Li Yin, Hong Tang, Tom Berlijn, Adrienn Ruzsinszky
Charge density waves (CDWs) in transition metal dichalcogenides are the subject of growing scientific interest due to their rich interplay with exotic phases of matter and their potential technological applications. Here, using density functional theory with advanced meta-generalized gradient approximations (meta-GGAs) and linear response time-dependent density functional theory (TDDFT) with state-of-the-art exchange-correlation kernels, we investigate the electronic, vibrational, and optical properties in 1T-TiSe2 with and without CDW. In both bulk and monolayer TiSe2, the electronic bands and phonon dispersions in either normal (semi-metallic) or CDW (semiconducting) phase are described well via meta-GGAs, which separate the valence and conduction bands just as HSE06 does but with significantly more computational feasibility. Instead of the underestimated gap with standard exchange-correlation approximations and the overestimated gap with screened hybrid functional HSE06, the band gap of the monolayer TiSe2 CDW phase calculated by the meta-GGA MVS (151 meV) is consistent with the angle-resolved photoemission spectroscopy (ARPES) gap of 153 meV measured at 10 K. In addition, the gap of bulk TiSe2 CDW phase reaches 67 meV within the TASK approximation, close to the ARPES gap of 82 meV. Regarding excitations of many-body nature, for bulk TiSe2 in normal and CDW phases, the experimentally observed humps of electron energy loss spectroscopy and plasmon peak are successfully reproduced in TDDFT, without an obvious kernel dependence. To unleash the full scientific and technological potential of CDWs in transition metal dichalcogenides, the chemical doping, heterostructure engineering, and pump-probe techniques are needed. Our study opens the door to simulating these complexities in CDW compounds from first principles by revealing meta-GGAs as an accurate low-cost alternative to HSE06.
{"title":"A Pathway to Efficient Simulations of Charge Density Waves in Transition Metal Dichalcogenides: A Case Study for TiSe2","authors":"Li Yin, Hong Tang, Tom Berlijn, Adrienn Ruzsinszky","doi":"arxiv-2404.07414","DOIUrl":"https://doi.org/arxiv-2404.07414","url":null,"abstract":"Charge density waves (CDWs) in transition metal dichalcogenides are the\u0000subject of growing scientific interest due to their rich interplay with exotic\u0000phases of matter and their potential technological applications. Here, using\u0000density functional theory with advanced meta-generalized gradient\u0000approximations (meta-GGAs) and linear response time-dependent density\u0000functional theory (TDDFT) with state-of-the-art exchange-correlation kernels,\u0000we investigate the electronic, vibrational, and optical properties in 1T-TiSe2\u0000with and without CDW. In both bulk and monolayer TiSe2, the electronic bands\u0000and phonon dispersions in either normal (semi-metallic) or CDW (semiconducting)\u0000phase are described well via meta-GGAs, which separate the valence and\u0000conduction bands just as HSE06 does but with significantly more computational\u0000feasibility. Instead of the underestimated gap with standard\u0000exchange-correlation approximations and the overestimated gap with screened\u0000hybrid functional HSE06, the band gap of the monolayer TiSe2 CDW phase\u0000calculated by the meta-GGA MVS (151 meV) is consistent with the angle-resolved\u0000photoemission spectroscopy (ARPES) gap of 153 meV measured at 10 K. In\u0000addition, the gap of bulk TiSe2 CDW phase reaches 67 meV within the TASK\u0000approximation, close to the ARPES gap of 82 meV. Regarding excitations of\u0000many-body nature, for bulk TiSe2 in normal and CDW phases, the experimentally\u0000observed humps of electron energy loss spectroscopy and plasmon peak are\u0000successfully reproduced in TDDFT, without an obvious kernel dependence. To\u0000unleash the full scientific and technological potential of CDWs in transition\u0000metal dichalcogenides, the chemical doping, heterostructure engineering, and\u0000pump-probe techniques are needed. Our study opens the door to simulating these\u0000complexities in CDW compounds from first principles by revealing meta-GGAs as\u0000an accurate low-cost alternative to HSE06.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effects of disorder on the robustness of topological magnon states of two-dimensional ferromagnetic skyrmions is investigated. It is diagnosed by evaluating a real space topological invariant, the bosonic Bott index (BI). The disorder simultaneously breaks the axially symmetric shape and the crystalline ordering of the skyrmions array. The corresponding magnonic fluctuations and band spectrum are determined in terms of magnetic field and strength of disorder. We observe the closing of the existing band gaps as the individual skyrmions start to occupy random positions. The analysis reveals that topological states (TSs) persist beyond the perturbative limit when skyrmions reach the glassy phase. In addition, the localization of topologically protected edge states is weakened by the disordered skyrmion structure with increasing localization length. Our findings shed light on the physical understanding of the coexistence of disordered magnetic textures and their topological spin fluctuations.
{"title":"Robustness of topological magnons in disordered arrays of skyrmions","authors":"H. Diego Rosales, Roberto E. Troncoso","doi":"arxiv-2404.06541","DOIUrl":"https://doi.org/arxiv-2404.06541","url":null,"abstract":"The effects of disorder on the robustness of topological magnon states of\u0000two-dimensional ferromagnetic skyrmions is investigated. It is diagnosed by\u0000evaluating a real space topological invariant, the bosonic Bott index (BI). The\u0000disorder simultaneously breaks the axially symmetric shape and the crystalline\u0000ordering of the skyrmions array. The corresponding magnonic fluctuations and\u0000band spectrum are determined in terms of magnetic field and strength of\u0000disorder. We observe the closing of the existing band gaps as the individual\u0000skyrmions start to occupy random positions. The analysis reveals that\u0000topological states (TSs) persist beyond the perturbative limit when skyrmions\u0000reach the glassy phase. In addition, the localization of topologically\u0000protected edge states is weakened by the disordered skyrmion structure with\u0000increasing localization length. Our findings shed light on the physical\u0000understanding of the coexistence of disordered magnetic textures and their\u0000topological spin fluctuations.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"123 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao Zhang, Massimo Boninsegni, Anatoly Kuklov, Nikolay Prokof'ev, Boris Svistunov
Superclimbing modes are hallmark degrees of freedom of transverse quantum fluids describing wide superfluid one-dimensional interfaces and/or edges with negligible Peierls barrier. We report the first direct numeric evidence of quantum shape fluctuations -- caused by superclimbing modes -- in simple lattice models, as well as at the free edge of an incomplete solid monolayer of $^4$He adsorbed on graphite. Our data unambiguously reveals the defining feature of the superclimbing modes -- canonical conjugation of the edge displacement field to the field of superfluid phase -- and its unexpected implication, i.e., that superfluid stiffness can be inferred from density snapshots.
{"title":"Superclimbing modes in transverse quantum fluids: signature statistical and dynamical features","authors":"Chao Zhang, Massimo Boninsegni, Anatoly Kuklov, Nikolay Prokof'ev, Boris Svistunov","doi":"arxiv-2404.03465","DOIUrl":"https://doi.org/arxiv-2404.03465","url":null,"abstract":"Superclimbing modes are hallmark degrees of freedom of transverse quantum\u0000fluids describing wide superfluid one-dimensional interfaces and/or edges with\u0000negligible Peierls barrier. We report the first direct numeric evidence of\u0000quantum shape fluctuations -- caused by superclimbing modes -- in simple\u0000lattice models, as well as at the free edge of an incomplete solid monolayer of\u0000$^4$He adsorbed on graphite. Our data unambiguously reveals the defining\u0000feature of the superclimbing modes -- canonical conjugation of the edge\u0000displacement field to the field of superfluid phase -- and its unexpected\u0000implication, i.e., that superfluid stiffness can be inferred from density\u0000snapshots.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rahul Gupta, Chloé Bouard, Fabian Kammerbauer, J. Omar Ledesma-Martin, Iryna Kononenko, Sylvain Martin, Gerhard Jakob, Marc Drouard, Mathias Kläui
Spin-Orbit Torque (SOT) Magnetic Random-Access Memory (MRAM) devices offer improved power efficiency, nonvolatility, and performance compared to static RAM, making them ideal, for instance, for cache memory applications. Efficient magnetization switching, long data retention, and high-density integration in SOT MRAM require ferromagnets (FM) with perpendicular magnetic anisotropy (PMA) combined with large torques enhanced by Orbital Hall Effect (OHE). We have engineered PMA [Co/Ni]$_3$ FM on selected OHE layers (Ru, Nb, Cr) and investigated the potential of theoretically predicted larger orbital Hall conductivity (OHC) to quantify the torque and switching current in OHE/[Co/Ni]$_3$ stacks. Our results demonstrate a $sim$30% enhancement in damping-like torque efficiency with a positive sign for the Ru OHE layer compared to a pure Pt, accompanied by a $sim$20% reduction in switching current for Ru compared to pure Pt across more than 250 devices, leading to more than a 60% reduction in switching power. These findings validate the application of Ru in devices relevant to industrial contexts, supporting theoretical predictions regarding its superior OHC. This investigation highlights the potential of enhanced orbital torques to improve the performance of orbital-assisted SOT-MRAM, paving the way for next-generation memory technology.
{"title":"Harnessing Orbital Hall Effect in Spin-Orbit Torque MRAM","authors":"Rahul Gupta, Chloé Bouard, Fabian Kammerbauer, J. Omar Ledesma-Martin, Iryna Kononenko, Sylvain Martin, Gerhard Jakob, Marc Drouard, Mathias Kläui","doi":"arxiv-2404.02821","DOIUrl":"https://doi.org/arxiv-2404.02821","url":null,"abstract":"Spin-Orbit Torque (SOT) Magnetic Random-Access Memory (MRAM) devices offer\u0000improved power efficiency, nonvolatility, and performance compared to static\u0000RAM, making them ideal, for instance, for cache memory applications. Efficient\u0000magnetization switching, long data retention, and high-density integration in\u0000SOT MRAM require ferromagnets (FM) with perpendicular magnetic anisotropy (PMA)\u0000combined with large torques enhanced by Orbital Hall Effect (OHE). We have\u0000engineered PMA [Co/Ni]$_3$ FM on selected OHE layers (Ru, Nb, Cr) and\u0000investigated the potential of theoretically predicted larger orbital Hall\u0000conductivity (OHC) to quantify the torque and switching current in\u0000OHE/[Co/Ni]$_3$ stacks. Our results demonstrate a $sim$30% enhancement in\u0000damping-like torque efficiency with a positive sign for the Ru OHE layer\u0000compared to a pure Pt, accompanied by a $sim$20% reduction in switching\u0000current for Ru compared to pure Pt across more than 250 devices, leading to\u0000more than a 60% reduction in switching power. These findings validate the\u0000application of Ru in devices relevant to industrial contexts, supporting\u0000theoretical predictions regarding its superior OHC. This investigation\u0000highlights the potential of enhanced orbital torques to improve the performance\u0000of orbital-assisted SOT-MRAM, paving the way for next-generation memory\u0000technology.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pietro Tassan, Darius Urbonas, Bartos Chmielak, Jens Bolten, Thorsten Wahlbrink, Max C. Lemme, Michael Forster, Ullrich Scherf, Rainer F. Mahrt, Thilo Stöferle
The clock speed of electronic circuits has been stagnant at a few gigahertz for almost two decades because of the breakdown of Dennard scaling, which states that by shrinking the size of transistors they can operate faster while maintaining the same power consumption. Optical computing could overcome this roadblock, but the lack of materials with suitably strong nonlinear interactions needed to realize all-optical switches has, so far, precluded the fabrication of scalable architectures. Recently, microcavities in the strong light-matter interaction regime enabled all-optical transistors which, when used with an embedded organic material, can operate even at room temperature with sub-picosecond switching times, down to the single-photon level. However, the vertical cavity geometry prevents complex circuits with on-chip coupled transistors. Here, by leveraging silicon photonics technology, we show exciton-polariton condensation at ambient conditions in micrometer-sized, fully integrated high-index contrast grating microcavities filled with an optically active polymer. By coupling two resonators and exploiting seeded polariton condensation, we demonstrate ultrafast all-optical transistor action and cascadability. Our experimental findings open the way for scalable, compact all-optical integrated logic circuits that could process optical signals two orders of magnitude faster than their electrical counterparts.
{"title":"Integrated ultrafast all-optical polariton transistors","authors":"Pietro Tassan, Darius Urbonas, Bartos Chmielak, Jens Bolten, Thorsten Wahlbrink, Max C. Lemme, Michael Forster, Ullrich Scherf, Rainer F. Mahrt, Thilo Stöferle","doi":"arxiv-2404.01868","DOIUrl":"https://doi.org/arxiv-2404.01868","url":null,"abstract":"The clock speed of electronic circuits has been stagnant at a few gigahertz\u0000for almost two decades because of the breakdown of Dennard scaling, which\u0000states that by shrinking the size of transistors they can operate faster while\u0000maintaining the same power consumption. Optical computing could overcome this\u0000roadblock, but the lack of materials with suitably strong nonlinear\u0000interactions needed to realize all-optical switches has, so far, precluded the\u0000fabrication of scalable architectures. Recently, microcavities in the strong\u0000light-matter interaction regime enabled all-optical transistors which, when\u0000used with an embedded organic material, can operate even at room temperature\u0000with sub-picosecond switching times, down to the single-photon level. However,\u0000the vertical cavity geometry prevents complex circuits with on-chip coupled\u0000transistors. Here, by leveraging silicon photonics technology, we show\u0000exciton-polariton condensation at ambient conditions in micrometer-sized, fully\u0000integrated high-index contrast grating microcavities filled with an optically\u0000active polymer. By coupling two resonators and exploiting seeded polariton\u0000condensation, we demonstrate ultrafast all-optical transistor action and\u0000cascadability. Our experimental findings open the way for scalable, compact\u0000all-optical integrated logic circuits that could process optical signals two\u0000orders of magnitude faster than their electrical counterparts.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhaoyu Liu, Xuetao Ma, John Cenker, Jiaqi Cai, Zaiyao Fei, Paul Malinowski, Joshua Mutch, Yuzho Zhao, Kyle Hwangbo, Zhong Lin, Arnab Manna, Jihui Yang, David Cobden, Xiaodong Xu, Matthew Yankowitz, Jiun-Haw Chu
Uniaxial strain has been widely used as a powerful tool for investigating and controlling the properties of quantum materials. However, existing strain techniques have so far mostly been limited to use with bulk crystals. Although recent progress has been made in extending the application of strain to two-dimensional van der Waals (vdW) heterostructures, these techniques have been limited to optical characterization and extremely simple electrical device geometries. Here, we report a piezoelectric-based in-situ uniaxial strain technique enabling simultaneous electrical transport and optical spectroscopy characterization of dual-gated vdW heterostructure devices. Critically, our technique remains compatible with vdW heterostructure devices of arbitrary complexity fabricated on conventional silicon/silicon dioxide wafer substrates. We demonstrate a large and continuously tunable strain of up to $0.15$% at millikelvin temperatures, with larger strain values also likely achievable. We quantify the strain transmission from the silicon wafer to the vdW heterostructure, and further demonstrate the ability of strain to modify the electronic properties of twisted bilayer graphene. Our technique provides a highly versatile new method for exploring the effect of uniaxial strain on both the electrical and optical properties of vdW heterostructures, and can be easily extended to include additional characterization techniques.
{"title":"Continuously tunable uniaxial strain control of van der Waals heterostructure devices","authors":"Zhaoyu Liu, Xuetao Ma, John Cenker, Jiaqi Cai, Zaiyao Fei, Paul Malinowski, Joshua Mutch, Yuzho Zhao, Kyle Hwangbo, Zhong Lin, Arnab Manna, Jihui Yang, David Cobden, Xiaodong Xu, Matthew Yankowitz, Jiun-Haw Chu","doi":"arxiv-2404.00905","DOIUrl":"https://doi.org/arxiv-2404.00905","url":null,"abstract":"Uniaxial strain has been widely used as a powerful tool for investigating and\u0000controlling the properties of quantum materials. However, existing strain\u0000techniques have so far mostly been limited to use with bulk crystals. Although\u0000recent progress has been made in extending the application of strain to\u0000two-dimensional van der Waals (vdW) heterostructures, these techniques have\u0000been limited to optical characterization and extremely simple electrical device\u0000geometries. Here, we report a piezoelectric-based in-situ uniaxial strain\u0000technique enabling simultaneous electrical transport and optical spectroscopy\u0000characterization of dual-gated vdW heterostructure devices. Critically, our\u0000technique remains compatible with vdW heterostructure devices of arbitrary\u0000complexity fabricated on conventional silicon/silicon dioxide wafer substrates.\u0000We demonstrate a large and continuously tunable strain of up to $0.15$% at\u0000millikelvin temperatures, with larger strain values also likely achievable. We\u0000quantify the strain transmission from the silicon wafer to the vdW\u0000heterostructure, and further demonstrate the ability of strain to modify the\u0000electronic properties of twisted bilayer graphene. Our technique provides a\u0000highly versatile new method for exploring the effect of uniaxial strain on both\u0000the electrical and optical properties of vdW heterostructures, and can be\u0000easily extended to include additional characterization techniques.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study magnetotransport in conical helimagnet crystals. Spin dependent magnetoresistance exhibits dramatic properties for high and low electron concentrations at different temperatures. For spin up electrons we find negative magnetoresistance despite only considering a single carrier type. For spin down electrons we observe giant magnetoresistance due to depletion of spin down electrons with an applied magnetic field. For spin up carriers, the magnetoresistance is negative, due to the increase in charge carriers with a magnetic field. In addition, we investigate spin dependent Hall effect. If a magnetic field reaches some critical value for spin down electrons, giant Hall resistance occurs, i.e., Hall current vanishes. This effect is explained by the absence of spin down carriers. For spin up carriers, the Hall constant dramatically decreases with field, due to the increase in spin up electron density. Because of the giant spin dependent magnetoresistance and Hall resistivity, conical helimagnets could be useful in spin switching devices.
{"title":"Giant and negative magnetoresistances in conical magnets","authors":"Raz Rivlis, Andrei Zadorozhnyi, Yuri Dahnovsky","doi":"arxiv-2404.01401","DOIUrl":"https://doi.org/arxiv-2404.01401","url":null,"abstract":"We study magnetotransport in conical helimagnet crystals. Spin dependent\u0000magnetoresistance exhibits dramatic properties for high and low electron\u0000concentrations at different temperatures. For spin up electrons we find\u0000negative magnetoresistance despite only considering a single carrier type. For\u0000spin down electrons we observe giant magnetoresistance due to depletion of spin\u0000down electrons with an applied magnetic field. For spin up carriers, the\u0000magnetoresistance is negative, due to the increase in charge carriers with a\u0000magnetic field. In addition, we investigate spin dependent Hall effect. If a\u0000magnetic field reaches some critical value for spin down electrons, giant Hall\u0000resistance occurs, i.e., Hall current vanishes. This effect is explained by the\u0000absence of spin down carriers. For spin up carriers, the Hall constant\u0000dramatically decreases with field, due to the increase in spin up electron\u0000density. Because of the giant spin dependent magnetoresistance and Hall\u0000resistivity, conical helimagnets could be useful in spin switching devices.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ioannis Kiorpelidis, Fotios K. Diakonos, Georgios Theocharis, Vincent Pagneux
The Mathieu equation occurs naturally in the description of non linear vibrations or by considering the propagation of a wave in an infinite medium with time-periodic refractive index. It is known to lead to parametric instability since it supports unstable solutions in some regions of the parameter space. However, even in the stable region the matrix that propagates the initial conditions forward in time is non-normal and therefore it can result in transient amplification. By optimizing over initial conditions as well as initial time we show that significant transient amplifications can be obtained, going beyond the one simply stemming from adiabatic invariance. Moreover, we explore the monodromy matrix in more depth, by studying its $epsilon$-pseudospectra and Petermann factors, demonstrating that is the degree of non-normality of this matrix that determines the global amplifying features.
{"title":"Transient amplification in Floquet media: the Mathieu oscillator example","authors":"Ioannis Kiorpelidis, Fotios K. Diakonos, Georgios Theocharis, Vincent Pagneux","doi":"arxiv-2404.00138","DOIUrl":"https://doi.org/arxiv-2404.00138","url":null,"abstract":"The Mathieu equation occurs naturally in the description of non linear\u0000vibrations or by considering the propagation of a wave in an infinite medium\u0000with time-periodic refractive index. It is known to lead to parametric\u0000instability since it supports unstable solutions in some regions of the\u0000parameter space. However, even in the stable region the matrix that propagates\u0000the initial conditions forward in time is non-normal and therefore it can\u0000result in transient amplification. By optimizing over initial conditions as\u0000well as initial time we show that significant transient amplifications can be\u0000obtained, going beyond the one simply stemming from adiabatic invariance.\u0000Moreover, we explore the monodromy matrix in more depth, by studying its\u0000$epsilon$-pseudospectra and Petermann factors, demonstrating that is the\u0000degree of non-normality of this matrix that determines the global amplifying\u0000features.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"2011 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Excitons in van der Waals heterostructures based on atomically thin transition metal dichalcogenides are considered as potential candidates for the formation of a superfluid state in two-dimensional systems. A number of studies reported observations of ultrafast nondiffusive propagation of excitons in van der Waals heterostructures, which was considered by their authors as possible evidence of collective effects in excitonic systems. In this paper, after a brief analysis of exciton propagation regimes in two-dimensional semiconductors, an alternative model of ultrafast exciton transport is proposed, based on the formation of waveguide modes in van der Waals heterostructures and the radiation transfer by these modes.
{"title":"Ultrafast exciton transport in van der Waals heterostructures","authors":"M. M. Glazov, R. A. Suris","doi":"arxiv-2403.19571","DOIUrl":"https://doi.org/arxiv-2403.19571","url":null,"abstract":"Excitons in van der Waals heterostructures based on atomically thin\u0000transition metal dichalcogenides are considered as potential candidates for the\u0000formation of a superfluid state in two-dimensional systems. A number of studies\u0000reported observations of ultrafast nondiffusive propagation of excitons in van\u0000der Waals heterostructures, which was considered by their authors as possible\u0000evidence of collective effects in excitonic systems. In this paper, after a\u0000brief analysis of exciton propagation regimes in two-dimensional\u0000semiconductors, an alternative model of ultrafast exciton transport is\u0000proposed, based on the formation of waveguide modes in van der Waals\u0000heterostructures and the radiation transfer by these modes.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140324765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Mincigrucci, E. Paltanin, J. -S. Pelli-Cresi, F. Gala, E. Pontecorvo, L. Foglia, D. De Angelis, D. Fainozzi, A. Gessini, D. S. P. Molina, O. Stranik, F. Wechsler, R. Heintzmann, G. Ruocco, F. Bencivenga, C. Masciovecchio
The relentless pursuit of understanding matter at ever-finer scales has pushed optical microscopy to surpass the diffraction limit and produced the super-resolution microscopy which enables visualizing structures shorter than the wavelength of light. In the present work, we harnessed extreme ultraviolet beams to create a sub-{mu}m grating structure, which was revealed by extreme ultraviolet structured illumination microscopy. This achievement marks the first step toward extending such a super-resolution technique into the X-ray regime, where achieving atomic-scale resolution becomes a charming possibility.
{"title":"Structured illumination microscopy with extreme ultraviolet pulses","authors":"R. Mincigrucci, E. Paltanin, J. -S. Pelli-Cresi, F. Gala, E. Pontecorvo, L. Foglia, D. De Angelis, D. Fainozzi, A. Gessini, D. S. P. Molina, O. Stranik, F. Wechsler, R. Heintzmann, G. Ruocco, F. Bencivenga, C. Masciovecchio","doi":"arxiv-2403.19382","DOIUrl":"https://doi.org/arxiv-2403.19382","url":null,"abstract":"The relentless pursuit of understanding matter at ever-finer scales has\u0000pushed optical microscopy to surpass the diffraction limit and produced the\u0000super-resolution microscopy which enables visualizing structures shorter than\u0000the wavelength of light. In the present work, we harnessed extreme ultraviolet\u0000beams to create a sub-{mu}m grating structure, which was revealed by extreme\u0000ultraviolet structured illumination microscopy. This achievement marks the\u0000first step toward extending such a super-resolution technique into the X-ray\u0000regime, where achieving atomic-scale resolution becomes a charming possibility.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"87 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140324740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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