arXiv subjects

Ataç İmamoğlu

Publications and source records attributed to Ataç İmamoğlu.

11 recordsLinked to original sources

arXiv2026

Correlated Metals, Metamagnetism, and Orbital Nematic Order in moiré Materials with Neural Quantum States

In this work, we investigate a continuum model of two-dimensional electrons interacting via long-range Coulomb forces and subject to a triangular periodic potential at filling factor $ν=2$. Using neural quantum states based on message-passing neural networks optimized with variational Monte Carlo, we determine the ground-state phase diagram as a function of periodic potential strength and Zeeman field. Although the noninteracting system is expected to form a conventional band insulator, we show that strong correlations can qualitatively reshape the insulating state and, in part of the phase diagram, suppress the band insulator in favor of a correlated metallic phase, with a first-order transition separating the two regimes. Moreover, the metal--insulator transition exhibits a strong dependence on spin polarization: the unpolarized system becomes insulating at substantially weaker periodic potentials through the formation of an $s$-wave molecular insulator, where opposite-spin electrons bind near each potential minimum, whereas the fully polarized system requires a significantly deeper potential and instead forms a symmetry-broken orbital nematic molecular crystal. This spin-dependent molecular transition gives rise to discontinuous magnetization curves, metamagnetic transitions, and several multicritical points in the phase diagram, together with clear signatures in the density profiles, real-space correlation functions, and structure factors. To further elucidate the role of the long-range character of the Coulomb interaction, we also study short-range repulsive interactions, which can be realized with ultracold-atom platforms. We find that the qualitative structure of the many-body phase diagram remains unchanged, demonstrating the robustness of our results across different interaction models.

cond-mat.str-el↗

arXiv2026

Interactions of electrons and Rydberg excitons in two-dimensional semiconductors

Rydberg excitons in two-dimensional semiconductors provide sensitive and non-destructive probes of physics in proximal sample layers that host correlated electronic states. In particular, electron or hole doping of the sample layer is heralded by a strong frequency shift and loss of transition strength of 2s excitons in the sensor layer. In analogy to the attractive polaron observed near the 1s exciton, this redshifted resonance, which we term Rydberg attractive polaron (RAP), has been attributed to the formation of a bound state of a 2s exciton and a remote electron. Through a theoretical analysis of exciton-electron scattering, we show that the nature of the RAP and its underlying trion can only be explained by electron-mediated hybridization of 2s, 2p and interlayer excitons, endowing the RAP a different structure than the 1s attractive polaron. We anticipate that this new understanding will ensure a more accurate assessment of the signatures of correlated electrons in two dimensional materials.

cond-mat.mes-hall↗

arXiv2026

Color Centers and Hyperbolic Phonon Polaritons in Hexagonal Boron Nitride: A New Platform for Quantum Optics

Hyperbolic phonon polaritons (HPPs) in hexagonal boron nitride (hBN) confine mid-infrared light to deep-subwavelength scales and may offer a powerful route to strong light-matter interactions. Generation and control of HPPs are typically accessed using classical near-field probes, which limits experiments at the quantum level.A complementary frontier in hBN research focuses on color centers: bright, stable, atomically localized emitters that have rapidly emerged as a promising platform for solid-state quantum optics. Here we establish a key connection between these two directions by developing a cavity-QED framework in which a single hBN color center serves as a quantum source of HPPs. We quantify the emitter-HPP interaction and analyze two generation schemes. The first is spontaneous emission into the phonon sideband, which can produce single-HPP events and, in ultrathin slabs, becomes single-mode with an enhanced decay rate. The second is a stimulated Raman process that provides frequency selectivity, tunable conversion rate, and narrowband excitation. This drive launches spatially confined, ray-like HPPs that propagate over micrometer distances. We also outline a two-emitter correlation measurement that can directly test the single-polariton character of these emissions. By connecting color-center quantum optics with hyperbolic polaritonics, our approach enables quantum emitters to act as on-chip quantum sources and controls for HPPs, while HPPs provide long-range channels that couple spatially separated emitters. Together, these capabilities point to a new direction for mid-infrared photonic experiments that unite strong coupling, spectral selectivity, and spatial reach within a single material system.

cond-mat.mes-hall↗

arXiv2025

Optical Injection and Detection of Long-Lived Interlayer Excitons in van der Waals Heterostructures

Interlayer excitons in semiconducting bilayers separated by insulating hBN layers constitute a promising platform for investigation of strongly correlated bosonic phases. Here, we report an optical method for the generation and characterization of long-lived interlayer excitons. We confirm the presence of tightly bound interlayer excitons by measuring 1s and 2s intralayer excitons in each layer concurrently. Using a pump-probe technique, we find interlayer exciton lifetimes up to 8.8 $μ$s, increasing with the thickness of the hBN. With optical access to long-lived interlayer excitons, our approach provides a new route to explore degenerate Bose--Fermi mixtures of excitons and itinerant electrons with high spatial and temporal resolution.

cond-mat.mes-hall↗

arXiv2025

Anyon-trions in atomically thin semiconductor heterostructures

The study of anyons in topologically ordered quantum systems has mainly relied on edge-state interferometry. However, realizing controlled braiding of anyons necessitates the ability to detect and manipulate individual anyons within the bulk. Here, we propose and theoretically investigate a first step toward this goal by demonstrating that a long-lived, optically generated interlayer exciton can bind to a quasihole in a fractional quantum Hall state, forming a composite excitation we term an anyon-trion. Using exact diagonalization, we show that mobile anyon-trions possess a binding energy of approximately 0.5 meV, whereas static anyon-trions exhibit a binding energy of about 0.9 meV, that is linearly proportional to the quasiholes fractional charge. An experimental realization based on photoluminescence from localized interlayer excitons in a quantum twisting microscope setup should allow for a direct optical observation of anyon-trions.

cond-mat.mes-hall↗

arXiv2025

Feshbach Resonances in Exciton-Charge-Carrier Scattering in Semiconductor Bilayers

Feshbach resonances play a vital role in the success of cold atoms investigating strongly-correlated physics. The recent observation of their solid-state analog in the scattering of holes and intralayer excitons in transition metal dichalcogenides [Schwartz et al., Science 374, 336 (2021)] holds compelling promise for bringing fully controllable interactions to the field of semiconductors. Here, we demonstrate how tunneling-induced layer hybridization can lead to the emergence of two distinct classes of Feshbach resonances in atomically thin semiconductors. Based on microscopic scattering theory we show that these two types of Feshbach resonances allow to tune interactions between electrons and both short-lived intralayer, as well as long-lived interlayer excitons. We predict the exciton-electron scattering phase shift from first principles and show that the exciton-electron coupling is fully tunable from strong to vanishing interactions. The tunability of interactions opens the avenue to explore Bose-Fermi mixtures in solid-state systems in regimes that were previously only accessible in cold atom experiments.

cond-mat.mes-hall↗

arXiv2022

Optical signatures of periodic magnetization: the moiré Zeeman effect

Detecting magnetic order at the nanoscale is of central interest for the study of quantum magnetism in general, and the emerging field of moiré magnets in particular. Here, we analyze the exciton band structure that arises from a periodic modulation of the valley Zeeman effect. Despite long-range electron-hole exchange interactions, we find a sizable splitting in the energy of the bright circularly-polarized exciton Umklapp resonances, which serves as a direct optical probe of magnetic order. We first analyze quantum moiré magnets realized by periodic ordering of electron spins in Mott-Wigner states of transition metal dichalcogenide (TMD) monolayers or twisted bilayers: we show that spin-valley dependent exciton-electron interactions allow for probing the spin-valley order of electrons and demonstrate that it is possible to observe unique signatures of ferromagnetic order in a triangular lattice and both ferromagnetic and Néel order in a honeycomb lattice. We then focus on semiclassical moiré magnets realized in twisted bilayers of ferromagnetic materials: we propose a detection scheme for moiré magnetism which is based on inter-layer exchange coupling between spins in a moiré magnet and excitons in a TMD monolayer.

cond-mat.mes-hall↗

arXiv2022

Large-bandwidth transduction between an optical single quantum-dot molecule and a superconducting resonator

Quantum transduction between the microwave and optical domains is an outstanding challenge for long-distance quantum networks based on superconducting qubits. For all transducers realized to date, the generally weak light-matter coupling does not allow high transduction efficiency, large bandwidth, and low noise simultaneously. Here we show that a large electric dipole moment of an exciton in an optically active self-assembled quantum dot molecule (QDM) efficiently couples to a microwave resonator field at a single-photon level. This allows for transduction between microwave and optical photons without coherent optical pump fields to enhance the interaction. With an on-chip device, we demonstrate a sizeable single-photon coupling strength of 16 MHz. Thanks to the fast exciton decay rate in the QDM, the transduction bandwidth between an optical and microwave resonator photon reaches several 100s of MHz.

quant-ph↗

arXiv2019

Second-order photon correlation measurement with picosecond resolution

The second-order correlation function of light $g^{(2)}(τ)$ constitutes a pivotal tool to quantify the quantum behavior of an emitter and in turn its potential for quantum information applications. The experimentally accessible time resolution of $g^{(2)}(τ)$ is usually limited by the jitter of available single photon detectors. Here, we present a versatile technique allowing to measure $g^{(2)}(τ)$ from a large variety of light signals with a time resolution given by the pulse length of a mode-locked laser. The technique is based on frequency upconversion in a nonlinear waveguide, and we analyze its properties and limitations by modeling the pulse propagation and the frequency conversion process .We measure $g^{(2)}(τ)$ from various signals including light from a quantum emitter - a confined exciton-polariton structure - revealing its quantum signatures at a scale of a few picoseconds and demonstrating the capability of the technique.

quant-ph↗

arXiv2017

Signatures of a dissipative phase transition in photon correlation measurements

Understanding and characterizing phase transitions in driven-dissipative systems constitutes a new frontier for many-body physics. A generic feature of dissipative phase transitions is a vanishing gap in the Liouvillian spectrum, which leads to long-lived deviations from the steady-state as the system is driven towards the transition. Here, we show that photon correlation measurements can be used to characterize the corresponding critical slowing down of nonequilibrium dynamics. We focus on the extensively studied phenomenon of optical bistability in GaAs cavity-polaritons, which can be described as a first-order dissipative phase transition. Increasing the excitation strength towards the bistable range results in an increasing photon-bunching signal along with a decay time that is prolonged by more than nine orders of magnitude as compared to that of low density polaritons. In the limit of strong polariton interactions leading to pronounced quantum fluctuations, the mean-field bistability threshold is washed out. Nevertheless, the scaling of the Liouvillian gap closing as thermodynamic limit is approached provides a signature of the emerging dissipative phase transition. Our results establish photon correlation measurements as an invaluable tool for studying dynamical properties of dissipative phase transitions without requiring phase-sensitive interferometric measurements.

quant-ph↗

arXiv2017

Deterministic entanglement between a propagating photon and a singlet--triplet qubit in an optically active quantum dot molecule

Two-electron charged self-assembled quantum dot molecules exhibit a decoherence-avoiding singlet-triplet qubit subspace and an efficient spin-photon interface. We demonstrate quantum entanglement between emitted photons and the spin-qubit after the emission event. We measure the overlap with a fully entangled state to be $69.5\pm2.7\,\%$, exceeding the threshold of $50\,\%$ required to prove the non-separability of the density matrix of the system. The photonic qubit is encoded in two photon states with an energy difference larger than the timing resolution of existing detectors. We devise a novel heterodyne detection method, enabling projective measurements of such photonic color qubits along any direction on the Bloch sphere.

cond-mat.mes-hall↗