluctuation Coupling by Photoemission in CaKFe4As4","authors":"Peng Li, Yuzhe Wang, Yabin Liu, Jianghao Yao, Zhisheng Zhao, Zhengtai Liu, Dawei Shen, Huiqian Luo, Guanghan Cao, Juan Jiang, Donglai Feng","doi":"10.1103/physrevx.15.021001","DOIUrl":"https://doi.org/10.1103/physrevx.15.021001","url":null,"abstract":"Electron-boson coupling in unconventional superconductors is one of the key parameters in understanding the superconducting pairing symmetry. Here, we report definitive photoemission evidence of electron-spin fluctuation coupling in the iron-based superconductor CaKFe</a:mi></a:mrow>4</a:mn></a:msub>As</a:mi></a:mrow>4</a:mn></a:msub></a:mrow></a:math>, obtained via high-resolution ARPES. Our study identifies a distinct kink structure on the <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>α</c:mi></c:math> band, observable only in the superconducting phase and closely linked with the superconductivity, indicative of strong electron-boson interactions. Notably, this kink structure corresponds to two distinct bosonic modes at 11 meV and 13 meV, aligning with spin resonance modes previously observed in inelastic neutron-scattering experiments. This alignment underscores the significant role of antiferromagnetic fluctuations in the pairing mechanism of this superconductor. Furthermore, the unique momentum-dependent and orbital-selective properties of the coupling revealed by ARPES provide profound insights into the pairing symmetry, suggesting predominantly <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mrow><e:msub><e:mrow><e:mi>s</e:mi></e:mrow><e:mrow><e:mo>±</e:mo></e:mrow></e:msub></e:mrow></e:math>-wave pairing facilitated by spin fluctuations. Our findings not only highlight the pivotal role of spin resonance in the superconductivity of <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><g:mrow><g:msub><g:mrow><g:mi>CaKFe</g:mi></g:mrow><g:mn>4</g:mn></g:msub><g:msub><g:mrow><g:mi>As</g:mi></g:mrow><g:mn>4</g:mn></g:msub></g:mrow></g:math> but also enhance our understanding of the electron-spin fluctuation interactions in unconventional superconductors. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"19 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143757777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ac Stark Spectroscopy of Interactions between Moiré Excitons and Polarons","authors":"B. Evrard, H. S. Adlong, A. A. Ghita, T. Uto, L. Ciorciaro, K. Watanabe, T. Taniguchi, M. Kroner, A. İmamoğlu","doi":"10.1103/physrevx.15.021002","DOIUrl":"https://doi.org/10.1103/physrevx.15.021002","url":null,"abstract":"We use nonlinear pump-probe spectroscopy to study optical excitations in a charge-tunable MoSe</a:mi></a:mrow>2</a:mn></a:msub>/</a:mo>WS</a:mi></a:mrow>2</a:mn></a:msub></a:mrow></a:math> moiré heterostructure. An intense red-detuned laser pulse creates a photonic dressing of the material by introducing a large population of excitons or exciton polarons in a deep moiré potential. By measuring the resulting ac Stark effect with a weak resonant laser pulse, we gain access to the nature and mutual interactions of the elementary optical excitations. At charge neutrality, our measurements reveal that different exciton resonances, associated with confinement of their center-of-mass motion in the moiré potential, have a significant spatial overlap. The resulting short-range interactions manifest themselves as a density-dependent blueshift for same-valley excitons and bound biexciton states for opposite-valley excitons. The attractive polaron resonance that appears upon injection of electrons into the heterostructure shows a contrasting behavior: Here, we observe an electron-density-independent light shift and a clear pump-power-dependent saturation. These features are equivalent to that of an ensemble of independent two-level emitters and indicate a breakdown of the Fermi-polaron picture for optical excitations of electrons subject to a strong moiré potential. Our work establishes an experimental approach to elucidate the elementary optical excitations of semiconductor moiré heterostructures, providing a solid ground for the spectroscopy of correlated electronic and excitonic states in such materials. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"37 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143757990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Emergence of Sound in a Tunable Fermi Fluid","authors":"Songtao Huang, Yunpeng Ji, Thomas Repplinger, Gabriel G. T. Assumpção, Jianyi Chen, Grant L. Schumacher, Franklin J. Vivanco, Hadrien Kurkjian, Nir Navon","doi":"10.1103/physrevx.15.011074","DOIUrl":"https://doi.org/10.1103/physrevx.15.011074","url":null,"abstract":"Landau’s Fermi-liquid (FL) theory has been successful at the phenomenological description of the normal phase of many different Fermi systems. Using a dilute atomic Fermi fluid with tunable interactions, we investigate the microscopic basis of Landau’s theory with a system describable from first principles. We study transport properties of an interacting Fermi gas by measuring its density response to a periodic external perturbation. In an ideal Fermi gas, we measure for the first time the celebrated Lindhard function. As the system is brought from the collisionless to the hydrodynamic regime, we observe the emergence of sound and find that the experimental observations are quantitatively understood with a first-principle transport equation for the FL. When the system is more strongly interacting, we find deviations from such predictions. Finally, we measure the momentum-space shape of the quasiparticle excitations and see how it evolves from the collisionless to the collisional regime. Our study establishes this system as a clean platform for studying Landau’s theory of the FL and paves the way for extending the theory to more exotic conditions, such as nonlinear dynamics and FLs with strong correlations in versatile settings. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"33 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143744802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}