Article
Chemistry, Physical
Zhao-Liang Wang, Guofu Chen, Xiaoliang Zhang, Dawei Tang
Summary: The study uses first-principles density functional theory and the phonon Boltzmann transport equation to investigate phonon transport characteristics in 1T-TiSe2. Results show that TiSe2 has extremely low lattice thermal conductivity, primarily attributed to acoustic phonons and a small portion of optical phonons, with the thermal conductivity decreasing as sample size shrinks. The high scattering rate and low group velocity result in the low thermal conductivity of the optical phonon mode in TiSe2.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
H. Saqib, S. Rahman, Yongsheng Zhao, C. Cazorla, D. Errandonea, Resta Susilo, Yukai Zhuang, Yanwei Huang, Bin Chen, Ning Dai
Summary: In TiSe2, the pressure-induced structural phase transition is closely linked to the superconducting transition, resulting in a series of phase transitions. The pressure affects the charge density wave and superconductivity significantly.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Srishti Pal, Koyendrila Debnath, Satyendra Nath Gupta, Luminita Harnagea, D. V. S. Muthu, Umesh Waghmare, A. K. Sood
Summary: The study investigates the pressure-induced structural evolution of vanadium diselenide using synchrotron-based powder x-ray diffraction and first-principles density functional theory. Anomalies in the c/a ratio, V-Se bond length, and Se-V-Se bond angle were observed at around 4 GPa, indicating an isostructural transition, followed by a first-order structural transition at around 11 GPa. Changes in the Debye-Waller factors were associated with these transitions, and spin-polarized calculations with Hubbard correction were able to capture the 1T to 3R transition with a transition pressure close to the experimental value.
Article
Materials Science, Multidisciplinary
Damien Tristant, Andrew Cupo, Ilya Vekhter, Vincent Meunier, William A. Shelton
Summary: In this study, density functional theory based ab initio calculations were used to investigate the properties of CGT. The results were in excellent agreement with experimental data, providing valuable insights for understanding and analyzing magnetic heterostructures based on CGT.
Article
Physics, Applied
Fei-Hu Liu, Wei Fu, Ying-Hua Deng, Zi-Bo Yuan, Li-Na Wu
Summary: TaTe4 is known as a CDW system with a commensurately modulated structure at room temperature. The giant Kohn anomaly in TaTe4 at room temperature is driven by a large electron-phonon coupling coefficient at the CDW vector, and can be effectively suppressed by applying hydrostatic pressure. The disappearance of CDW instability after pressure suggests that the anomaly is not caused by Fermi surface nesting.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Harshvardhan Jog, Luminita Harnagea, Dibyata Rout, Takashi Taniguchi, Kenji Watanabe, Eugene J. Mele, Ritesh Agarwal
Summary: We investigate the symmetries of 1T-TiSe2 and observe that the ground state of the CDW phase is achiral, but it can be transformed into a non-equilibrium chiral phase under high-intensity laser excitation, altering the electronic correlations in the material. The photogalvanic technique demonstrates the sensitivity to structural symmetries and provides evidence of different optically driven phases in 1T-TiSe2.
Article
Electrochemistry
J. E. Antonio, J. M. Cervantes, J. L. Rosas-Huerta, J. Pilo, E. Carvajal, R. Escamilla
Summary: This study investigated the electronic and mechanical properties of bulk TiSe2, as well as the effects of confinement into mono-, bi-, and tri-layered systems. The calculations showed that the mono-, bi-, and tri-layered systems exhibit metallic behavior similar to the bulk material. Additionally, the addition of Li atoms in monolayers may be favorable for electronic transport.
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
(2021)
Article
Chemistry, Physical
Mukhtar Lawan Adam, Hongen Zhu, Zhanfeng Liu, Shengtao Cui, Pengjun Zhang, Yi Liu, Guobin Zhang, Xiaojun Wu, Zhe Sun, Li Song
Summary: By intercalating Sn atoms, the CDW phase in 1T-TiSe2 single crystals can be gradually suppressed, inducing charge doping and modulating the intrinsic electronic properties. Temperature-dependent ARPES results reveal the role of exciton-phonon interaction and the Jahn-Teller mechanism in the formation of CDW in this material.
Article
Chemistry, Physical
Sarah Ghazanfari, Yulun Han, Wenjie Xia, Dmitri S. Kilin
Summary: A theoretical investigation was conducted on the optoelectronic properties of Fe-doped montmorillonite nanoclay under different spin states. The study revealed differences in electronic properties and nonradiative relaxation channels among low spin, intermediate spin, and high spin states. The computational results showed that the high spin state was the most stable with the largest Fe-O distances. Different nonradiative relaxation pathways were observed for electrons and holes.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Physics, Multidisciplinary
Q. Hu, J. Y. Liu, Q. Shi, F. J. Zhang, Y. Zhong, L. Lei, R. Ang
Summary: Understanding the interplay between superconductivity and charge-density wave (CDW) in transition-metal dichalcogenides (TMDs) is of fundamental interest in scientific research and applications. This study investigated the physical mechanism of superconducting transition in Ta-doped 1T-Ti1-xTaxSe2 single crystals through density functional theory (DFT) calculations and experiments. The results suggest that CDW suppression and enhancement of density of states near the Fermi level contribute to the emergence of superconductivity within the CDW phase, offering insights for potential electronic device applications.
Article
Materials Science, Multidisciplinary
Turgut Yilmaz, Elio Vescovo
Summary: Low-temperature, high-resolution angle resolved photoemission experiments on bulk 1T-TiSe2 samples reveal conspicuous band folding as the only prominent signature of the periodic lattice distortion. No confirmation of a bulk electronic gap supporting a charge density wave phase is found in light of the new data. These observations cast serious doubts on the common belief of an electronic instability as the likely origin for the observed structural transition in TiSe2.
Article
Physics, Multidisciplinary
Shin-Ming Huang, Su-Yang Xu, Bahadur Singh, Ming-Chien Hsu, Chuang-Han Hsu, Chenliang Su, Arun Bansil, Hsin Lin
Summary: By using first-principles computations within the framework of density functional theory, this study reveals the connection between the symmetries of normal and CDW states and the electronic structure of 1T-TiSe2, emphasizing the crucial role of irreducible representations of electronic states and band gaps in driving the formation of CDW. The research demonstrates how symmetry-related topology can be directly obtained from the electronic structure, providing a practical pathway in the search for topological CDW insulators.
NEW JOURNAL OF PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Hanjing Zhou, Songsong Yan, Dongze Fan, Di Wang, Xiangang Wan
Summary: In this study, the electronic structure, magnetic properties, and possible structural distortion of FeGe are comprehensively investigated using density functional theory and symmetry analysis. The dominant magnetic interaction is found to be the ferromagnetic nearest-neighbor J1, while the magnetic interactions between nearest kagome layers favors antiferromagnetic. The presence of DM interactions can result in the small magnetic cone angle observed.
Article
Physics, Multidisciplinary
Ming-Chien Hsu, Bahadur Singh, Chuang-Han Hsu, Su-Yang Xu, Hsin Lin, Shin-Ming Huang
Summary: CDW can change the symmetry and electronic structure of a system, leading to possible band inversion and offering a chance for topological phase transition. Monolayer 1T-TiSe2 was found to exhibit an unconventional CDW phase with a triple-q M-1(-) structure, which also results in a small M-1(+) CDW.
NEW JOURNAL OF PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Jianjun Wang, Lin Li, Jiudong Wang, Wentao Yang, Peng Guo, Meng Li, Dandan Liu, Haoxian Zeng, Bin Zhao
Summary: This study investigates the friction properties of hydrogenated and fluorinated diamane for the first time using dispersion-corrected DFT calculations. Results show that fluorinated diamane exhibits similar friction to graphene, while hydrogenated diamane has a friction coefficient twice that of fluorinated diamane. This is attributed to the charge-packed surface of fluorinated diamane.
Article
Materials Science, Multidisciplinary
Giovanni Marini, Matteo Calandra
Summary: Superconductivity is observed in electrochemically doped molybdenum dichalcogenides samples thicker than four layers. The critical temperature (T(c)) depends strongly on the field effect geometry (single or double gate) and the sample (MoS2 or MoSe2), but always saturates at high doping levels. The mechanisms behind the pairing and the intricate dependence of T(c) on doping, samples, and field-effect geometry are still unknown.
Article
Physics, Multidisciplinary
Lorenzo Monacelli, Michele Casula, Kousuke Nakano, Sandro Sorella, Francesco Mauri
Summary: Modeling hydrogen at high pressures and low temperatures is challenging due to significant quantum effects. This study uses advanced methods to calculate the phase diagram of hydrogen and deuterium, revealing a metallic hydrogen phase that could host room-temperature superconductivity.
Article
Physics, Multidisciplinary
Tommaso Venanzi, Lorenzo Graziotto, Francesco Macheda, Simone Sotgiu, Taoufiq Ouaj, Elena Stellino, Claudia Fasolato, Paolo Postorino, Vaidotas Miseikis, Marvin Metzelaars, Paul Koegerler, Bernd Beschoten, Camilla Coletti, Stefano Roddaro, Matteo Calandra, Michele Ortolani, Christoph Stampfer, Francesco Mauri, Leonetta Baldassarre
Summary: We performed resonance Raman spectroscopy measurements on graphene with excitation photon energy as low as 1.16 eV to investigate the interaction between low-energy carriers and lattice vibrations. By utilizing excitation energy close to the Dirac point at K, we observed a significant increase in the intensity ratio between the double-resonant 2D and 2D' peaks compared to graphite. Through theoretical calculations, we determined that this observation is attributed to an enhanced, momentum-dependent coupling between electrons and Brillouin zone-boundary optical phonons, which has implications for modeling transport in graphene devices operating at room temperature.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Physical
Michele Simoncelli, Francesco Mauri, Nicola Marzari
Summary: Predicting the thermal conductivity of glasses from first principles has been a complex problem, as previous approaches neglect anharmonicity and quantum statistics of vibrations. In this study, the authors present a protocol that combines the Wigner formulation of thermal transport with convergence-acceleration techniques to determine the thermal conductivity of glasses. They validate this approach in vitreous silica and discuss the effects of anharmonicity and the mechanisms determining the trend of thermal conductivity at high temperature.
NPJ COMPUTATIONAL MATERIALS
(2023)
Article
Quantum Science & Technology
Luigi Ranalli, Carla Verdi, Lorenzo Monacelli, Georg Kresse, Matteo Calandra, Cesare Franchini
Summary: This study combines density functional theory calculations with a machine-learned force field method to investigate the quantum paraelectric state in the quantum ferroelectric material KTaO3. The results demonstrate the importance of including anharmonic terms to stabilize the spurious imaginary ferroelectric phonon predicted by DFT in the harmonic approximation, in agreement with experiments. This work proposes a robust computational workflow capable of accounting for collective behaviors involving different degrees of freedom and occurring at large time/length scales, paving the way for precise modeling and control of quantum effects in materials.
ADVANCED QUANTUM TECHNOLOGIES
(2023)
Article
Chemistry, Physical
Stefano Mocatti, Giovanni Marini, Matteo Calandra
Summary: Using constrained density functional perturbation theory and considering light-induced quantum anharmonicity, we have achieved a first-order nonthermal phase transition from the topologically trivial orthorhombic structure of SnSe to the topological crystalline insulating rocksalt phase. We have described the reaction path and evaluated the critical fluence and possible decay channels after photoexcitation.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Ludovica Zullo, Giovanni Marini, Tristan Cren, Matteo Calandra
Summary: In this study, the charge transfer mechanism of misfit compounds is revealed by performing first-principles calculations. It is discovered that rocksalt units always act as donors, while transition metal dichalcogenides act as acceptors. The interaction between the rocksalt units and other components enables ultra-high charge control of up to 6×10^14 e(-) cm(-2). Additionally, a strategy for designing emergent superconductivity is identified and successfully applied in (LaSe)(1.27)(SnSe2)(2). This work lays the foundation for synthesizing misfit compounds with tailored physical properties.
Review
Nanoscience & Nanotechnology
Vladislav O. Khaustov, Domenica Convertino, Janis Koester, Alexei A. Zakharov, Michael J. Mohn, Zewdu M. Gebeyehu, Leonardo Martini, Simona Pace, Giovanni Marini, Matteo Calandra, Ute Kaiser, Stiven Forti, Camilla Coletti
Summary: This study reports a phase transition from the 1H phase to the 1T' phase in single-layer molybdenum ditelluride (MoTe2) during the chemical vapor deposition (CVD) synthesis process. The transformation is caused by the heterocontact between monoclinic and hexagonal crystals. The understanding and control of the direct synthesis of lateral 1T'/1H heterostructures contribute to the development of MoTe2-based electronic and optoelectronic devices with low contact resistance.
ACS APPLIED NANO MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Antonio Siciliano, Lorenzo Monacelli, Giovanni Caldarelli, Francesco Mauri
Summary: In this paper, the authors propose a time-dependent self-consistent harmonic approximation (TDSCHA) method in the Wigner framework for efficient computation of nuclear motion in systems with quantum and thermal anharmonic fluctuations. The method can account for nonlinear couplings between phonons and photons, and can be used in unsupervised high-throughput calculations.
Article
Materials Science, Multidisciplinary
Francesco Macheda, Thibault Sohier, Paolo Barone, Francesco Mauri
Summary: Studies show that the electron-phonon interaction and phonon frequencies of doped polar semiconductors are highly sensitive to long-range Coulomb forces and screening effects of free carriers. A linear-response dielectric-matrix formalism is used to properly account for these screening effects, allowing for controlled approximations. Computational methods have been proposed to evaluate effective charges and the static dielectric function of doped two-dimensional semiconductors from first principles. Results suggest that doping in disproportionated graphene leads to a significant reduction in optical Frohlich and acoustic piezoelectric couplings, as well as the slope of optical longitudinal modes.
Article
Materials Science, Multidisciplinary
C. Tresca, T. Bilgeri, G. Menard, V. Cherkez, R. Federicci, D. Longo, M. Herve, F. Debontridder, P. David, D. Roditchev, G. Profeta, T. Cren, M. Calandra, C. Brun
Summary: In this paper, we address the general issues in extracting local charge order from STM/STS measurements in two-dimensional systems. We demonstrate that the widely used lock-in technique cannot be used to accurately extract the local charge order in cases where there are spatial variations and energy dependencies. Instead, we propose either performing constant height measurements or a full grid of dI/dV(V) spectroscopies to obtain more reliable results.
Article
Materials Science, Multidisciplinary
Davide Romanin, Matteo Calandra
Summary: The study investigates the impact of nuclear quantum effects on the stability, vibrational, and optical properties of cyclo[4n + 2]carbons. It reveals that quantum anharmonic effects play a significant role in altering energy differences between isomers and reshaping optical absorbance.
Article
Materials Science, Multidisciplinary
Giovanni Caldarelli, Michele Simoncelli, Nicola Marzari, Francesco Mauri, Lara Benfatto
Summary: Recent progress in understanding thermal transport in complex crystals has highlighted the important role of heat conduction mediated by interband tunneling processes. The differences in describing these processes using the Wigner or Green-Kubo formalism have raised questions about the definition of the heat-current operator. In this study, a full quantum approach based on the Kubo formula is implemented to investigate thermal transport in the overdamped regime of atomic vibrations. The numerical comparison of thermal conductivity obtained using first-principles calculations shows that the differences between the aforementioned approaches are negligible for practical applications in the quasiparticle regime.
Article
Materials Science, Multidisciplinary
Jean Paul Nery, Francesco Mauri
Summary: This paper introduces a stochastic method for evaluating the nonperturbative interacting Green's function in the adiabatic limit, showing its equivalence to the Feynman expansion to all orders in the perturbation. By defining a self-energy, the broadening effect in numerical calculations can be reduced. The study reveals significant differences between second-order perturbation theory and nonperturbative changes at high temperatures, and the asymmetry of the spectral function increases at stronger coupling and higher temperatures.
Article
Materials Science, Multidisciplinary
Matteo Barborini, Matteo Calandra, Francesco Mauri, Ludger Wirtz, Pierluigi Cudazzo
Summary: This work investigates the purely electronic instability in one-dimensional semimetals independent of a lattice distortion by accurate ab initio calculations on one-dimensional carbon chain and monatomic hydrogen chain based on quantum Monte Carlo and hybrid density functional theory.
