1
|
Tilak N, Altvater M, Hung SH, Won CJ, Li G, Kaleem T, Cheong SW, Chung CH, Jeng HT, Andrei EY. Proximity induced charge density wave in a graphene/1T-TaS 2 heterostructure. Nat Commun 2024; 15:8056. [PMID: 39277602 PMCID: PMC11401908 DOI: 10.1038/s41467-024-51608-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Accepted: 08/07/2024] [Indexed: 09/17/2024] Open
Abstract
The proximity-effect, whereby materials in contact appropriate each other's electronic-properties, is widely used to induce correlated states, such as superconductivity or magnetism, at heterostructure interfaces. Thus far however, demonstrating the existence of proximity-induced charge-density-waves (PI-CDW) proved challenging. This is due to competing effects, such as screening or co-tunneling into the parent material, that obscured its presence. Here we report the observation of a PI-CDW in a graphene layer contacted by a 1T-TaS2 substrate. Using scanning tunneling microscopy (STM) and spectroscopy (STS) together with theoretical-modeling, we show that the coexistence of a CDW with a Mott-gap in 1T-TaS2 coupled with the Dirac-dispersion of electrons in graphene, makes it possible to unambiguously demonstrate the PI-CDW by ruling out alternative interpretations. Furthermore, we find that the PI-CDW is accompanied by a reduction of the Mott gap in 1T-TaS2 and show that the mechanism underlying the PI-CDW is well-described by short-range exchange-interactions that are distinctly different from previously observed proximity effects.
Collapse
Affiliation(s)
- Nikhil Tilak
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA
| | - Michael Altvater
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA
| | - Sheng-Hsiung Hung
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
| | - Choong-Jae Won
- Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Department of Physics, Pohang University of Science and Technology, Pohang, Korea
| | - Guohong Li
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA
| | - Taha Kaleem
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA
| | - Sang-Wook Cheong
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA
| | - Chung-Hou Chung
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan.
- Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan.
- Center for Theoretical and Computational Physics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan.
| | - Horng-Tay Jeng
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
- Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan.
- Institute of Physics, Academia Sinica, Taipei, Taiwan.
| | - Eva Y Andrei
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA.
| |
Collapse
|
2
|
Tang X, Zhou J, Wong NLM, Chai J, Liu Y, Wang S, Song X. Strain-Induced Ferromagnetism in Monolayer T″-Phase VTe 2: Unveiling Magnetic States and Anisotropy for Spintronics Advancement. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:704. [PMID: 38668198 PMCID: PMC11054831 DOI: 10.3390/nano14080704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 04/14/2024] [Accepted: 04/15/2024] [Indexed: 04/29/2024]
Abstract
Two-dimensional (2D) ferromagnets have attracted significant interest for their potential in spintronic device miniaturization, especially since the discovery of ferromagnetic ordering in monolayer materials such as CrI3 and Fe3GeTe2 in 2017. This study presents a detailed investigation into the effects of the Hubbard U parameter, biaxial strain, and structural distortions on the magnetic characteristics of T″-phase VTe2. We demonstrate that setting the Hubbard U to 0 eV provides an accurate representation of the observed structural, magnetic, and electronic features for both bulk and monolayer T″-phase VTe2. The application of strain reveals two distinct ferromagnetic states in the monolayer T″-phase VTe2, each characterized by minor structural differences, but notably different magnetic moments. The T″-1 state, with reduced magnetic moments, emerges under compressive strain, while the T″-2 state, featuring increased magnetic moments, develops under tensile strain. Our analysis also compares the magnetic anisotropy between the T and T″ phases of VTe2, highlighting that the periodic lattice distortion in the T″-phase induces an in-plane anisotropy, which makes it a material with an easy-axis of magnetization. Monte Carlo simulations corroborate our findings, indicating a high Curie temperature of approximately 191 K for the T″-phase VTe2. Our research not only sheds light on the critical aspects of the VTe2 system but also suggests new pathways for enhancing low-dimensional magnetism, contributing to the advancement of spintronics and straintronics.
Collapse
Affiliation(s)
- Xiaoting Tang
- Department of Physics, College of Science, Shanghai University, 99 Shangda Road, Shanghai 200444, China;
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Jun Zhou
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore; (J.Z.); (N.L.M.W.); (J.C.)
| | - Nancy Lai Mun Wong
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore; (J.Z.); (N.L.M.W.); (J.C.)
| | - Jianwei Chai
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore; (J.Z.); (N.L.M.W.); (J.C.)
| | - Yi Liu
- Department of Physics, College of Science, Shanghai University, 99 Shangda Road, Shanghai 200444, China;
- Materials Genome Institute (MGI), Shanghai University, 333 Nanchen Road, Shanghai 200444, China
| | - Shijie Wang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore; (J.Z.); (N.L.M.W.); (J.C.)
| | | |
Collapse
|
3
|
Zhou J, Wang Z, Wang S, Feng YP, Yang M, Shen L. Coexistence of ferromagnetism and charge density waves in monolayer LaBr 2. NANOSCALE HORIZONS 2023; 8:1054-1061. [PMID: 37395097 DOI: 10.1039/d3nh00150d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Charge density waves (CDWs), a common phenomenon of periodic lattice distortions, often suppress ferromagnetism in two-dimensional (2D) materials, hindering their magnetic applications. Here, we report a novel CDW that generates 2D ferromagnetism instead of suppressing it, through the formation of interstitial anionic electrons as the charge modulation mechanism. Via first-principles calculations and a low-energy effective model, we find that the highly symmetrical monolayer LaBr2 undergoes a 2 × 1 CDW transition to a magnetic semiconducting T' phase. Concurrently, the delocalized 5d1 electrons of La in LaBr2 redistribute and accumulate within the interstitial space in the T' phase, forming anionic electrons, also known as 2D electride or electrene. The strongly localized nature of anionic electrons promotes a Mott insulating state and full spin-polarization, while the overlap of their extended tails yields ferromagnetic direct exchange between them. Such transition introduces a new magnetic form of CDWs, offering promising opportunities for exploring novel fundamental physics and advanced spintronics applications.
Collapse
Affiliation(s)
- Jun Zhou
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Zishen Wang
- Department of Physics, National University of Singapore, Singapore 117551, Singapore.
- Centre for Advanced Two-Dimensional Materials (CA2DM), National University of Singapore, Singapore 117546, Singapore
| | - Shijie Wang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Yuan Ping Feng
- Department of Physics, National University of Singapore, Singapore 117551, Singapore.
- Centre for Advanced Two-Dimensional Materials (CA2DM), National University of Singapore, Singapore 117546, Singapore
| | - Ming Yang
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
| | - Lei Shen
- Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore.
| |
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
|
Signatures of the exciton gas phase and its condensation in monolayer 1T-ZrTe 2. Nat Commun 2023; 14:1116. [PMID: 36849499 PMCID: PMC9971207 DOI: 10.1038/s41467-023-36857-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 02/16/2023] [Indexed: 03/01/2023] Open
Abstract
The excitonic insulator (EI) is a Bose-Einstein condensation (BEC) of excitons bound by electron-hole interaction in a solid, which could support high-temperature BEC transition. The material realization of EI has been challenged by the difficulty of distinguishing it from a conventional charge density wave (CDW) state. In the BEC limit, the preformed exciton gas phase is a hallmark to distinguish EI from conventional CDW, yet direct experimental evidence has been lacking. Here we report a distinct correlated phase beyond the 2×2 CDW ground state emerging in monolayer 1T-ZrTe2 and its investigation by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). The results show novel band- and energy-dependent folding behavior in a two-step process, which is the signatures of an exciton gas phase prior to its condensation into the final CDW state. Our findings provide a versatile two-dimensional platform that allows tuning of the excitonic effect.
Collapse
|
7
|
Unveiling the selenium content effect on the properties of TiSe2±α. J SOLID STATE CHEM 2022. [DOI: 10.1016/j.jssc.2022.123768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
|
8
|
Sun Z, Millis AJ. Topological Charge Pumping in Excitonic Insulators. PHYSICAL REVIEW LETTERS 2021; 126:027601. [PMID: 33512198 DOI: 10.1103/physrevlett.126.027601] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
We show that in excitonic insulators with s-wave electron-hole pairing, an applied electric field (either pulsed or static) can induce a p-wave component to the order parameter, and further drive it to rotate in the s+ip plane, realizing a Thouless charge pump. In one dimension, each cycle of rotation pumps exactly two electrons across the sample. Higher dimensional systems can be viewed as a stack of one-dimensional chains in momentum space in which each chain crossing the Fermi surface contributes a channel of charge pumping. Physics beyond the adiabatic limit, including in particular dissipative effects is discussed.
Collapse
Affiliation(s)
- Zhiyuan Sun
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
| | - Andrew J Millis
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
- Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
| |
Collapse
|
9
|
Bianco R, Monacelli L, Calandra M, Mauri F, Errea I. Weak Dimensionality Dependence and Dominant Role of Ionic Fluctuations in the Charge-Density-Wave Transition of NbSe_{2}. PHYSICAL REVIEW LETTERS 2020; 125:106101. [PMID: 32955304 DOI: 10.1103/physrevlett.125.106101] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/30/2020] [Indexed: 06/11/2023]
Abstract
Contradictory experiments have been reported about the dimensionality effect on the charge-density-wave transition in 2H 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.
Collapse
Affiliation(s)
- Raffaello Bianco
- Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia/San Sebastián, Spain
| | - Lorenzo Monacelli
- Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, I-00185 Roma, Italy
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
| | - Matteo Calandra
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
- Dipartimento di Fisica, Università di Trento, Via Sommarive 14, 38123 Povo, Italy
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252 Paris, France
| | - Francesco Mauri
- Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, I-00185 Roma, Italy
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
| | - Ion Errea
- Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia/San Sebastián, Spain
- Fisika Aplikatua 1 Saila, Gipuzkoako Ingeniaritza Eskola, University of the Basque Country (UPV/EHU), Europa Plaza 1, 20018 Donostia/San Sebastián, Spain
- Donostia International Physics Center (DIPC), Manuel Lardizabal pasealekua 4, 20018 Donostia/San Sebastián, Spain
| |
Collapse
|
10
|
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
|
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: 29] [Impact Index Per Article: 7.3] [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
|