Layered oxyselenides are of interest as promising mid- to high-temperature thermoelectric applications due to their tunable electrical properties and intrinsically low lattice thermal conductivity (κ). Understanding microscopic phonon mechanisms driving low-κ in these materials is essential for rational design. Here, we report a layer-differentiated phonon transport in Na2CoSe2O via solving the Wigner transport equation based on first-principles calculations, where CoSe6 and Na6O octahedra dominate acoustic and low-energy optical phonons, respectively, together inducing acoustic-optical bunching (a typical feature in homo-layered structures such as bilayer graphene and MoS2). In addition, Na6O generates high-energy flat optical phonons, in contrast to oxide-typical dispersive modes. This phonon dispersion feature, constrained by three-phonon scattering channels, necessitates interpretation via four-phonon processes, which simultaneously enhance wavelike coherent tunneling effects. Consequently, by considering anharmonic phonon renormalization, strong scattering of heat-carrying bunched phonons reduces κ by ~28%, with ~13% compensatory contribution from phonon coherence, yielding a low lattice thermal conductivity of 1.52 W m−1 K−1 at 300 K in Na2CoSe2O. This work provides new insights into the specific vibrational mechanisms, phonon bunching induced strong four-phonon scattering, highlights the critical role of distinct structural layers in governing thermal transport, and enriches the fundamental thermal transport mechanism in layered oxyselenides.
层状氧化硒化物由于其可调谐的电性能和固有的低晶格导热系数（κ）而被认为是有前途的中高温热电应用。了解这些材料中驱动低κ的微观声子机制对于合理设计至关重要。在这里，我们通过求解基于第一性原理计算的Wigner输运方程，报道了Na2CoSe2O中分层声子输运，其中CoSe6和na60八面体分别主导声子和低能光学声子，共同诱导声光聚束（双层石墨烯和MoS2等同质层结构的典型特征）。此外，与典型的氧化物色散模式相比，na60o产生高能量的平面光学声子。这种声子色散特征受到三声子散射通道的限制，需要通过四声子过程来解释，这同时增强了波状相干隧穿效应。因此，通过考虑非谐波声子重整化，携带热量的束状声子的强散射使κ降低了28%，声子相干性补偿了13%，从而在Na2CoSe2O中获得了300 K时1.52 W m−1 K−1的低晶格导热系数。本研究对声子聚集引起的强四声子散射的具体振动机制提供了新的见解，突出了不同结构层在控制热输运中的关键作用，丰富了层状硒化氧化物质的基本热输运机制。
{"title":"Phonon bunching induced strong four-phonon scattering for low lattice thermal conductivity in layered Na2CoSe2O","authors":"Bin Wei, Mengfan Chai, Chang Liu, Junyan Liu, Yongheng Li, Wenyu Zhang, Qing Wang, Erzhen Mu, Binbin Wang, Zhifang Zhou, Changpeng Lin, Xu Chen, Meihua Hu, Yunpeng Zheng, Yuan-Hua Lin","doi":"10.1038/s41535-025-00832-w","DOIUrl":"https://doi.org/10.1038/s41535-025-00832-w","url":null,"abstract":"Layered oxyselenides are of interest as promising mid- to high-temperature thermoelectric applications due to their tunable electrical properties and intrinsically low lattice thermal conductivity (κ). Understanding microscopic phonon mechanisms driving low-κ in these materials is essential for rational design. Here, we report a layer-differentiated phonon transport in Na2CoSe2O via solving the Wigner transport equation based on first-principles calculations, where CoSe6 and Na6O octahedra dominate acoustic and low-energy optical phonons, respectively, together inducing acoustic-optical bunching (a typical feature in homo-layered structures such as bilayer graphene and MoS2). In addition, Na6O generates high-energy flat optical phonons, in contrast to oxide-typical dispersive modes. This phonon dispersion feature, constrained by three-phonon scattering channels, necessitates interpretation via four-phonon processes, which simultaneously enhance wavelike coherent tunneling effects. Consequently, by considering anharmonic phonon renormalization, strong scattering of heat-carrying bunched phonons reduces κ by ~28%, with ~13% compensatory contribution from phonon coherence, yielding a low lattice thermal conductivity of 1.52 W m−1 K−1 at 300 K in Na2CoSe2O. This work provides new insights into the specific vibrational mechanisms, phonon bunching induced strong four-phonon scattering, highlights the critical role of distinct structural layers in governing thermal transport, and enriches the fundamental thermal transport mechanism in layered oxyselenides.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"42 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145919919","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}
Pub Date : 2026-01-03DOI: 10.1038/s41535-025-00843-7
Ke Wang, Qijin Chen, Rufus Boyack, K. Levin
Pair-density-wave (PDW) states are a long-sought-after phase of quantum materials, with the potential to unravel the mysteries of high-Tc cuprates and other strongly correlated superconductors. Yet, surprisingly, a key signature of stable superconductivity, namely the positivity of the superfluid density, ns(T), has not yet been demonstrated. Here, we address this central issue by calculating ns(T) for a generic model two-dimensional PDW superconductor. We uncover a surprisingly large region of intrinsic instability, associated with negative ns(T), revealing that a significant portion of the parameter space thought to be physical cannot support a pure PDW order. In the remaining stable regime, we predict two striking and observable fingerprints: a small longitudinal superfluid response and an unusual temperature dependence for ns(T). These generally model-independent, as well as experimentally relevant findings suggest that the fragility of the superfluid density poses a significant problem for the formation of stable, finite temperature PDW superconductivity.
{"title":"Anomalous superfluid density in pair-density-wave superconductors","authors":"Ke Wang, Qijin Chen, Rufus Boyack, K. Levin","doi":"10.1038/s41535-025-00843-7","DOIUrl":"https://doi.org/10.1038/s41535-025-00843-7","url":null,"abstract":"Pair-density-wave (PDW) states are a long-sought-after phase of quantum materials, with the potential to unravel the mysteries of high-Tc cuprates and other strongly correlated superconductors. Yet, surprisingly, a key signature of stable superconductivity, namely the positivity of the superfluid density, ns(T), has not yet been demonstrated. Here, we address this central issue by calculating ns(T) for a generic model two-dimensional PDW superconductor. We uncover a surprisingly large region of intrinsic instability, associated with negative ns(T), revealing that a significant portion of the parameter space thought to be physical cannot support a pure PDW order. In the remaining stable regime, we predict two striking and observable fingerprints: a small longitudinal superfluid response and an unusual temperature dependence for ns(T). These generally model-independent, as well as experimentally relevant findings suggest that the fragility of the superfluid density poses a significant problem for the formation of stable, finite temperature PDW superconductivity.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"255 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894227","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}
Pub Date : 2025-12-30DOI: 10.1038/s41535-025-00840-w
Kinga Jasiewicz, Paweł Wójcik, Michał P. Nowak, Michał Zegrodnik
We study the interplay between altermagnetism and unconventional superconductivity for two-dimensional square- and triangular-lattice systems. Our approach is based on an effective single particle Hamiltonian which mimics the alternating spin splitting of the d-wave and i-wave altermagnetic state. By supplementing the model with intersite pairing term we characterize the principal features of the coexistent altermagnetic-superconducting state as well as the possibility of inducing the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. Our calculations show that the subtle interplay between the symmetries of the superconducting and altermagnetic order parameters as well as the shape/size of the Fermi surface lead to various types of anisotropic behaviors of the resultant non-zero momentum pairing, which has not been possible in the originally proposed FFLO state. Moreover, additional pairing symmetries appear leading to multi-component order parameter with singlet-triplet mixing. We discuss our result in the context of possible applications like, e.g., the superconducting diode.
{"title":"Interplay between altermagnetism and superconductivity in two dimensions: intertwined symmetries and singlet-triplet mixing","authors":"Kinga Jasiewicz, Paweł Wójcik, Michał P. Nowak, Michał Zegrodnik","doi":"10.1038/s41535-025-00840-w","DOIUrl":"https://doi.org/10.1038/s41535-025-00840-w","url":null,"abstract":"We study the interplay between altermagnetism and unconventional superconductivity for two-dimensional square- and triangular-lattice systems. Our approach is based on an effective single particle Hamiltonian which mimics the alternating spin splitting of the d-wave and i-wave altermagnetic state. By supplementing the model with intersite pairing term we characterize the principal features of the coexistent altermagnetic-superconducting state as well as the possibility of inducing the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. Our calculations show that the subtle interplay between the symmetries of the superconducting and altermagnetic order parameters as well as the shape/size of the Fermi surface lead to various types of anisotropic behaviors of the resultant non-zero momentum pairing, which has not been possible in the originally proposed FFLO state. Moreover, additional pairing symmetries appear leading to multi-component order parameter with singlet-triplet mixing. We discuss our result in the context of possible applications like, e.g., the superconducting diode.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"29 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894234","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}
Pub Date : 2025-12-26DOI: 10.1038/s41535-025-00838-4
Stephen Zhang, Danrui Ni, Ruyi Ke, Guangming Cheng, Nan Yao, Robert J. Cava
Superconductivity in La4Ni3O10 has been reported to emerge upon suppression of intertwined spin and charge density wave (SDW/CDW) order, suggesting a possible connection to the pairing mechanism. Here we report a systematic investigation of La4 Ni3−xCux O10+δ ((0le xle 0.7)), focusing on the evolution of the SDW/CDW order as a function of chemical substitution. Temperature-dependent resistivity, magnetic susceptibility, and Hall effect measurements reveal a linear suppression of density wave transition temperature Tdw and a concurrent enhancement of hole concentration with increasing Cu content. At higher substitution levels ((x > 0.15)), the transition induced anomaly in the resistivity becomes undetectable while a magnetic signature persists, indicating a partial decoupling of spin and charge components and the possible survival of short-range spin correlations. The absence of superconductivity across the substitution series highlights the importance of additional factors in stabilizing the superconducting state in pressurized La4Ni3O10.
{"title":"Suppression of intertwined density waves in La4Ni3-xCuxO10+δ","authors":"Stephen Zhang, Danrui Ni, Ruyi Ke, Guangming Cheng, Nan Yao, Robert J. Cava","doi":"10.1038/s41535-025-00838-4","DOIUrl":"https://doi.org/10.1038/s41535-025-00838-4","url":null,"abstract":"Superconductivity in La4Ni3O10 has been reported to emerge upon suppression of intertwined spin and charge density wave (SDW/CDW) order, suggesting a possible connection to the pairing mechanism. Here we report a systematic investigation of La4 Ni3−xCux O10+δ ((0le xle 0.7)), focusing on the evolution of the SDW/CDW order as a function of chemical substitution. Temperature-dependent resistivity, magnetic susceptibility, and Hall effect measurements reveal a linear suppression of density wave transition temperature Tdw and a concurrent enhancement of hole concentration with increasing Cu content. At higher substitution levels ((x > 0.15)), the transition induced anomaly in the resistivity becomes undetectable while a magnetic signature persists, indicating a partial decoupling of spin and charge components and the possible survival of short-range spin correlations. The absence of superconductivity across the substitution series highlights the importance of additional factors in stabilizing the superconducting state in pressurized La4Ni3O10.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"28 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894251","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}
Nonvolatile optical manipulation of material properties on demand is a highly sought-after feature in the advancement of future optoelectronic applications. Here, we unravel the nature of the single-laser-pulse induced hidden state in 1T-TaS2 by systematically investigating the electronic structure evolution and the pulse-pair control throughout the reversible transition cycle. Our data indicate a mixed-stacking state involving two similarly low-energy interlayer orders, which is manifested as the charge density wave phase disruption. Furthermore, we elucidate distinct mechanisms underlying the bidirectional transformations — the ultrafast formation of the hidden state is initiated by a coherent phonon which triggers a competition between interlayer stacking orders, while its recovery is governed by the progressive domain evolution. Our work highlights the deterministic role of the competing interlayer orders in the nonvolatile phase transition in 1T-TaS2, establishing all-optical engineering of stacking orders in low-dimensional materials as a viable strategy for achieving desirable nonvolatile electronic devices.
{"title":"Nonvolatile optical control of interlayer stacking order in 1T-TaS2","authors":"Junde Liu, Pei Liu, Liu Yang, Sung-Hoon Lee, Mojun Pan, Famin Chen, Jierui Huang, Bei Jiang, Mingzhe Hu, Yuchong Zhang, Zhaoyang Xie, Gang Wang, Mengxue Guan, Wei Jiang, Huaixin Yang, Jianqi Li, Chenxia Yun, Zhiwei Wang, Sheng Meng, Yugui Yao, Tian Qian, Xun Shi","doi":"10.1038/s41535-025-00836-6","DOIUrl":"https://doi.org/10.1038/s41535-025-00836-6","url":null,"abstract":"Nonvolatile optical manipulation of material properties on demand is a highly sought-after feature in the advancement of future optoelectronic applications. Here, we unravel the nature of the single-laser-pulse induced hidden state in 1T-TaS2 by systematically investigating the electronic structure evolution and the pulse-pair control throughout the reversible transition cycle. Our data indicate a mixed-stacking state involving two similarly low-energy interlayer orders, which is manifested as the charge density wave phase disruption. Furthermore, we elucidate distinct mechanisms underlying the bidirectional transformations — the ultrafast formation of the hidden state is initiated by a coherent phonon which triggers a competition between interlayer stacking orders, while its recovery is governed by the progressive domain evolution. Our work highlights the deterministic role of the competing interlayer orders in the nonvolatile phase transition in 1T-TaS2, establishing all-optical engineering of stacking orders in low-dimensional materials as a viable strategy for achieving desirable nonvolatile electronic devices.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"25 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145808183","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}
Pub Date : 2025-12-17DOI: 10.1038/s41535-025-00839-3
Lingfei Zhang, Takahiro C. Fujita, Masashi Kawasaki
Two-dimensional electrons formed at the heterointerfaces of transition metal oxides have been the focus of intensive studies in condensed matter physics since their discovery at LaAlO3/SrTiO3. In particular, various attempts have been made to integrate magnetic properties with such two-dimensional electrons, aiming at exploring spintronic functions. Here we demonstrate a novel approach to realize the spin-polarized two-dimensional electron system at the LaAlO3/SrTiO3 interface by the proximity effect of emergent magnetic fields from adjacent DyFeO3. We observed an unconventional anomalous Hall effect with a remarkable Hall angle of ~20%, resulting from the combination of high-mobility carriers in LaAlO3/SrTiO3 and the emergent magnetic fields from non-coplanar canted antiferromagnetic spin textures in DyFeO3. These findings demonstrate a viable route toward oxide‑based spintronic functionalities by exploiting proximity‑induced emergent fields in two‑dimensional electron systems.
{"title":"Giant unconventional Hall effect in DyFeO3/LaAlO3/SrTiO3 two-dimensional electron system via proximity-induced emergent field","authors":"Lingfei Zhang, Takahiro C. Fujita, Masashi Kawasaki","doi":"10.1038/s41535-025-00839-3","DOIUrl":"https://doi.org/10.1038/s41535-025-00839-3","url":null,"abstract":"Two-dimensional electrons formed at the heterointerfaces of transition metal oxides have been the focus of intensive studies in condensed matter physics since their discovery at LaAlO3/SrTiO3. In particular, various attempts have been made to integrate magnetic properties with such two-dimensional electrons, aiming at exploring spintronic functions. Here we demonstrate a novel approach to realize the spin-polarized two-dimensional electron system at the LaAlO3/SrTiO3 interface by the proximity effect of emergent magnetic fields from adjacent DyFeO3. We observed an unconventional anomalous Hall effect with a remarkable Hall angle of ~20%, resulting from the combination of high-mobility carriers in LaAlO3/SrTiO3 and the emergent magnetic fields from non-coplanar canted antiferromagnetic spin textures in DyFeO3. These findings demonstrate a viable route toward oxide‑based spintronic functionalities by exploiting proximity‑induced emergent fields in two‑dimensional electron systems.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"9 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145765578","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}
Band convergence has been utilized as an effective strategy to enhance the Seebeck coefficient, typically by improving the energy dependence of carrier density near the Fermi level. In contrast, the energy dependence of carrier mobility, which can also enhance the Seebeck coefficient, has attracted less attention. Here, we show that the Seebeck coefficient can be improved when the additional converging band contributes highly mobile carriers, even if they have minimal impact on carrier density. The high-mobility carriers enhance the net diffusion flux, promoting carrier accumulation and amplifying the Seebeck voltage. This mobility-driven enhancement exhibits a hump-like feature in the Pisarenko plot, which becomes flatter and shifts toward lower carrier concentrations as the bands approach. The transport properties of p-type rhombohedral GeTe, as a potential case, were experimentally examined. This work deepens the understanding of band convergence-induced Seebeck coefficient enhancement in thermoelectric materials.
{"title":"Highly mobile carrier-driven Seebeck coefficient enhancement","authors":"Yu Liu, Min Zhang, Lirong Hu, Ziheng Gao, Tianqi Deng, Chenguang Fu, Tiejun Zhu","doi":"10.1038/s41535-025-00837-5","DOIUrl":"https://doi.org/10.1038/s41535-025-00837-5","url":null,"abstract":"Band convergence has been utilized as an effective strategy to enhance the Seebeck coefficient, typically by improving the energy dependence of carrier density near the Fermi level. In contrast, the energy dependence of carrier mobility, which can also enhance the Seebeck coefficient, has attracted less attention. Here, we show that the Seebeck coefficient can be improved when the additional converging band contributes highly mobile carriers, even if they have minimal impact on carrier density. The high-mobility carriers enhance the net diffusion flux, promoting carrier accumulation and amplifying the Seebeck voltage. This mobility-driven enhancement exhibits a hump-like feature in the Pisarenko plot, which becomes flatter and shifts toward lower carrier concentrations as the bands approach. The transport properties of p-type rhombohedral GeTe, as a potential case, were experimentally examined. This work deepens the understanding of band convergence-induced Seebeck coefficient enhancement in thermoelectric materials.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"167 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145765608","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}
Pub Date : 2025-12-15DOI: 10.1038/s41535-025-00834-8
F. Elson, J. Philippe, G. Simutis, O. K. Forslund, M. Abdel-Hafiez, M. Janoschek, R. Khasanov, D. Das, J. Weissenrieder, D. W. Tam, Y. Sassa, M. Månsson
Superconductivity in TiSe2 emerges when the charge density wave (CDW) order is suppressed under pressure or doping. Recent theoretical and experimental studies suggest that a Lifshitz transition plays a key role in stabilizing the superconducting phase. Here, we present muon spin resonance measurements of pressurized TiSe2, revealing a two-gap superconducting state. Our results indicate that the smaller gap contributes unexpectedly strongly to the total superfluid density. This effect is consistent with an enhanced density of states in a newly formed Fermi surface pocket at the Lifshitz transition. These findings provide microscopic insight into the interplay between CDW suppression, Fermi surface reconstruction, and multi-gap superconductivity in TiSe2, demonstrating how pressure-induced changes in electronic structure can shape superconducting properties in layered materials.
{"title":"Lifshitz-enhanced superfluid density in two-gap superconducting TiSe2","authors":"F. Elson, J. Philippe, G. Simutis, O. K. Forslund, M. Abdel-Hafiez, M. Janoschek, R. Khasanov, D. Das, J. Weissenrieder, D. W. Tam, Y. Sassa, M. Månsson","doi":"10.1038/s41535-025-00834-8","DOIUrl":"https://doi.org/10.1038/s41535-025-00834-8","url":null,"abstract":"Superconductivity in TiSe2 emerges when the charge density wave (CDW) order is suppressed under pressure or doping. Recent theoretical and experimental studies suggest that a Lifshitz transition plays a key role in stabilizing the superconducting phase. Here, we present muon spin resonance measurements of pressurized TiSe2, revealing a two-gap superconducting state. Our results indicate that the smaller gap contributes unexpectedly strongly to the total superfluid density. This effect is consistent with an enhanced density of states in a newly formed Fermi surface pocket at the Lifshitz transition. These findings provide microscopic insight into the interplay between CDW suppression, Fermi surface reconstruction, and multi-gap superconductivity in TiSe2, demonstrating how pressure-induced changes in electronic structure can shape superconducting properties in layered materials.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"158 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759429","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}
Pub Date : 2025-12-04DOI: 10.1038/s41535-025-00833-9
Sabrina J. Li, Guru Khalsa, Jeffrey Z. Kaaret, Nicole A. Benedek
Experiments involving resonant optical excitation of infrared-active phonons in crystals have emerged as a powerful new way to tune materials properties. A puzzling and so far unexplained aspect of some so-called nonlinear phononics experiments is that the observed lifetimes of the optically created metastable phases are sometimes orders of magnitude longer than expected based on the nonlinear phononics mechanism assumed in most works. We use a combination of phenomenological theory and first-principles calculations to demonstrate that strong coupling between different lattice degrees of freedom (strains and Raman-active phonons) can give rise to a long-lived metastable phase recently observed in experiments on perovskite LaAlO 3 [Hortensius et al. npj Quantum Mater . 5 95 (2020)]. We show that the long-timescale oscillatory response in the experimental optical reflectivity data is not due solely to shear strains, as originally suggested, but arises from a “hybrid” mode involving displacements of Raman-active phonons of the same symmetry. Our work suggests that strong coupling between different order parameters can provide a mechanism for long-lived optically created metastable phases and points towards strategies, such as strain engineering, for modifying or increasing the lifetime of light-induced phases in ultrafast optical experiments.
涉及晶体中红外主动声子的共振光学激发的实验已经成为调节材料性质的一种强大的新方法。在一些所谓的非线性声子实验中，一个令人困惑和至今无法解释的方面是，根据大多数工作中假设的非线性声子机制，观察到的光学产生的亚稳相的寿命有时比预期的长几个数量级。我们使用现象学理论和第一原理计算的结合来证明不同晶格自由度（应变和拉曼活跃声子）之间的强耦合可以产生最近在钙钛矿LaAlO 3实验中观察到的长寿命亚稳相[Hortensius et al. npj Quantum Mater]。[5][95]（2020）。我们表明，实验光学反射率数据中的长时间振荡响应并不像最初提出的那样仅仅是由于剪切应变，而是由于涉及相同对称性的拉曼主动声子位移的“混合”模式。我们的研究表明，不同阶参量之间的强耦合可以为长寿命的光学创建亚稳相提供一种机制，并指出了在超快光学实验中修改或增加光诱导相寿命的策略，如应变工程。
{"title":"Understanding long-lived metastable phases in ultrafast optical experiments","authors":"Sabrina J. Li, Guru Khalsa, Jeffrey Z. Kaaret, Nicole A. Benedek","doi":"10.1038/s41535-025-00833-9","DOIUrl":"https://doi.org/10.1038/s41535-025-00833-9","url":null,"abstract":"Experiments involving resonant optical excitation of infrared-active phonons in crystals have emerged as a powerful new way to tune materials properties. A puzzling and so far unexplained aspect of some so-called nonlinear phononics experiments is that the observed lifetimes of the optically created metastable phases are sometimes orders of magnitude longer than expected based on the nonlinear phononics mechanism assumed in most works. We use a combination of phenomenological theory and first-principles calculations to demonstrate that strong coupling between different lattice degrees of freedom (strains and Raman-active phonons) can give rise to a long-lived metastable phase recently observed in experiments on perovskite LaAlO <jats:sub>3</jats:sub> [Hortensius et al. <jats:italic>npj Quantum Mater</jats:italic> . 5 95 (2020)]. We show that the long-timescale oscillatory response in the experimental optical reflectivity data is not due solely to shear strains, as originally suggested, but arises from a “hybrid” mode involving displacements of Raman-active phonons of the same symmetry. Our work suggests that strong coupling between different order parameters can provide a mechanism for long-lived optically created metastable phases and points towards strategies, such as strain engineering, for modifying or increasing the lifetime of light-induced phases in ultrafast optical experiments.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"216 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145664961","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}
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