Article
Chemistry, Physical
Chenjing Quan, Xiao Xing, Tingyuan Jia, Zeyu Zhang, Chunwei Wang, Sihao Huang, Zhengzheng Liu, Juan Du, Yuxin Leng
Summary: The charge transfer process in two-dimensional graphene/transition metal dichalcogenides heterostructures was investigated. The study revealed the correlation between the hot phonon bottleneck effect in graphene and the charge transfer process. The existence of interlayer charge transfer in the heterostructure and its dependence on pump fluence were confirmed.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Physical
Chenjing Quan, Xiao Xing, Tingyuan Jia, Zeyu Zhang, Chunwei Wang, Sihao Huang, Zhengzheng Liu, Juan Du, Yuxin Leng
Summary: In this study, the hot carrier transport in graphene/transition metal dichalcogenides heterostructures was investigated using optical pump and terahertz probe spectroscopy. The results revealed the relationship between charge transfer and pump fluence, providing insights into the mechanism for further exploration of optoelectronic devices.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Multidisciplinary Sciences
Mir Mohammad Sadeghi, Yajie Huang, Chao Lian, Feliciano Giustino, Emanuel Tutuc, Allan H. MacDonald, Takashi Taniguchi, Kenji Watanabe, Li Shi
Summary: The peculiar electron-phonon interaction in graphene heterostructures enables ultrahigh mobility, electron hydrodynamics, superconductivity, and superfluidity. A peak in the Lorenz ratio near 60 kelvin and its decrease with increased mobility are observed in degenerate graphene, indicating an unusual behavior. This experimental observation, combined with ab initio calculations and analytical models, suggests that broken reflection symmetry in graphene heterostructures can relax the selection rule for electron coupling with flexural phonons, contributing to the increase of the Lorenz ratio at intermediate temperatures.
Article
Chemistry, Physical
Dipti Jasrasaria, Eran Rabani
Summary: Nonradiative processes control the efficiencies of semiconductor nanocrystal-based devices, and hot exciton cooling is a central process in which highly excited electron/hole pairs relax to form band-edge excitons through nonradiative means. However, the timescale and mechanism of cooling in nanocrystals are not well understood due to quantum confinement effects. Experimental measurements of the cooling timescale range six orders of magnitude.
NPJ COMPUTATIONAL MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Te-Huan Liu, Jiawei Zhou, Qian Xu, Xin Qian, Bai Song, Ronggui Yang
Summary: The study shows that long-range electron-phonon interaction can significantly suppress thermal conductivity in certain polar semiconductors by scattering acoustic phonons. The breaking of centrosymmetry has different effects on phonon transport in different crystal structures.
MATERIALS TODAY PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Megan A. Steves, Siavash Rajabpour, Ke Wang, Chengye Dong, Wen He, Su Ying Quek, Joshua A. Robinson, Kenneth L. Knappenberger
Summary: The study on the electron dynamics of atomically thin 2-D polar metal heterostructures revealed rapid carrier transfer between metals and graphene components, as well as consecutive cooling mechanisms and accelerated electron-phonon scattering rates in alloys. The research suggests that energy dissipation rates can be tuned through atomic-level structures.
Article
Chemistry, Physical
Carolina Villamil Franco, Gaelle Trippe-Allard, Benoit Mahler, Christian Cornaggia, Jean-Sebastien Lauret, Thomas Gustavsson, Elsa Cassette
Summary: Investigated the exciton relaxation dynamics in strongly confined lead iodide perovskite nanoplatelets, finding a fast hot exciton relaxation process and a hot phonon bottleneck effect. Results suggest a role of the surface ligands in the cooling process.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Qi Liu, Xianyang Lu, Yuxiang Liu, Zhihao Li, Pengfei Yan, Wang Chen, Qinghao Meng, Yongheng Zhang, ChiYung Yam, Liang He, Yu Yan, Yi Zhang, Jing Wu, Thomas Frauenheim, Rong Zhang, Yongbing Xu
Summary: By introducing different contents of Bi adatoms to the surface of monolayer graphene, the carrier concentration and their dynamics have been effectively modulated as probed directly by the time- and angle-resolved photoemission spectroscopy technique. The Bi adatoms are found to assist acoustic phonon scattering events mediated by supercollisions as the disorder effectively relaxes the momentum conservation constraint. A reduced carrier multiplication has been observed, which is related to the shrinking Fermi sea for scattering, as confirmed by time-dependent density functional theory simulation. This work gives insight into hot carrier dynamics in graphene, which is crucial for promoting the application of photoelectric devices.
Article
Chemistry, Multidisciplinary
Marten Duvel, Marco Merboldt, Jan Philipp Bange, Hannah Strauch, Michael Stellbrink, Klaus Pierz, Hans Werner Schumacher, Davood Momeni, Daniel Steil, G. S. Matthijs Jansen, Sabine Steil, Dino Novko, Stefan Mathias, Marcel Reutzel
Summary: This study investigates far-from-equilibrium many-body interactions using photoelectron spectroscopy and finds remarkable transient renormalizations of the quasiparticle self-energy due to non-equilibrium conditions. These observations can be explained by ultrafast scatterings between nonequilibrium electrons and strongly coupled optical phonons.
Article
Materials Science, Multidisciplinary
X. Yang, A. Jena, F. Meng, S. Wen, J. Ma, X. Li, W. Li
Summary: In this study, the effect of electron-phonon interaction on the lattice thermal conductivity of graphene was investigated using first-principles calculations. It was found that the indirect coupling between flexural acoustic phonons and electrons has a significant impact on thermal conductivity in graphene, particularly due to the dominance of normal processes. Additionally, an unusual minimum thermal conductivity was observed at a specific charge carrier density in graphene.
MATERIALS TODAY PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Andreij C. Gadelha, Viet-Hung Nguyen, Eliel G. S. Neto, Fabiano Santana, Markus B. Raschke, Michael Lamparski, Vincent Meunier, Jean-Christophe Charlier, Ado Jorio
Summary: This study investigates the importance of phonons in twisted-bilayer graphene at the magic-angle using gate-dependent micro-Raman spectroscopy. The results reveal that the unique electronic structure at the magic-angle influences the electron-phonon coupling, resulting in a larger G band line width.
Article
Physics, Condensed Matter
O. Herrfurth, E. Krueger, S. Blaurock, H. Krautscheid, M. Grundmann
Summary: Simulation of carrier and lattice relaxation after optical excitation was conducted for wide-bandgap semiconductors CuI and ZnO. Transient temperature dynamics of electrons, holes, and various phonon modes were studied, confirming the importance of carrier-LO-phonon interaction and hot-phonon effects. The results supported recent findings from time-resolved optical spectroscopy experiments.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Chemistry, Multidisciplinary
Yocefu Hattori, Jie Meng, Kaibo Zheng, Ageo Meier de Andrade, Jolla Kullgren, Peter Broqvist, Peter Nordlander, Jacinto Sa
Summary: By adjusting the operating temperature, the hot electron generation and transfer in plasmonic semiconductor materials can be optimized, contrasting with photodriven processes in nonplasmonic systems. This effect appears to be related to an enhancement in hot carrier generation due to phonon coupling. This discovery provides a new strategy for the optimization of photodriven energy production and chemical synthesis.
Article
Chemistry, Physical
Jiwon Jeon, Youngjae Kim, J. D. Lee
Summary: Pseudospin, a fundamental quantum number in graphene, can be changed by the rotation of phonons. By observing the phonon satellite accompanying the linearly pumped electron to the upper Dirac cone, we found that pseudospin exhibits rotation, nonzero angular momentum, and Berry curvature. We also identified the phonon responsible for pseudospin rotation as an elliptically polarized phonon, which can induce chiral phonon excitation without circularly polarized pumping.
Article
Chemistry, Multidisciplinary
Bin Cao, Tobias Grass, Olivier Gazzano, Kishan Ashokbhai Patel, Jiuning Hu, Markus Muller, Tobias Huber-Loyola, Luca Anzi, Kenji Watanabe, Takashi Taniguchi, David B. Newell, Michael Gullans, Roman Sordan, Mohammad Hafezi, Glenn S. Solomon
Summary: By accurately measuring the photocurrent signal and modeling the data using optical Bloch equations, we have studied the relaxation of carriers in graphene in the quantum Hall regime. Our results provide a unified understanding of the relaxation processes in graphene over different magnetic field strength regimes and show clear evidence of carrier multiplication. Additionally, our findings reveal the interplay of Coulomb interactions and interactions with acoustic and optical phonons, as well as the chiral transport properties and chirality change at the Dirac point in the quantum Hall regime.
Article
Physics, Multidisciplinary
Sankar Das Sarma
Summary: Majorana particles, which are the same as their antiparticles, show promise for quantum computing in condensed matter systems. This article discusses the search for Majorana modes in semiconductor heterostructures and the limitations imposed by disorder. Majorana zero modes are emergent phenomena in topological superconductors, and this Perspective provides an overview of their physics, recent experimental progress, and future outlook for success.
Article
Physics, Multidisciplinary
DinhDuy Vu, Sankar Das Sarma
Summary: An ergodic system subjected to an external periodic drive will be heated to infinite temperature, but this heating can be stopped during a prethermal period if the applied frequency is larger than the typical energy scale of the local Hamiltonian. This prethermal period exhibits an emergent symmetry that, if broken, leads to subharmonic oscillation of the discrete time crystal (DTC). The presence of dissipation affects the survival time of the prethermal DTC, with a bath coupling prolonging the prethermal period and interaction with the environment destabilizing spontaneous symmetry breaking, resulting in a nonmonotonic variation of the survival time.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Jiabin Yu, Ming Xie, Fengcheng Wu, Sankar Das Sarma
Summary: Signatures of nematic nodal superconductivity have been observed in magic angle twisted bilayer graphene. Researchers propose a general topological mechanism explaining how nematic pairing leads to nodal superconductivity in this material.
Article
Materials Science, Multidisciplinary
Prathyush P. Poduval, Sankar Das Sarma
Summary: We theoretically investigate the issue of doping induced insulator to metal transition in bulk semiconductors by analyzing the density-dependent mean free path and the Anderson localization transition controlled by the Ioffe-Regel-Mott (IRM) criterion. We calculate the mean free path on the highly doped metallic side considering carrier scattering by ionized dopants. The Coulomb disorder of the charged dopants is screened by the carriers themselves, leading to an integral equation for localization. By solving this equation analytically and numerically, we provide detailed results for the critical density of the doping induced metal-insulator transition.
Article
Materials Science, Multidisciplinary
Nathan L. Foulk, Sankar Das Sarma
Summary: We demonstrate the potential realization of quantum Floquet matter, particularly the discrete time crystal (DTC), using modern silicon spin qubits based in quantum dots. This is significant as silicon spin qubits have advantages in dealing with charge noise. We show the differences between prethermal phenomena and true time-crystalline spatiotemporal order, and illustrate rich regime structures in a spin chain of four qubits that are distinct from the thermal regime.
Article
Materials Science, Multidisciplinary
Seth M. Davis, Yang-Zhi Chou, Fengcheng Wu, Sankar Das Sarma
Summary: We calculate the theoretical contribution of scattering by acoustic phonons to the doping and temperature dependence of electrical resistivity in Bernal bilayer graphene (BBG) and rhombohedral trilayer graphene (RTG). The nontrivial geometric features of the band structures of these systems strongly influence the resistivity's temperature and doping dependencies. Our focus on BBG and RTG is motivated by recent experiments in these systems that have discovered exotic low-temperature superconductivity. The understanding of the influence of band geometry on transport is crucial in these systems.
Article
Materials Science, Multidisciplinary
Haining Pan, Sankar Das Sarma
Summary: Motivated by the presence of Majorana zero modes in both the Kitaev chain model and the experimental semiconductor-superconductor Majorana nanowire, this theoretical study investigates the equivalence or similarity between the two models from the perspective of their corresponding dual spin models. By using the Jordan-Wigner transformation, the duality between the Kitaev chain and the transverse-field XY spin model is established, aiming to connect the Kitaev chain and the nanowire. The application of the Jordan-Wigner transformation to the nanowire reveals that the corresponding bosonic spin model is a generalized spin cluster model with staggered couplings. By projecting out the higher energy band of the spinful nanowire system, an effective low-energy spinless system is obtained, leading to the connection between the Kitaev chain and Majorana nanowire.
Article
Materials Science, Multidisciplinary
Yi-Ting Tu, Sankar Das Sarma
Summary: We analyze an experimental work which shows the failure of the Wiedemann-Franz law in graphene at low temperatures, attributing this failure to the non-Fermi liquid nature of the Dirac fluid. Despite theoretical efforts, the observations remain unexplained. Our analysis suggests that the opening of a gap at the Dirac point induced by the substrate may explain the results. Further experiments are needed to resolve the issue and determine the role of electron and hole transport in the presence of disorder and phonons.
Article
Materials Science, Multidisciplinary
Yi-Ting Tu, DinhDuy Vu, S. Das Sarma
Summary: Coupling a one-dimensional quasiperiodic interacting system to a Markovian bath, this study investigates the avalanche instability of the many-body localized phase numerically. The results show that many-body localization (MBL) is more stable in pseudorandom quasiperiodic systems than in randomly disordered systems for a disorder strength W > 8, potentially up to arbitrarily large system sizes. Real-space RG arguments support this conclusion and a detailed comparison between quasiperiodic and random MBL from the avalanche instability perspective reveals that they belong to different universality classes.
Article
Materials Science, Multidisciplinary
Donovan Buterakos, Sankar Das Sarma
Summary: We discuss interesting phenomena in the Hubbard model related to flat-band ferromagnetism. The first is a mathematical theorem that describes the conditions for degeneracy between a flat-band ferromagnetic and a nonferromagnetic state. This theorem is generally applicable and independent of geometry, but only holds for a small number of holes in a filled band. The second phenomenon challenges intuition by showing an example where particles do not prefer to doubly occupy low-energy states before filling higher-energy states. Lastly, we present a pattern of ferromagnetism in small pentagonal and hexagonal plaquettes at specific filling factors. These examples can be observed in quantum dot arrays available in laboratories.
Article
Materials Science, Multidisciplinary
Yang-Zhi Chou, Fengcheng Wu, Jay D. Sau, Sankar Das Sarma
Summary: We investigate the competition between acoustic phonon mediated superconductivity and the long-range Coulomb interaction in moireless graphene multilayers. Our theory explains recent experimental findings in Bernal bilayer graphene and rhombohedral trilayer graphene, and predicts the existence of superconductivity in ABCA tetralayer graphene. The inclusion of realistic band structures with Van Hove singularities and Coulomb repulsion effects in our theory is crucial. Our work provides detailed predictions for graphene superconductivity induced by electron-acoustic phonon interaction, which should be investigated in future experiments.
Article
Materials Science, Multidisciplinary
Robert E. Throckmorton, S. Das Sarma
Summary: This study determines the decoherence time in a system of exchange-coupled electronic spin qubits by calculating the return probability. The multiqubit geometry is found to play a crucial role in the decoherence time.
Article
Materials Science, Multidisciplinary
Seongjin Ahn, Sankar Das Sarma
Summary: This theoretical study validates the experimentally observed sudden change in 2D resistivity with a spontaneous valley polarization transition from 2 to 1 at the critical density, showing quantitative consistency between the two.
Article
Materials Science, Multidisciplinary
Haining Pan, Sankar Das Sarma
Summary: Motivated by recent experiments, this study proposes an alternative mechanism through theoretical simulations to explain the generation of large zero-bias conductance peaks in Majorana nanowires. The mechanism includes three conditions: strong potential disorder in the nanowire bulk, suppression of disorder near the wire ends, and low tunnel barrier strength. These conditions are often satisfied in experiments, thereby explaining the observed large zero-bias conductance peaks.
Article
Materials Science, Multidisciplinary
Jiabin Yu, Yu-An Chen, Sankar Das Sarma
Summary: This study generalizes the topologically obstructed pairings between Chern states by proposing Euler obstructed Cooper pairing in 3D systems. The Euler obstructed pairing widely exists between two Fermi surfaces with nontrivial band topology and can lead to nodal superconductivity and hinge Majorana zero modes under certain conditions.
