The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Ion Errea - One of the best experts on this subject based on the ideXlab platform.
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weak dimensionality dependence and dominant role of ionic fluctuations in the Charge Density Wave transition of nbse_ 2
Physical Review Letters, 2020Co-Authors: Raffaello Bianco, Lorenzo Monacelli, Matteo Calandra, Francesco Mauri, Ion ErreaAbstract:Contradictory experiments have been reported about the dimensionality effect on the Charge-Density-Wave transition in 2H ${\mathrm{NbSe}}_{2}$. While scanning tunneling experiments on single layers grown by molecular beam epitaxy measure a Charge-Density-Wave transition temperature in the monolayer similar to the bulk, around 33 K, Raman experiments on exfoliated samples observe a large enhancement of the transition temperature up to 145 K. By employing a nonperturbative approach to deal with anharmonicity, we calculate from first principles the temperature dependence of the phonon spectra both for bulk and monolayer. In both cases, the Charge-Density-Wave transition temperature is estimated as the temperature at which the phonon energy of the mode driving the structural instability vanishes. The obtained transition temperature in the bulk is around 59 K, in rather good agreement with experiments, and it is just slightly increased in the single-layer limit to 73 K, showing the weak dependence of the transition on dimensionality. Environmental factors could motivate the disagreement between the transition temperatures reported by experiments. Our analysis also demonstrates the predominance of ionic fluctuations over electronic ones in the melting of the Charge-Density-Wave order.
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Weak Dimensionality Dependence of the Charge Density Wave Transition in NbSe$_2$
arXiv: Mesoscale and Nanoscale Physics, 2020Co-Authors: Raffaello Bianco, Lorenzo Monacelli, Matteo Calandra, Francesco Mauri, Ion ErreaAbstract:Contradictory experiments have been reported about the dimensionality effect on the Charge Density Wave transition in 2H NbSe$_2$. While scanning tunnelling experiments on single layers grown by molecular beam epitaxy measure a Charge Density Wave transition temperature in the monolayer similar to the bulk, around 33 K, Raman experiments on exfoliated samples observe a large enhancement of the transition temperature up to 145 K. By calculating from first principles the Charge Density Wave temperature, we determine that the intrinsic Charge Density Wave is barely affected by dimensionality as suggested by the scanning tunnelling experiments. The transition temperature is estimated by calculating the temperature dependence of the phonon spectra within a non-perturbative approach to deal with anharmonicity and determining at which temperature the phonon energy of the mode driving the instability vanishes. The obtained transition temperature in the bulk is around 59 K, in rather good agreement with experiments, and it is just slightly increased in the single-layer limit to 73 K, showing the weak dependence of the transition on dimensionality. Our results demonstrate that the Charge Density Wave melts due to the ionic contribution to the entropy, not the electronic one, and underline that environmental factors, such as sample preparation or the substrate, have a large impact on the transition temperatures.
Pierre Monceau - One of the best experts on this subject based on the ideXlab platform.
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Features of Pinning of a Charge-Density Wave in Quasi-Two-Dimensional Compounds
JETP Letters, 2019Co-Authors: A. V. Frolov, A. P. Orlov, A. A. Sinchenko, Pierre MonceauAbstract:Effects of the collective motion (sliding) of a Charge Density Wave in the TbTe3 quasi-two-dimensional conductor have been studied in a wide temperature interval. Immediately after cooling to temperatures below the Peierls transition temperature TCDW = 336 K, the threshold field Et of sliding initiation of the Charge Density Wave has a nearly linear temperature dependence. The aging of samples at a fixed temperature T0 < TCDW for several hours significantly modifies the sliding of the Charge Density Wave. The threshold field increases significantly and the temperature dependence of Et becomes nonmonotonic, demonstrating a large maximum at T = T0. The observed effect is attributed to the aging-induced formation of an ordered structure (lattice) of defects of the Charge Density Wave and to change in the pinning regime at the melting of this structure.
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Elastic anomalies at the Charge Density Wave transition in TbTe3
Solid State Communications, 2016Co-Authors: Michel Saint-paul, Christophe Guttin, Pascal Lejay, Gyorgy Remenyi, Olivier Leynaud, Pierre MonceauAbstract:The set of elastic constants of the Charge Density Wave (CDW) rare earth tritelluride TbTe3 has been measured at 15 MHz in the temperature range 300-360 K. Large anomalies in the velocity and ultrasonic attenuation of the longitudinal C11 and C33 modes are observed at the Charge Density Wave phase transition TCDW = 333 K. Anisotropic stress dependence dTCDW/dp is found, the component dTCDW/dp1 and dTCDW/dp3 in the (a,c) plane are one order of magnitude larger than the component dTCDW/dp2 perpendicular to it. The Landau theory has been used to explain the explain the experimental data.Critical behavior near the Charge Density Wave phase transition is described in terms of a phenomenological dynamic scaling theory.
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Elastic anomalies at the Charge Density Wave transition in TbTe3
Solid State Communications, 2016Co-Authors: Michel Saint-paul, Christophe Guttin, Pascal Lejay, Gyorgy Remenyi, Olivier Leynaud, Pierre MonceauAbstract:Abstract The set of elastic constants of the Charge Density Wave (CDW) rare earth tritelluride TbTe3 has been measured at 15 MHz in the temperature range 300–360 K. Large anomalies in the velocity and ultrasonic attenuation of the longitudinal C11 and C33 modes are observed at the Charge Density Wave phase transition TCDW=333 K. Anisotropic stress dependence ∂ T C D W / ∂ σ is found, the components ∂ T C D W / ∂ σ 11 and ∂ T C D W / ∂ σ 33 in the (a,c) plane are one order of magnitude larger than the component ∂ T C D W / ∂ σ 22 perpendicular to it. The Landau theory has been used to explain the experimental data. Critical behaviour near the Charge Density Wave phase transition is described in terms of a phenomenological dynamic scaling theory.
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Sliding Charge-Density Wave in two-dimensional rare-earth tellurides
Physical Review B: Condensed Matter and Materials Physics, 2013Co-Authors: A. A. Sinchenko, Pascal Lejay, Pierre MonceauAbstract:Nonlinear transport properties are reported in the layered DyTe3 compound at a temperature below the Charge-Density-Wave (CDW) transition T-P = 302 K. Conductivity increases sharply above the threshold electric field. Under application of a rf field, Shapiro steps are clearly observed. These features demonstrate CDW sliding in two-dimensional compounds.
B A Bernevig - One of the best experts on this subject based on the ideXlab platform.
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axionic Charge Density Wave in the weyl semimetal tase4 2i
Nature, 2019Co-Authors: Johannes Gooth, Barry Bradlyn, S Honnali, Clemens Philipp Schindler, Neeraj Kumar, Jonathan Noky, C Shekhar, Yan Sun, Zixuan Wang, B A BernevigAbstract:An axion insulator is a correlated topological phase, which is predicted to arise from the formation of a Charge-Density Wave in a Weyl semimetal1,2—that is, a material in which electrons behave as massless chiral fermions. The accompanying sliding mode in the Charge-Density-Wave phase—the phason—is an axion3,4 and is expected to cause anomalous magnetoelectric transport effects. However, this axionic Charge-Density Wave has not yet been experimentally detected. Here we report the observation of a large positive contribution to the magnetoconductance in the sliding mode of the Charge-Density-Wave Weyl semimetal (TaSe4)2I for collinear electric and magnetic fields. The positive contribution to the magnetoconductance originates from the anomalous axionic contribution of the chiral anomaly to the phason current, and is locked to the parallel alignment of the electric and magnetic fields. By rotating the magnetic field, we show that the angular dependence of the magnetoconductance is consistent with the anomalous transport of an axionic Charge-Density Wave. Our results show that it is possible to find experimental evidence for axions in strongly correlated topological condensed matter systems, which have so far been elusive in any other context. In the Charge-Density-Wave Weyl semimetal (TaSe4)2I, an axion is observed and identified as a sliding mode in the Charge-Density-Wave phase characterized by anomalous magnetoelectric transport effects.
Yan Sun - One of the best experts on this subject based on the ideXlab platform.
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A Charge-Density-Wave topological semimetal
Nature Physics, 2021Co-Authors: Wujun Shi, Yan Sun, Benjamin J. Wieder, Holger L. Meyerheim, Yang Zhang, Lei Shen, Lexian Yang, Jagannath JenaAbstract:Topological physics and strong electron–electron correlations in quantum materials are typically studied independently. However, there have been rapid recent developments in quantum materials in which topological phase transitions emerge when the single-particle band structure is modified by strong interactions. Here we demonstrate that the room-temperature phase of (TaSe4)2I is a Weyl semimetal with 24 pairs of Weyl nodes. Owing to its quasi-one-dimensional structure, (TaSe4)2I also hosts an established Charge-Density Wave instability just below room temperature. We show that the Charge-Density Wave in (TaSe4)2I couples the bulk Weyl points and opens a bandgap. The correlation-driven topological phase transition in (TaSe4)2I provides a route towards observing condensed-matter realizations of axion electrodynamics in the gapped regime, topological chiral response effects in the semimetallic phase, and represents an avenue for exploring the interplay of correlations and topology in a solid-state material. Strong electron–electron interactions create a Charge-Density Wave that modifies the topological state of the Weyl semimetal (TaSe4)2I. This implies the possibility of experimentally simulating axion electrodynamics in a solid-state material.
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axionic Charge Density Wave in the weyl semimetal tase4 2i
Nature, 2019Co-Authors: Johannes Gooth, Barry Bradlyn, S Honnali, Clemens Philipp Schindler, Neeraj Kumar, Jonathan Noky, C Shekhar, Yan Sun, Zixuan Wang, B A BernevigAbstract:An axion insulator is a correlated topological phase, which is predicted to arise from the formation of a Charge-Density Wave in a Weyl semimetal1,2—that is, a material in which electrons behave as massless chiral fermions. The accompanying sliding mode in the Charge-Density-Wave phase—the phason—is an axion3,4 and is expected to cause anomalous magnetoelectric transport effects. However, this axionic Charge-Density Wave has not yet been experimentally detected. Here we report the observation of a large positive contribution to the magnetoconductance in the sliding mode of the Charge-Density-Wave Weyl semimetal (TaSe4)2I for collinear electric and magnetic fields. The positive contribution to the magnetoconductance originates from the anomalous axionic contribution of the chiral anomaly to the phason current, and is locked to the parallel alignment of the electric and magnetic fields. By rotating the magnetic field, we show that the angular dependence of the magnetoconductance is consistent with the anomalous transport of an axionic Charge-Density Wave. Our results show that it is possible to find experimental evidence for axions in strongly correlated topological condensed matter systems, which have so far been elusive in any other context. In the Charge-Density-Wave Weyl semimetal (TaSe4)2I, an axion is observed and identified as a sliding mode in the Charge-Density-Wave phase characterized by anomalous magnetoelectric transport effects.
Jure Demsar - One of the best experts on this subject based on the ideXlab platform.
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ultrafast metamorphosis of a complex Charge Density Wave
Physical Review Letters, 2016Co-Authors: K Haupt, Jure Demsar, Maximilian Eichberger, N Erasmus, Andrea Rohwer, K Rossnagel, H SchwoererAbstract:Modulated phases, commensurate or incommensurate with the host crystal lattice, are ubiquitous in solids. The transition between such phases involves formation and rearrangement of domain walls and is generally slow. Using ultrafast electron diffraction, we directly record the photoinduced transformation between a nearly commensurate and an incommensurate Charge-Density-Wave phase in 1T-TaS(2). The transformation takes place on the picosecond time scale, orders of magnitude faster than previously observed for commensurate-to-incommensurate transitions. The transition speed and mechanism can be linked to the peculiar nanoscale structure of the photoexcited nearly commensurate phase.
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A multi-terahertz view of ultrafast Charge Density Wave dynamics in TiSe 2
CLEO: 2013, 2013Co-Authors: M. Porer, Jean-michel Ménard, H. Dachraoui, U. Leierseder, K. Groh, Jure Demsar, Ulrich Heinzmann, Robert HuberAbstract:We track the collective terahertz free-carrier response of 1T-TiSe 2 during femtosecond photo-induced melting and recovery of a Charge Density Wave. The formation of Charge order is highly sensitive to the transient excess carrier Density, suggesting a strong excitonic influence.
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Nonthermal melting of a Charge Density Wave in TiSe2.
Physical review letters, 2011Co-Authors: E. Möhr-vorobeva, Jure Demsar, Steven L. Johnson, Paul Beaud, Urs Staub, R. T. De Souza, Christopher J. Milne, Gerhard Ingold, H. Schaefer, Alexander TitovAbstract:We use time-resolved optical reflectivity and x-ray diffraction with femtosecond resolution to study the dynamics of the structural order parameter of the Charge Density Wave phase in TiSe2. We find that the energy Density required to melt the Charge Density Wave nonthermally is substantially lower than that required for thermal suppression and is comparable to the Charge Density Wave condensation energy. This observation, together with the fact that the structural dynamics take place on an extremely fast time scale, supports the exciton condensation mechanism for the Charge Density Wave in TiSe2.
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Nonthermal Melting of a Charge Density Wave in TiSe 2
Physical review letters, 2011Co-Authors: E. Möhr-vorobeva, Jure Demsar, Steven L. Johnson, Paul Beaud, Urs Staub, Christopher J. Milne, Gerhard Ingold, H. Schaefer, R. A. De Souza, Alexander TitovAbstract:We use time-resolved optical reflectivity and x-ray diffraction with femtosecond resolution to study the dynamics of the structural order parameter of the Charge Density Wave phase in TiSe2. We find that the energy Density required to melt the Charge Density Wave nonthermally is substantially lower than that required for thermal suppression and is comparable to the Charge Density Wave condensation energy. This observation, together with the fact that the structural dynamics take place on an extremely fast time scale, supports the exciton condensation mechanism for the Charge Density Wave in TiSe2.