We develop an approximation-free Diagrammatic Monte Carlo technique to study fermionic particles interacting with each other simultaneously through both an attractive Coulomb potential and bosonic excitations of the underlying medium. Exemplarily we apply the method to the long-standing exciton-polaron problem and present numerically exact results for the wave function, ground-state energy, binding energy and effective mass of this quasiparticle. Focusing on the electron-hole pair bound-state formation, we discuss various limiting cases of a generic exciton-polaron model. The frequently used instantaneous approximation to the retarded interaction due to the phonon exchange is found to be of very limited applicability. For the case of a light electron and heavy hole the system is well approximated by a particle in the field of a static attractive impurity.
We present the first approximation free diagrammatic Monte Carlo study of a lattice polaron interacting with an acoustic phonon branch through the deformation potential. Weak and strong coupling regimes are separated by a self-trapping region where quantum resonance between various possible lattice deformations is seen in the ground state properties, spectral function, and optical conductivity. The unique feature of such polaron is the interplay between long- and short wavelength acoustic vibrations creating a composite phonon cloud and leading to persistent self-trapping due to the existence …
We introduce a simple determinant diagrammatic Monte Carlo algorithm to compute the ground-state properties of a particle interacting with a Fermi sea through a zero-range interaction. The fermionic sign does not cause any fundamental problem when going to high diagram orders, and we reach order $N=30$. The data reveal that the diagrammatic series diverges exponentially as $(-1/R)^{N}$ with a radius of convergence $R<1$. Furthermore, on the polaron side of the polaron-dimeron transition, the value of $R$ is determined by a special class of three-body diagrams, corresponding to repeated scatter…
Exact theory of the finite-temperature spectral function of Fermi polarons with multiple particle-hole excitations: Diagrammatic theory versus Chevy ansatz
We consider dressing of excitonic properties by strongly correlated electrons in gate controlled twisted homo-bilayer heterostructures. The combined effect of the moiré potential and the Coulomb interaction supports the formation of different strongly correlated phases depending on the filling, including charge-ordered metals or incompressible insulators at integer occupation. The coupling between excitons and electrons results in a splitting of the excitonic resonance into an attractive and a repulsive polaron peak. Analyzing the properties of the exciton-polarons across the different phases …
Microscopic Model of Exciton Polarons in 2D Wigner Crystals
Institute for Quantum Electronics, ETH Zürich（苏黎世联邦理工学院量子电子研究所）；Institute for Theoretical Physics, ETH Zürich（苏黎世联邦理工学院理论物理研究所）；Institut für Theoretische Physik, Universität Heidelberg（海德堡大学理论物理研究所）
Purely electronic model for exciton-polaron formation in moiré heterostructures
Technical University of Munich（慕尼黑工业大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；Joint Quantum Institute, University of Maryland（马里兰大学联合量子研究所）
The effect of dispersive optical phonons on the behaviour of a Holstein polaron
本文利用无近似的Bold Diagrammatic Monte Carlo方法研究了光学声子模的有限色散对Holstein极化子性质，特别是其有效质量的影响。对于弱的电子-声子耦合，这种影响很小，但对于中等和大的电子-声子耦合，它变得显著。有效质量被发现增加（减少），如果声子色散有一个负（正）曲率在中心的布里渊区。
Exciton interacting with the phonons of an electronic Wigner crystal
Aarhus University（奥胡斯大学）；University of Copenhagen（哥本哈根大学）；University of California, Santa Barbara（加州大学圣巴巴拉分校）；Accademia di Danimarca – The Danish Academy for Science and Art in Rome（丹麦艺术与科学院）
Dispersion of low-energy optical excitations in NiPS$_3$ explained by singlet polaron theory
Instituto de Física Rosario (CONICET) and Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario（罗萨里奥物理研究所（阿根廷国家科学和技术研究委员会）及罗萨里奥国立大学精确科学、工程和测量学院）；Instituto de Nanociencia y Nanotecnología CNEA-CONICET, GAIDI, Centro Atómico Bariloche and Instituto Balseiro（CNEA-CONICET纳米科学与技术研究所、GAIDI、巴里洛切原子中心及巴尔塞罗研究所）；Physics Department, Northeastern University（东北大学物理系）
University of Maryland, College Park（马里兰大学帕克分校）；Universität Heidelberg（海德堡大学）；Laboratory for Physical Sciences（物理科学实验室）；Brookhaven National Laboratory（布鲁海文国家实验室）；National Institute for Materials Science（物质材料研究机构）
The elementary optical excitations in two dimensional semiconductors hosting itinerant electrons are attractive and repulsive polarons -- excitons that are dynamically screened by electrons. Exciton-polarons have hitherto been studied in translationally invariant degenerate Fermi systems. Here, we show that electronic charge order breaks the excitonic translational invariance and leads to a direct optical signature in the exciton-polaron spectrum. Specifically, we demonstrate that new optical resonances appear due to spatially modulated interaction between excitons and electrons in an incompre…
Spectroscopy of Wigner crystal polarons in an atomically thin semiconductor
University of Basel（巴塞尔大学）；Technical University of Munich（慕尼黑工业大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；National Institute for Materials Science（物质材料研究机构）
