1
|
Torbatian Z, Novko D. Plasmon Excitations across the Charge-Density-Wave Transition in Single-Layer TiSe 2. J Phys Chem Lett 2024; 15:6045-6050. [PMID: 38819234 DOI: 10.1021/acs.jpclett.4c01034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
1T-TiSe2 is believed to possess a soft electronic mode, i.e., plasmon or exciton, that might be responsible for the exciton condensation and charge-density-wave (CDW) transition. Here, we explore collective electronic excitations in single-layer 1T-TiSe2 by using the ab initio electromagnetic linear response and unveil intricate scattering pathways of the two-dimensional (2D) plasmon mode near the CDW phase. We found the dominant role of plasmon-phonon scattering, which in combination with the CDW gap excitations leads to the anomalous temperature dependence of the plasmon line width across the CDW transition. Below the transition temperature TCDW a strong hybridization between the 2D plasmon and CDW excitations is obtained. These optical features are highly tunable due to temperature-dependent CDW-related modifications of electronic structure and electron-phonon coupling and make CDW-bearing systems potentially interesting for applications in optoelectronics and low-loss plasmonics.
Collapse
Affiliation(s)
- Zahra Torbatian
- School of Nano Science, Institute for Research in Fundamental Sciences (IPM), 19395-5531 Tehran, Iran
| | - Dino Novko
- Centre for Advanced Laser Techniques, Institute of Physics, 10000 Zagreb, Croatia
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
| |
Collapse
|
2
|
Huber M, Lin Y, Marini G, Moreschini L, Jozwiak C, Bostwick A, Calandra M, Lanzara A. Ultrafast creation of a light-induced semimetallic state in strongly excited 1T-TiSe 2. SCIENCE ADVANCES 2024; 10:eadl4481. [PMID: 38728393 PMCID: PMC11086600 DOI: 10.1126/sciadv.adl4481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 04/09/2024] [Indexed: 05/12/2024]
Abstract
Screening, a ubiquitous phenomenon associated with the shielding of electric fields by surrounding charges, has been widely adopted as a means to modify a material's properties. While most studies have relied on static changes of screening through doping or gating thus far, here we demonstrate that screening can also drive the onset of distinct quantum states on the ultrafast timescale. By using time- and angle-resolved photoemission spectroscopy, we show that intense optical excitation can drive 1T-TiSe2, a prototypical charge density wave material, almost instantly from a gapped into a semimetallic state. By systematically comparing changes in band structure over time and excitation strength with theoretical calculations, we find that the appearance of this state is likely caused by a dramatic reduction of the screening length. In summary, this work showcases how optical excitation enables the screening-driven design of a nonequilibrium semimetallic phase in TiSe2, possibly providing a general pathway into highly screened phases in other strongly correlated materials.
Collapse
Affiliation(s)
- Maximilian Huber
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Yi Lin
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA
| | - Giovanni Marini
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, I-16163 Genova, Italy
- Department of Physics, University of Trento, 38123 Povo, Italy
| | - Luca Moreschini
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Chris Jozwiak
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Aaron Bostwick
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Matteo Calandra
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, I-16163 Genova, Italy
- Department of Physics, University of Trento, 38123 Povo, Italy
- Sorbonne Universite, CNRS, Institut des Nanosciences de Paris, F-75252 Paris, France
| | - Alessandra Lanzara
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Physics Department, University of California, Berkeley, Berkeley, CA 94720, USA
- Kavli Energy NanoScience Institute, Berkeley, CA 94720, USA
| |
Collapse
|
3
|
Wang C, Liu X, Chen Q, Chen D, Wang Y, Meng S. Coherent-Phonon-Driven Intervalley Scattering and Rabi Oscillation in Multivalley 2D Materials. PHYSICAL REVIEW LETTERS 2023; 131:066401. [PMID: 37625067 DOI: 10.1103/physrevlett.131.066401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 05/15/2023] [Accepted: 06/29/2023] [Indexed: 08/27/2023]
Abstract
Resolving the complete electron scattering dynamics mediated by coherent phonons is crucial for understanding electron-phonon couplings beyond equilibrium. Here we present a time-resolved theoretical investigation on strongly coupled ultrafast electron and phonon dynamics in monolayer WSe_{2}, with a focus on the intervalley scattering from the optically "bright" K state to "dark" Q state. We find that the strong coherent lattice vibration along the longitudinal acoustic phonon mode [LA(M)] can drastically promote K-to-Q transition on a timescale of ∼400 fs, comparable with previous experimental observation on thermal-phonon-mediated electron dynamics. Further, this coherent-phonon-driven intervalley scattering occurs in an unconventional steplike manner and further induces an electronic Rabi oscillation. By constructing a two-level model and quantitatively comparing with ab initio dynamic simulations, we uncover the critical role of nonadiabatic coupling effects. Finally, a new strategy is proposed to effectively tune the intervalley scattering rates by varying the coherent phonon amplitude, which could be realized via light-induced nonlinear phononics that we hope will spark experimental investigation.
Collapse
Affiliation(s)
- Chenyu Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Xinbao Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Qing Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Daqiang Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yaxian Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| |
Collapse
|
4
|
Jaouen T, Pulkkinen A, Rumo M, Kremer G, Salzmann B, Nicholson CW, Mottas ML, Giannini E, Tricot S, Schieffer P, Hildebrand B, Monney C. Carrier-Density Control of the Quantum-Confined 1T-TiSe_{2} Charge Density Wave. PHYSICAL REVIEW LETTERS 2023; 130:226401. [PMID: 37327408 DOI: 10.1103/physrevlett.130.226401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 05/10/2023] [Indexed: 06/18/2023]
Abstract
Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schrödinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of 1T-TiSe_{2} induce the creation of a two-dimensional electron gas (2DEG) and quantum confinement of its charge-density wave (CDW) at the surface. By further changing the K coverage, we tune the carrier density within the 2DEG that allows us to nullify, at the surface, the electronic energy gain due to exciton condensation in the CDW phase while preserving a long-range structural order. Our Letter constitutes a prime example of a controlled exciton-related many-body quantum state in reduced dimensionality by alkali-metal dosing.
Collapse
Affiliation(s)
- T Jaouen
- Univ Rennes, CNRS, (IPR Institut de Physique de Rennes)-UMR 6251, F-35000 Rennes, France
| | - A Pulkkinen
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
- New Technologies Research Centre, University of West Bohemia, CZ-30100 Pilsen, Czech Republic
| | - M Rumo
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
- Haute école d'ingénierie et d'architecture de Fribourg, CH-1700 Fribourg, Switzerland
| | - G Kremer
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
- Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, 54011 Nancy, France
| | - B Salzmann
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
| | - C W Nicholson
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
- Fritz-Haber-Institute der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - M-L Mottas
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
| | - E Giannini
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - S Tricot
- Univ Rennes, CNRS, (IPR Institut de Physique de Rennes)-UMR 6251, F-35000 Rennes, France
| | - P Schieffer
- Univ Rennes, CNRS, (IPR Institut de Physique de Rennes)-UMR 6251, F-35000 Rennes, France
| | - B Hildebrand
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
| | - C Monney
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
| |
Collapse
|
5
|
Huang Y, Lv S, Liu H, Cheng Q, Biao Y, Lu H, Lin X, Wang Z, Yang H, Chen H, Weng YX. Observation of photoinduced polarons in semimetal 1T-TiSe 2. NANOTECHNOLOGY 2023; 34:235707. [PMID: 36877995 DOI: 10.1088/1361-6528/acc188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 03/05/2023] [Indexed: 06/18/2023]
Abstract
In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe2flakes from the high-quality single crystals with self-intercalated Ti atoms are investigated by femtosecond transient absorption spectroscopy. The observed coherent acoustic and optical phonon oscillations after ultrafast photoexcitation reveal the strong electron-phonon coupling in 1T-TiSe2. The ultrafast carrier dynamics probed in both visible and mid-infrared regions indicate that some photogenerated carriers localize near the intercalated Ti atoms and form small polarons rapidly within several picoseconds after photoexcitation due to the strong and short-range electron-phonon coupling. The formation of polarons leads to a reduction of carrier mobility and a long-time relaxation process of photoexcited carriers for several nanoseconds. The formation and dissociation rates of the photoinduced polarons are dependent on both the pump fluence and the thickness of TiSe2sample. This work offers new insights into the photogenerated carrier dynamics of 1T-TiSe2, and emphasizes the effects of intercalated atoms on the electron and lattice dynamics after photoexcitation.
Collapse
Affiliation(s)
- Yin Huang
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Senhao Lv
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Heyuan Liu
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Qiuzhen Cheng
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Yi Biao
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Hongliang Lu
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Xiao Lin
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Zhuan Wang
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Haitao Yang
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, People's Republic of China
| | - Hailong Chen
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, People's Republic of China
| | - Yu-Xiang Weng
- Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, People's Republic of China
| |
Collapse
|
6
|
Huber M, Lin Y, Dale N, Sailus R, Tongay S, Kaindl RA, Lanzara A. Revealing the order parameter dynamics of 1T-TiSe[Formula: see text] following optical excitation. Sci Rep 2022; 12:15860. [PMID: 36151110 PMCID: PMC9508156 DOI: 10.1038/s41598-022-19319-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 08/26/2022] [Indexed: 11/09/2022] Open
Abstract
The formation of a charge density wave state is characterized by an order parameter. The way it is established provides unique information on both the role that correlation plays in driving the charge density wave formation and the mechanism behind its formation. Here we use time and angle resolved photoelectron spectroscopy to optically perturb the charge-density phase in 1T-TiSe[Formula: see text] and follow the recovery of its order parameter as a function of energy, momentum and excitation density. Our results reveal that two distinct orders contribute to the gap formation, a CDW order and pseudogap-like order, manifested by an overall robustness to optical excitation. A detailed analysis of the magnitude of the the gap as a function of excitation density and delay time reveals the excitonic long-range nature of the CDW gap and the short-range Jahn-Teller character of the pseudogap order. In contrast to the gap, the intensity of the folded Se[Formula: see text]* band can only give access to the excitonic order. These results provide new information into the the long standing debate on the origin of the gap in TiSe[Formula: see text] and place it in the same context of other quantum materials where a pseudogap phase appears to be a precursor of long-range order.
Collapse
Affiliation(s)
- Maximilian Huber
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Yi Lin
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Nicholas Dale
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
- Physics Department, University of California Berkeley, Berkeley, CA 94720 USA
| | - Renee Sailus
- Materials Science and Engineering Department, Arizona State University, Phoenix, AZ 85281 USA
| | - Sefaattin Tongay
- Materials Science and Engineering Department, Arizona State University, Phoenix, AZ 85281 USA
| | - Robert A. Kaindl
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
- Department of Physics and CXFEL Labs, Arizona State University, Phoenix, AZ 85287 USA
| | - Alessandra Lanzara
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
- Physics Department, University of California Berkeley, Berkeley, CA 94720 USA
| |
Collapse
|
7
|
Spera M, Scarfato A, Pásztor Á, Giannini E, Bowler DR, Renner C. Insight into the Charge Density Wave Gap from Contrast Inversion in Topographic STM Images. PHYSICAL REVIEW LETTERS 2020; 125:267603. [PMID: 33449793 DOI: 10.1103/physrevlett.125.267603] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/23/2020] [Accepted: 12/01/2020] [Indexed: 06/12/2023]
Abstract
Charge density waves (CDWs) are understood in great detail in one dimension, but they remain largely enigmatic in two-dimensional systems. In particular, numerous aspects of the associated energy gap and the formation mechanism are not fully understood. Two long-standing riddles are the amplitude and position of the CDW gap with respect to the Fermi level (E_{F}) and the frequent absence of CDW contrast inversion (CI) between opposite bias scanning tunneling microscopy (STM) images. Here, we find compelling evidence that these two issues are intimately related. Combining density functional theory and STM to analyze the CDW pattern and modulation amplitude in 1T-TiSe_{2}, we find that CI takes place at an unexpected negative sample bias because the CDW gap opens away from E_{F}, deep inside the valence band. This bias becomes increasingly negative as the CDW gap shifts to higher binding energy with electron doping. This study shows the importance of CI in STM images to identify periodic modulations with a CDW and to gain valuable insight into the CDW gap, whose measurement is notoriously controversial.
Collapse
Affiliation(s)
- M Spera
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - A Scarfato
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Á Pásztor
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - E Giannini
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - D R Bowler
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - Ch Renner
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| |
Collapse
|
8
|
Hu Q, Xu S, Guo X, Liu H, Chen Z, Wang B, Ang R. Superconductivity related to the suppression of exciton formation in 1T-TiSe 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:425602. [PMID: 32720648 DOI: 10.1088/1361-648x/aba1ab] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/01/2020] [Indexed: 06/11/2023]
Abstract
In strongly correlated electron system, the impact of elementary substitution or intercalation plays a crucial role in determining electronic ground state among various macroscopic quantum phases such as charge order and superconductivity. Here, we report that simultaneous Cu intercalation and Ta substitution at Ti site in 1T-CuxTi0.8Ta0.2Se2induce an intrinsic electronic phase diagram, characterized by an inherent superconducting transition in thexregion of 0 ⩽x⩽ 0.12, with a maximum superconducting transition temperatureTcof 2.5 K forx= 0.04, in contrast to the non-superconducting sample 1T-Cu0.04TiSe2. The increased density of free charge carriers screen the Coulomb interaction between electron-hole pairs effectively, promoting the occurrence of superconductivity favourably. Present results suggest that the Cu intercalation and the Ta substitution-induced suppression of the exciton condensation boost the superconductivity, shedding new light on the fundamental physics of the interplay between superconductivity, charge order, and electron correlation.
Collapse
Affiliation(s)
- Qing Hu
- Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China
| | - Shuxiang Xu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Xuming Guo
- Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China
| | - Hangtian Liu
- Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China
| | - Zhiyu Chen
- Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China
| | - Bosen Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Ran Ang
- Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China
- Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610065, People's Republic of China
| |
Collapse
|
9
|
Zhou JS, Monacelli L, Bianco R, Errea I, Mauri F, Calandra M. Anharmonicity and Doping Melt the Charge Density Wave in Single-Layer TiSe 2. NANO LETTERS 2020; 20:4809-4815. [PMID: 32496779 DOI: 10.1021/acs.nanolett.0c00597] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Low-dimensional systems with a vanishing band gap and a large electron-hole interaction have been proposed to be unstable toward exciton formation. As the exciton binding energy increases in low dimension, conventional wisdom suggests that excitonic insulators should be more stable in 2D than in 3D. Here we study the effects of the electron-hole interaction and anharmonicity in single-layer TiSe2. We find that, contrary to the bulk case and to the generally accepted picture, in single-layer TiSe2, the electron-hole exchange interaction is much smaller in 2D than in 3D and it has weak effects on phonon spectra. By calculating anharmonic phonon spectra within the stochastic self-consistent harmonic approximation, we obtain TCDW ≈ 440 K for an isolated and undoped single layer and TCDW ≈ 364 K for an electron-doping n = 4.6 × 1013 cm-2, close to the experimental result of 200-280 K on supported samples. Our work demonstrates that anharmonicity and doping melt the charge density wave in single-layer TiSe2.
Collapse
Affiliation(s)
- Jianqiang Sky Zhou
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252, Paris, France
| | - Lorenzo Monacelli
- Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, I-00185 Roma, Italy
| | - Raffaello Bianco
- Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Ion Errea
- Fisika Aplikatua 1 Saila, Gipuzkoako Ingeniaritza Eskola, University of the Basque Country (UPV/EHU), Europa Plaza 1, 20018 Donostia-San Sebastián, Basque Country, Spain
- Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia-San Sebastián, Basque Country, Spain
- Donostia International Physics Center (DIPC), Manuel de Lardizabal pasealekua 4, 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Francesco Mauri
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 5, I-00185 Roma, Italy
- Graphene Laboratories, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
| | - Matteo Calandra
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252, Paris, France
- Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy
| |
Collapse
|
10
|
Shkvarin AS, Yarmoshenko YM, Merentsov AI, Shkvarina EG, Gubkin AF, Píš I, Nappini S, Bondino F, Bobrikov IA, Titov AN. Electronic Structures of the Vanadium-Intercalated and Substitutionally Doped Transition-Metal Dichalcogenides Ti xV ySe 2. Inorg Chem 2020; 59:8543-8551. [PMID: 32453586 DOI: 10.1021/acs.inorgchem.0c00953] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electronic structures of V-intercalated TiSe2 and substitutionally doped dichalcogenides Ti1-xVxSe2 have been studied using soft X-ray photoelectron, resonant photoelectron, and absorption spectroscopies. In the case of the substitution of Ti by V, the formation of coherently oriented structural fragments VSe2 and TiSe2 is observed and a small charge transfer between these fragments is found. Intercalation of the V atoms into TiSe2 leads to charge transfer from the V atoms to the Ti atoms with the formation of covalent complexes Ti-Se3-V-Se3-Ti.
Collapse
Affiliation(s)
- Alexey S Shkvarin
- M. N. Miheev Institute of Metal Physics of Ural Branch (UrD) of Russian Academy of Sciences (RAS), 620990 Ekaterinburg, Russia
| | - Yury M Yarmoshenko
- M. N. Miheev Institute of Metal Physics of Ural Branch (UrD) of Russian Academy of Sciences (RAS), 620990 Ekaterinburg, Russia
| | - Alexander I Merentsov
- M. N. Miheev Institute of Metal Physics of Ural Branch (UrD) of Russian Academy of Sciences (RAS), 620990 Ekaterinburg, Russia
| | - Elena G Shkvarina
- M. N. Miheev Institute of Metal Physics of Ural Branch (UrD) of Russian Academy of Sciences (RAS), 620990 Ekaterinburg, Russia
| | - Andrei F Gubkin
- M. N. Miheev Institute of Metal Physics of Ural Branch (UrD) of Russian Academy of Sciences (RAS), 620990 Ekaterinburg, Russia
| | - Igor Píš
- Elettra-Sincrotrone Trieste SCpA, S.S. 14, km 163.5, 34149 Basovizza, Trieste, Italy.,Laboratorio TASC, IOM-CNR, S.S. 14, km 163.5, 34149 Basovizza, Trieste, Italy
| | - Silvia Nappini
- Laboratorio TASC, IOM-CNR, S.S. 14, km 163.5, 34149 Basovizza, Trieste, Italy
| | - Federica Bondino
- Laboratorio TASC, IOM-CNR, S.S. 14, km 163.5, 34149 Basovizza, Trieste, Italy
| | - Ivan A Bobrikov
- Joint Institute for Nuclear Research, ul. Joliot-Curie 6, 141980 Dubna, Moscow Oblast Russia
| | - Alexander N Titov
- M. N. Miheev Institute of Metal Physics of Ural Branch (UrD) of Russian Academy of Sciences (RAS), 620990 Ekaterinburg, Russia
| |
Collapse
|
11
|
Gupta S, Kutana A, Yakobson BI. Heterobilayers of 2D materials as a platform for excitonic superfluidity. Nat Commun 2020; 11:2989. [PMID: 32533022 PMCID: PMC7293212 DOI: 10.1038/s41467-020-16737-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 05/13/2020] [Indexed: 11/12/2022] Open
Abstract
Excitonic condensate has been long-sought within bulk indirect-gap semiconductors, quantum wells, and 2D material layers, all tried as carrying media. Here, we propose intrinsically stable 2D semiconductor heterostructures with doubly-indirect overlapping bands as optimal platforms for excitonic condensation. After screening hundreds of 2D materials, we identify candidates where spontaneous excitonic condensation mediated by purely electronic interaction should occur, and hetero-pairs Sb2Te2Se/BiTeCl, Hf2N2I2/Zr2N2Cl2, and LiAlTe2/BiTeI emerge promising. Unlike monolayers, where excitonic condensation is hampered by Peierls instability, or other bilayers, where doping by applied voltage is required, rendering them essentially non-equilibrium systems, the chemically-specific heterostructures predicted here are lattice-matched, show no detrimental electronic instability, and display broken type-III gap, thus offering optimal carrier density without any gate voltages, in true-equilibrium. Predicted materials can be used to access different parts of electron-hole phase diagram, including BEC-BCS crossover, enabling tantalizing applications in superfluid transport, Josephson-like tunneling, and dissipationless charge counterflow.
Collapse
Affiliation(s)
- Sunny Gupta
- Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Alex Kutana
- Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Boris I Yakobson
- Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA.
- Department of Chemistry, Rice University, Houston, TX, 77005, USA.
- Smalley-Curl Institute for Nanoscale Science and Technology, Rice University, Houston, TX, 77005, USA.
| |
Collapse
|
12
|
Lian C, Zhang SJ, Hu SQ, Guan MX, Meng S. Ultrafast charge ordering by self-amplified exciton-phonon dynamics in TiSe 2. Nat Commun 2020; 11:43. [PMID: 31896745 PMCID: PMC6940384 DOI: 10.1038/s41467-019-13672-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Accepted: 11/14/2019] [Indexed: 11/24/2022] Open
Abstract
The origin of charge density waves (CDWs) in TiSe\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${}_{2}$$\end{document}2 has long been debated, mainly due to the difficulties in identifying the timescales of the excitonic pairing and electron–phonon coupling (EPC). Without a time-resolved and microscopic mechanism, one has to assume simultaneous appearance of CDW and periodic lattice distortions (PLD). Here, we accomplish a complete separation of ultrafast exciton and PLD dynamics and unravel their interplay in our real-time time-dependent density functional theory simulations. We find that laser pulses knock off the exciton order and induce a homogeneous bonding–antibonding transition in the initial 20 fs, then the weakened electronic order triggers ionic movements antiparallel to the original PLD. The EPC comes into play after the initial 20 fs, and the two processes mutually amplify each other leading to a complete inversion of CDW ordering. The self-amplified dynamics reproduces the evolution of band structures in agreement with photoemission experiments. Hence we resolve the key processes in the initial dynamics of CDWs that help elucidate the underlying mechanism. The physical origins of charge density waves in 1T-TiSe2 and their response to ultrafast excitation have long been a topic of theoretical and experimental debate. Here the authors present an ab initio theory that successfully captures the observed dynamics of charge density wave formation.
Collapse
Affiliation(s)
- Chao Lian
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Sheng-Jie Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Shi-Qi Hu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Meng-Xue Guan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, P. R. China.
| |
Collapse
|
13
|
Miao Z, Fan L, Xie X, Ma Y, Xue J, He T, Zha Z. Liquid Exfoliation of Atomically Thin Antimony Selenide as an Efficient Two-Dimensional Antibacterial Nanoagent. ACS APPLIED MATERIALS & INTERFACES 2019; 11:26664-26673. [PMID: 31287947 DOI: 10.1021/acsami.9b08320] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The ever-growing global crisis of multidrug-resistant bacteria has triggered a tumult of activity in the design and development of antibacterial formulations. Here, atomically thin antimony selenide nanosheets (Sb2Se3 NSs), a minimal-toxic and low-cost semiconductor material, were explored as a high-performance two-dimensional (2D) antibacterial nanoagent via a liquid exfoliation strategy integrating cryo-pretreatment and polyvinyl pyrrolidone (PVP)-assisted exfoliation. When cultured with bacteria, the obtained PVP-capped Sb2Se3 NSs exhibited intrinsic long-term antibacterial capability, probably due to the reactive oxygen species generation and sharp edge-induced membrane cutting during physical contact between bacteria and nanosheets. Upon near-infrared laser irradiation, Sb2Se3 NSs achieved short-time hyperthermia sterilization because of strong optical absorption and high photothermal conversion efficiency. By virtue of the synergistic effects of these two broad-spectrum antibacterial mechanisms, Sb2Se3 NSs exhibited high-efficiency inhibition of conventional Gram-negative Escherichia coli, Gram-positive methicillin-resistant Staphylococcus aureus, and wild bacteria from a natural water pool. Particularly, these three categories of bacteria were completely eradicated after being treated with Sb2Se3 NSs (300 μM) plus laser irradiation for only 5 min. In vivo wound healing experiment further demonstrated the high-performance antibacterial effect. In addition, Sb2Se3 NSs depicted excellent biocompatibility due to the biocompatible element constitute and bioinert PVP modification. This work enlightened that atomically thin Sb2Se3 NSs hold great promise as a broad-spectrum 2D antibacterial nanoagent for various pathogenic bacterial infections.
Collapse
Affiliation(s)
- Zhaohua Miao
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering , Hefei University of Technology , Hefei 230009 , P. R. China
- State Key Laboratory of Advanced Welding and Joining , Harbin Institute of Technology , Harbin 150001 , P. R. China
| | - Linxin Fan
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering , Hefei University of Technology , Hefei 230009 , P. R. China
| | - Xianli Xie
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering , Hefei University of Technology , Hefei 230009 , P. R. China
| | - Yan Ma
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering , Hefei University of Technology , Hefei 230009 , P. R. China
| | - Jingzhe Xue
- Department of Chemistry , University of Science and Technology of China , Hefei 230026 , P. R. China
| | - Tao He
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering , Hefei University of Technology , Hefei 230009 , P. R. China
| | - Zhengbao Zha
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering , Hefei University of Technology , Hefei 230009 , P. R. China
| |
Collapse
|
14
|
Watson MD, Clark OJ, Mazzola F, Marković I, Sunko V, Kim TK, Rossnagel K, King PDC. Orbital- and k_{z}-Selective Hybridization of Se 4p and Ti 3d States in the Charge Density Wave Phase of TiSe_{2}. PHYSICAL REVIEW LETTERS 2019; 122:076404. [PMID: 30848608 DOI: 10.1103/physrevlett.122.076404] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Indexed: 06/09/2023]
Abstract
We revisit the enduring problem of the 2×2×2 charge density wave (CDW) order in TiSe_{2}, utilizing photon energy-dependent angle-resolved photoemission spectroscopy to probe the full three-dimensional high- and low-temperature electronic structure. Our measurements demonstrate how a mismatch of dimensionality between the 3D conduction bands and the quasi-2D valence bands in this system leads to a hybridization that is strongly k_{z} dependent. While such a momentum-selective coupling can provide the energy gain required to form the CDW, we show how additional "passenger" states remain, which couple only weakly to the CDW and thus dominate the low-energy physics in the ordered phase of TiSe_{2}.
Collapse
Affiliation(s)
- Matthew D Watson
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Oliver J Clark
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Federico Mazzola
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Igor Marković
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Veronika Sunko
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Timur K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Kai Rossnagel
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
- Ruprecht-Haensel-Labor, Christian-Albrechts-Universität zu Kiel und Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Philip D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| |
Collapse
|
15
|
Fan L, Huang D, Wang Y, Miao Z, Ma Y, Zhao Q, Zha Z. Cryo-assisted exfoliation of atomically thin 2D Sb2Se3 nanosheets for photo-induced theranostics. Chem Commun (Camb) 2019; 55:2805-2808. [DOI: 10.1039/c9cc00576e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A cryo-assisted liquid exfoliation approach was developed to prepare atomically thin Sb2Se3 colloidal nanosheets for simultaneous photoacoustic imaging and photothermal therapy.
Collapse
Affiliation(s)
- Linxin Fan
- School of Food and Biological Engineering
- Hefei University of Technology
- Hefei 230009
- China
| | - Doudou Huang
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine
- School of Public Health
- Xiamen University
- Xiamen 361102
- China
| | - Yichuan Wang
- School of Food and Biological Engineering
- Hefei University of Technology
- Hefei 230009
- China
| | - Zhaohua Miao
- School of Food and Biological Engineering
- Hefei University of Technology
- Hefei 230009
- China
- State Key Laboratory of Advanced Welding and Joining
| | - Yan Ma
- School of Food and Biological Engineering
- Hefei University of Technology
- Hefei 230009
- China
| | - Qingliang Zhao
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine
- School of Public Health
- Xiamen University
- Xiamen 361102
- China
| | - Zhengbao Zha
- School of Food and Biological Engineering
- Hefei University of Technology
- Hefei 230009
- China
| |
Collapse
|
16
|
Shi J, Hong M, Zhang Z, Ji Q, Zhang Y. Physical properties and potential applications of two-dimensional metallic transition metal dichalcogenides. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.07.019] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
17
|
Chen C, Singh B, Lin H, Pereira VM. Reproduction of the Charge Density Wave Phase Diagram in 1T-TiSe_{2} Exposes its Excitonic Character. PHYSICAL REVIEW LETTERS 2018; 121:226602. [PMID: 30547625 DOI: 10.1103/physrevlett.121.226602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Indexed: 06/09/2023]
Abstract
Recent experiments suggest that excitonic degrees of freedom play an important role in precipitating the charge density wave (CDW) transition in 1T-TiSe_{2}. Through systematic calculations of the electronic and phonon spectrum based on density functional perturbation theory, we show that the predicted critical doping of the CDW phase overshoots the experimental value by 1 order of magnitude. In contrast, an independent self-consistent many-body calculation of the excitonic order parameter and renormalized band structure is able to capture the experimental phase diagram in extremely good qualitative and quantitative agreement. This demonstrates that electron-electron interactions and the excitonic instability arising from direct electron-hole coupling are pivotal to accurately describe the nature of the CDW in this system. This has important implications to understand the emergence of superconductivity within the CDW phase of this and related systems.
Collapse
Affiliation(s)
- Chuan Chen
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Physics, National University of Singapore, Singapore 117542
| | - Bahadur Singh
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Physics, National University of Singapore, Singapore 117542
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Vitor M Pereira
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Physics, National University of Singapore, Singapore 117542
| |
Collapse
|
18
|
McAvoy RL, Govoni M, Galli G. Coupling First-Principles Calculations of Electron-Electron and Electron-Phonon Scattering, and Applications to Carbon-Based Nanostructures. J Chem Theory Comput 2018; 14:6269-6275. [PMID: 30351009 DOI: 10.1021/acs.jctc.8b00728] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report first-principles calculations of electronic gaps, lifetimes, and photoelectron spectra of a series of molecules, performed by efficiently combining the computation of electron-electron and electron-phonon self-energies. The dielectric matrix is represented in terms of dielectric eigenpotentials, utilized for both the calculation of G0 W0 quasi-particle energies and the diagonalization of the dynamical matrix; virtual electronic states are never explicitly computed and all self-energies are evaluated over the full frequency spectrum. Our formulation enables electronic structure calculations at the many-body perturbation theory level, inclusive of electron-phonon coupling, for systems with hundreds of electrons.
Collapse
Affiliation(s)
- Ryan L McAvoy
- Institute for Molecular Engineering , University of Chicago , Chicago , Illinois 60637 , United States
| | - Marco Govoni
- Institute for Molecular Engineering , University of Chicago , Chicago , Illinois 60637 , United States.,Materials Science Division and Institute for Molecular Engineering , Argonne National Laboratory , Lemont , Illinois 60439 , United States
| | - Giulia Galli
- Institute for Molecular Engineering , University of Chicago , Chicago , Illinois 60637 , United States.,Materials Science Division and Institute for Molecular Engineering , Argonne National Laboratory , Lemont , Illinois 60439 , United States.,Department of Chemistry , University of Chicago , Chicago , Illinois 60637 , United States
| |
Collapse
|
19
|
Ultrafast polarization control by terahertz fields via π-electron wavefunction changes in hydrogen-bonded molecular ferroelectrics. Sci Rep 2018; 8:15014. [PMID: 30301914 PMCID: PMC6177455 DOI: 10.1038/s41598-018-33076-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 09/21/2018] [Indexed: 12/03/2022] Open
Abstract
Rapid polarization control by an electric field in ferroelectrics is important to realize high-frequency modulation of light, which has potential applications in optical communications. To achieve this, a key strategy is to use an electronic part of ferroelectric polarization. A hydrogen-bonded molecular ferroelectric, croconic acid, is a good candidate, since π-electron polarization within each molecule is theoretically predicted to play a significant role in the ferroelectric-state formation, as well as the proton displacements. Here, we show that a sub-picosecond polarization modulation is possible in croconic acid using a terahertz pulse. The terahertz-pulse-pump second-harmonic-generation-probe and optical-reflectivity-probe spectroscopy reveal that the amplitude of polarization modulation reaches 10% via the electric-field-induced modifications of π-electron wavefunctions. Moreover, the measurement of electric-field-induced changes in the infrared molecular vibrational spectrum elucidates that the contribution of proton displacements to the polarization modulation is negligibly small. These results demonstrate the electronic nature of polarization in hydrogen-bonded molecular ferroelectrics. The ultrafast polarization control via π-electron systems observed in croconic acid is expected to be possible in many other hydrogen-bonded molecular ferroelectrics and utilized for future high-speed optical-modulation devices.
Collapse
|
20
|
Han GH, Duong DL, Keum DH, Yun SJ, Lee YH. van der Waals Metallic Transition Metal Dichalcogenides. Chem Rev 2018; 118:6297-6336. [PMID: 29957928 DOI: 10.1021/acs.chemrev.7b00618] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Transition metal dichalcogenides are layered materials which are composed of transition metals and chalcogens of the group VIA in a 1:2 ratio. These layered materials have been extensively investigated over synthesis and optical and electrical properties for several decades. It can be insulators, semiconductors, or metals revealing all types of condensed matter properties from a magnetic lattice distorted to superconducting characteristics. Some of these also feature the topological manner. Instead of covering the semiconducting properties of transition metal dichalcogenides, which have been extensively revisited and reviewed elsewhere, here we present the structures of metallic transition metal dichalcogenides and their synthetic approaches for not only high-quality wafer-scale samples using conventional methods (e.g., chemical vapor transport, chemical vapor deposition) but also local small areas by a modification of the materials using Li intercalation, electron beam irradiation, light illumination, pressures, and strains. Some representative band structures of metallic transition metal dichalcogenides and their strong layer-dependence are reviewed and updated, both in theoretical calculations and experiments. In addition, we discuss the physical properties of metallic transition metal dichalcogenides such as periodic lattice distortion, magnetoresistance, superconductivity, topological insulator, and Weyl semimetal. Approaches to overcome current challenges related to these materials are also proposed.
Collapse
Affiliation(s)
- Gang Hee Han
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Dinh Loc Duong
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Dong Hoon Keum
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Seok Joon Yun
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea.,Department of Physics , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| |
Collapse
|