Pengcheng Dai
· Sam and Helen Worden Professor, Physics and AstronomyVerifiedRice University · Physics
Active 1989–2026
About
Pengcheng Dai is a professor at Rice University in the Physics Department specializing in experimental condensed matter physics. His research primarily utilizes neutron scattering techniques to investigate strongly correlated electron systems. His work focuses on understanding the microscopic origins of high-transition temperature (T_c) superconductivity, magnetism, and electron-lattice coupling in high-T_c superconductors. Additionally, he studies magnetism and lattice effects in colossal magnetoresistance manganese oxides, as well as quantum criticality in ruthenium-based oxide materials and other transition metal oxides. Dai's research program has been supported by the National Science Foundation and the U.S. Department of Energy for over two decades. Throughout his career, he has made significant contributions to the field, including discoveries related to spin-triplet superconductivity, quantum spin liquid candidates, spin excitation anisotropy, and topological spin excitations in two-dimensional ferromagnets. His work has advanced the understanding of the interplay between magnetism and superconductivity, electron correlations, and spin dynamics in complex materials. In recognition of his sustained research excellence, he was elected as a fellow of the Neutron Scattering Society of America and as a member of the American Academy of Arts and Sciences.
Research topics
- Condensed matter physics
- Quantum mechanics
- Physics
- Mathematics
- Geometry
- Materials science
- Business
- Nanotechnology
Selected publications
Science Advances · 2026-03-06
preprintOpen accessSenior authorCorrespondingIn the search for unconventional magnetism, exotic quantum states are characterized by a lack of order and a broad spin excitation continuum approaching zero temperature. We study the two-dimensional triangular-lattice effective spin- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mn>2</mml:mn> </mml:mfrac> </mml:mrow> </mml:math> system CeMgAl 11 O 19 , which shows slight disorder but no magnetic ordering down to 100 millikelvin. Spin-wave analysis in the magnetic-field–polarized state determines the spin Hamiltonian featuring a mixed ferromagnetic-antiferromagnetic nearest-neighbor exchange interaction [ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>J</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> = −0.024(5) milli–electron volts, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>J</mml:mi> <mml:mo>⊥</mml:mo> </mml:msub> </mml:mrow> </mml:math> = 0.056(3) milli–electron volts]. This places the system near an exactly solvable point of the spin- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mn>2</mml:mn> </mml:mfrac> </mml:mrow> </mml:math> triangular-lattice XXZ model ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>J</mml:mi> <mml:mi>z</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mn>2</mml:mn> </mml:mfrac> <mml:msub> <mml:mi>J</mml:mi> <mml:mo>⊥</mml:mo> </mml:msub> </mml:mrow> </mml:math> ) with extensive ground-state degeneracy. In zero field, neutron spectroscopy reveals a prominent continuum; we show that this arises from an ensemble average of spin-wave spectra across the degenerate ground-state manifold. This demonstrates that the role of weak quenched disorder can be quantitatively constrained: It inhibits unique ground-state selection and stabilizes a local distribution within the degenerate manifold, yielding continuum-like spectra that necessitate a critical reevaluation of the experimental signatures of exotic quantum states.
Physical Review Letters · 2026-01-16
articleOpen accessSpectroscopic measurements in model 1D correlated systems offer insights for understanding their two-dimensional counterparts, which include the cuprate and iron pnictide/chalcogenide superconductors. A major challenge is the identification of such correlated systems with dominantly 1D physics. In this Letter, inelastic neutron scattering measurements on NaFe_{0.53}Cu_{0.47}As single crystal directly reveal quasi-1D spin excitations, resulting from atomic order that leads to magnetic Fe and nonmagnetic Cu chains. The dominant exchange interaction is antiferromagnetic along the chain [SJ_{∥}≈90.1(3) meV], whereas the inter-chain couplings are much weaker [SJ_{⊥}≈-2.4(1) meV and SJ_{c}≈0.15(5) meV]. The quasi-1D spin excitations in NaFe_{0.53}Cu_{0.47}As stem from both the Néel and stripe vectors, with Néel excitations sensitive to Fe impurities on the Cu site. The spin excitations in quasi-1D NaFe_{0.53}Cu_{0.47}As and quasi-2D FeSe exhibit a striking resemblance, suggesting a common origin for their coexistent stripe and Néel excitations. Our findings demonstrate magnetic dilution in NaFeAs leads to dimension reduction of its magnetic degree of freedom, presenting a strategy for discovering low-dimensional quantum materials.
Nano Letters · 2026-02-24
articleOpen accessSenior authorCorrespondingIn two-dimensional (2D) nearly square-lattice quantum materials, electron correlations can induce an electronic nematic phase with 2-fold rotational (C2) symmetry. For 2D materials with 3-fold rotational (C3) symmetry, such as the honeycomb lattice, a vestigial three-state Potts nematic order has been observed in the van der Waals antiferromagnet FePSe3 under uniaxial strain. Here, we use neutron scattering to probe the magnetic order and spin excitations of FePSe3 under uniaxial strain. In the antiferromagnetic (AFM) ordered state, ∼0.6% tensile strain suppresses one zigzag domain and enhances the other two, reducing the AFM order and spin waves to C2 symmetry. This broken C3 symmetry in spin excitations persists slightly above TN ≈ 108.6 K, where zigzag AFM order is absent. These results provide direct evidence of magnetoelastic coupling and suggest that three-state Potts nematicity in paramagnetic spin excitations originates as the vestigial order of the low-temperature zigzag AFM state.
Microscopy · 2026-02-09
articleThe effective mass (m*) and Fermi velocity (vF) are two fundamental gauges of the electronic properties of materials and conventionally measured by magnetotransport characterizations. In this Review, we introduce momentum(q)-resolved electron energy loss spectroscopy (q-EELS) as an alternative method for probing m* and vF, and demonstrate its applications in semiconductor Si and semimetal FeGe. The q-EELS methodology is based on the q-dependent plasmon dispersion in the context of the random-phase approximation (RPA) for a free-electron gas (FEG), featuring a quantitative dependence on m* and vF and thus providing the route for retrieving these parameters. We outline the experimental principles for characterizing plasmon dispersions from the optical light line (the order of 10-3 Å-1) to Brillouin-zone boundaries (the order of Å-1), and elucidate the theoretical framework for pertinent elaborations on m* and vF. This work provides both the conceptual and practical guidelines for employing the q-EELS to extract m* and vF of fundamental significances to electronic characteristics of matters.
Magnetic field-induced momentum-dependent symmetry breaking in a kagome superconductor
Nature Physics · 2026-03-11
articleOpen accessScience Advances · 2026-03-06
articleOpen accessSenior authorCorrespondingIn the search for unconventional magnetism, exotic quantum states are characterized by a lack of order and a broad spin excitation continuum approaching zero temperature. We study the two-dimensional triangular-lattice effective spin-[Formula: see text] system CeMgAl<sub>11</sub>O<sub>19</sub>, which shows slight disorder but no magnetic ordering down to 100 millikelvin. Spin-wave analysis in the magnetic-field-polarized state determines the spin Hamiltonian featuring a mixed ferromagnetic-antiferromagnetic nearest-neighbor exchange interaction [[Formula: see text] = -0.024(5) milli-electron volts, [Formula: see text] = 0.056(3) milli-electron volts]. This places the system near an exactly solvable point of the spin-[Formula: see text] triangular-lattice <i>XXZ</i> model ([Formula: see text]) with extensive ground-state degeneracy. In zero field, neutron spectroscopy reveals a prominent continuum; we show that this arises from an ensemble average of spin-wave spectra across the degenerate ground-state manifold. This demonstrates that the role of weak quenched disorder can be quantitatively constrained: It inhibits unique ground-state selection and stabilizes a local distribution within the degenerate manifold, yielding continuum-like spectra that necessitate a critical reevaluation of the experimental signatures of exotic quantum states.
Physical review. B./Physical review. B · 2026-02-11
articleOpen accessQuantum materials with bands of narrow bandwidth near the Fermi level represent a promising platform for exploring a diverse range of fascinating physical phenomena, as the high density of states within the small energy window often enables the emergence of many-body physics. On one hand, flat bands can arise from strong Coulomb interactions that localize atomic orbitals. On the other hand, quantum destructive interference can quench the electronic kinetic energy. Although both have a narrow bandwidth, the two types of flat bands should exhibit very distinct spectral properties arising from their distinctive origins. So far, the two types of flat bands have only been realized in very different material settings and chemical environments, preventing a direct comparison. Here, we report the observation of the two types of flat bands within the same material system--an above-room-temperature van der Waals ferromagnet, Fe$_{5-x}$GeTe$_2$, distinguishable by a switchable iron site order. The contrasting nature of the flat bands is also identified by the remarkably distinctive temperature-evolution of the spectral features, indicating that one arises from electron correlations in the Fe(1) site-disordered phase, while the other geometrical frustration in the Fe(1) site-ordered phase. Our results therefore provide a direct juxtaposition of the distinct formation mechanism of flat bands in quantum materials, and an avenue for understanding the distinctive roles flat bands play in the presence of magnetism, topology, and lattice geometrical frustration, utilizing sublattice ordering as a key control parameter.
Nano Letters · 2026-02-24
articleSenior authorCorresponding≈ 108.6 K, where zigzag AFM order is absent. These results provide direct evidence of magnetoelastic coupling and suggest that three-state Potts nematicity in paramagnetic spin excitations originates as the vestigial order of the low-temperature zigzag AFM state.
Algorithms · 2026-03-17
articleOpen accessEngineering drawings are fundamental to industries such as oil and gas, construction, and manufacturing. However, current practices relying on manual design or rigid parametric templates often suffer from inefficiency and layout inconsistencies. To address these issues, the layout task is formulated as the Orthogonal Rectangle Packing Problem with Multiple Configurations and Complex Constraints (ORPPMC). The Deep Reinforcement Learning for Multi-Configuration Drawing Layout (DRL-MCDL) framework is proposed, which integrates the Pointer Network for Drawing Element Sequencing (PN-DES) with the Target-Type-Matching-based Multi-Pattern Positioning Strategy (TTM-MPPS). Within this framework, PN-DES employs deep reinforcement learning and feature fusion to combine element attributes with layout configurations for optimal sequence inference, while TTM-MPPS performs precise positioning in accordance with industrial rules to ensure strict adherence to aesthetic requirements. Ablation experiments validate the contribution of each module. Experimental results on real-world engineering drawings demonstrate that DRL-MCDL achieves a Feasibility Rate (FR) exceeding 98.5% on standard instances (12–40 elements), significantly outperforming traditional methods. Furthermore, it maintains a high inference efficiency with an Average Time (AT) of less than 0.3 s, striking an optimal balance between layout quality and computational speed.
Nature Physics · 2025-06-19 · 5 citations
articleSenior authorCorresponding
Recent grants
NSF · $353k · 2008–2011
Magnetic Correlations Through Metal-Insulator Transition in Strongly Correlated Electron Materials
NSF · $330k · 2005–2009
Neutron scattering studies of spin dynamics in iron-based high-temperature superconductors
NSF · $542k · 2017–2021
NSF · $635k · 2021–2025
Neutron scattering studies of spin dynamics in iron-based high-temperature superconductors
NSF · $436k · 2014–2017
Frequent coauthors
- 380 shared
Shiliang Li
- 244 shared
Huiqian Luo
- 228 shared
Xingye Lu
Beijing Normal University
- 201 shared
Meng Wang
Sun Yat-sen University
- 201 shared
J. W. Lynn
- 162 shared
Jiangping Hu
University of Chinese Academy of Sciences
- 150 shared
Yu Song
- 137 shared
Chenglin Zhang
PetroChina Southwest Oil and Gas Field Company (China)
Labs
Condensed matter physics using neutrons to study strongly correlated electron systems, high-Tc superconductivity, magnetism, and electron-lattice coupling.
Education
- 1993
Ph. D, Department of Physics and Astronomy
University of Missouri
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