Mesoscale and Nanoscale Physics
Tunable g-Factors of Hybridized Orbitals in a Quantum Dot Molecule
Michelle Lienhart, Krzysztof Gawarecki, Pavel Daskalov et al. (+10 more)
The ability to control the $g$-factors of orbital
spin states in optically active
quantum dot molecules (QDMs) is a prerequisite for the high-fidelity generation of multi-photonic cluster states with higher-dimensional
entanglement structure. Protocols that rely on two coupled
spins require knowledge of the $g$-factor and its dependence on external control parameters. Mismatches in the $g$-factor between tunnel-coupled dots introduce unwanted dephasing of coupled
spin-states, making precise characterization and voltage control essential. Here, we measure the gate voltage dependence of the electron and hole $g$-factors of negatively charged trions $X^{-}$ in a single InGaAs QDM using polarization-resolved magneto-photoluminescence spectroscopy. The electron $g$-factor exhibits a pronounced step-like change at the tunneling resonance, shifting from $g_\mathrm{e} = -0.336\pm 0.008$ to $g_\mathrm{e} = -0.389\pm 0.003$, providing a direct spectroscopic fingerprint of molecular orbital formation and a shift of the wavefunction localization from the lower to the upper dot. In contrast, the hole $g$-factor remains nearly constant at $g_\mathrm{h} \approx 0.094 \pm 0.007$, exhibiting a weak modulation near the anticrossing voltages attributed to Coulomb-mediated deformation of the wavefunction by the tunneling electron. Our results are quantitatively reproduced by an eight-band $\mathbf{k}{\cdot}\mathbf{p}$ model, establishing electric-field control of the trion $g$-factors as a practical tool for independently tuning the Zeeman splitting of individual dots and opening new pathways towards the deterministic generation of two-dimensional photonic cluster states.
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All authors Michelle Lienhart, Krzysztof Gawarecki, Pavel Daskalov, Christopher Thalacker, Nadeem Akhlaq, Irina Ivanova, Johannes Schall, Sven Rodt, Stephan Reitzenstein, Arne Ludwig, Dirk Reuter, Kai Müller, Jonathan J. Finley
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.mtrl-sci
Extracting the full conductivity tensor in a rectangular sample
Julia Gelfond and Oskar Vafek
Electrical transport measurements reveal that many 2D materials exhibit anisotropic conductivity. However, current methodologies for rectangular geometries can only extract a partial conductivity tensor or are difficult to execute experimentally. Here, we propose a simple experimental procedure to extract the full conductivity tensor (or the resistivity tensor by inversion) including the principal axes angle. Our procedure is developed by using a conformal mapping approach to obtain an analytical expression for the potential with a point source and drain on the perimeter. Our solution agrees very well with numerical simulations using COMSOL and the known limiting case where the principal axes angle vanishes. Finite source/drains can be modeled using superposition.
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Mesoscale and Nanoscale Physics
Observation of metastable chiral domain walls in a topological magnet
Richen Xiong, Chenxin Qin, Zhaoyu Han et al. (+17 more)
The interplay between
topology and correlation can give rise to exotic collective excitations. The integer and fractional
quantum anomalous Hall (QAH) magnets recently discovered in two-dimensional (2D) flatband systems are predicted to host
spin excitations distinct from those in conventional magnets. Experimentally, nevertheless, these new excitations remain largely unexplored. Here we investigate
spin-valley excitations in a twisted MoTe2 moiré superlattice using resonant ultrafast pump-probe spectroscopy. We observe a metastable
spin-valley excitation in the QAH magnet below T ~ 3.7 K that survives reverse
magnetic field several times larger than the saturation field. The behavior of this excitation is sharply distinct from ordinary domain walls and
magnons, indicating a new type of
spin-valley textures unique to topological magnets. We propose that these textures are chiral domain walls with an in-plane winding of the pseudospin order parameter along the domain wall. Their metastability arises from the interplay between the topological winding in real space and the
quantum geometry of the parent bands in momentum space through a universal mechanism. These chiral domain walls govern the nonequilibrium dynamics of QAH magnets and may play a central role in their stability. Our study highlights intrinsic
quantum geometry effects on
spin excitations in topological magnets; and provides key insights into the fundamental mechanism limiting stability of topological protection.
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All authors Richen Xiong, Chenxin Qin, Zhaoyu Han, Nisarg Chadha, Qiang Gao, William Holtzmann, Weijie Li, Jiaqi Cai, Yi Guo, Weihanzhang Guo, Qi Chen, Samuel L. Brantly, Sam Bonkowsky, Chen Huang, Kenji Watanabe, Takashi Taniguchi, Andrea F. Young, Xiaodong Xu, Eslam Khalaf, Chenhao Jin
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.mtrl-sci
Nonreciprocity reversal of magnetoacoustic attenuation in NiFe alloy thin films
Mingran Xu, Kei Yamamoto, Kouta Kondou et al. (+8 more)
Nonreciprocity, the asymmetry of transport, underlies technologies from the diode to the microwave isolator. In a ferromagnet, a surface acoustic wave generates an elliptical effective field with propagation-locked handedness, breaking the reciprocity of its propagation. Despite decades of study on this phenomenon, a method for controlling the sign of the nonreciprocity has remained elusive. Here we observe a sign reversal in Ni$_x$Fe$_{100-x}$ films. A 0.8 at.% change across Permalloy's zero-magnetostriction composition, where the magnetoelastic coefficient $b$ changes sign, reverses the handedness of the elliptical effective field and thereby the nonreciprocity, from 78.6% to -61.8%. Angle-dependent measurements and
spin-wave-ellipticity modelling show that reversing the sign of $b$ reverses the handedness of the elliptically polarized effective field. Aided by cubic frequency scaling, we resolve the sign of $b$ down to -0.05 MPa in a 10-nm film, establishing nonreciprocity as a nanoscale probe of magnetoelastic coupling.
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All authors Mingran Xu, Kei Yamamoto, Kouta Kondou, Zheng Zhu, Liyang Liao, Kiyohiro Adachi, Tomoka Kikitsu, Daisuke Hashizume, Dirk Grundler, Sadamichi Maekawa, Yoshichika Otani
Mesoscale and Nanoscale Physics
Temperature-tunable spin-wave refraction using superconducting control elements
Pim H. Vree, Merel A. Bouma, Michael Borst et al. (+3 more)
Spin waves are promising signal carriers for microwave control at the micrometer scale. However, realizing low-damping, tunable control of
spin-wave propagation remains a central challenge. Here we use
magnetic shielding by superconducting control elements to tune the local
spin-wave dispersion and realize temperature-controlled refraction of
spin waves in a thin-film
magnetic insulator. Using
magnetic imaging based on
spins in diamond, we characterize the refractive index and demonstrate both positive and negative refraction as well as wavefront shaping by the
superconductors. The observed refraction is explained by a geometrical analysis of the superconductivity-induced modification of the
hyperbolic spin-wave dispersion. Our results demonstrate that
superconductors enable tunable
spin-wave optical elements, opening new opportunities for microwave control in classical or
quantum information devices.
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All authors Pim H. Vree, Merel A. Bouma, Michael Borst, Tomas T. Osterholt, Rembert A. Duine, Toeno van der Sar
Mesoscale and Nanoscale Physics
Anderson Orthogonality as Measurement Backaction in Coupled Quantum Dots
Will Grant, Sarath Sankar, Elena Cornick et al. (+9 more)
Measurement perturbs a
quantum system by coupling it to external degrees of freedom, but detector backaction depends on the physical mechanism of measurement itself. In solid-state devices, detectors driven far from
equilibrium to enable faster measurements produce backaction that can often be understood as classical noise. However, a strong measurement can also induce backaction from
quantum many-body correlations in the detector that are intrinsic to the measurement, even without shot noise. Here, we probe this near-
equilibrium backaction through the effect of a
quantum-dot charge sensor on tunnelling between a second
quantum dot and its reservoirs. The measurement realizes the Anderson Orthogonality Catastrophe (AOC): electrons in the detector leads reorganize in response to an abrupt change in local scattering potential, suppressing resonant tunnelling while enabling inelastic processes that exchange energy with the detector. Changing the detector energy level tunes the AOC backaction from negligible to dominant in the tunnelling dynamics. More broadly, these results establish detector-induced many-body correlations as a controllable influence on
quantum dynamics.
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All authors Will Grant, Sarath Sankar, Elena Cornick, Vahid Movahed, Johann Drayne, Silvia Lüscher, Saeed Fallahi, Geoffrey C. Gardner, Michael J. Manfra, Eran Sela, Yigal Meir, Joshua Folk
Mesoscale and Nanoscale Physics
Effectiveness of Some 0 dB Cryogenic Microwave Attenuators as Thermal Heatsinks
J.T. Klomp, Haoyun Huang and G.A. Csathy
Coaxial cables are widely used in radiofrequency and microwave cryogenic setups for condensed matter and
quantum experiments. Since the inner conductor of coaxes is often in good thermal contact with the sample to be measured, it is desirable to know the phononic heat channeled by the inner conductor. Although cryogenic attenuators are widely used to thermalize the inner conductor of coaxes, to our knowledge, quantitative information is not available. We present data on the effectiveness of three commercially available 0 dB attenuators as thermal heatsinks. In particular, we measured the temperature of the inner pin of several 0 dB attenuators under a heat load. This information will aid in designing and carefully controlling the thermal environment of samples in high-frequency experiments mounted in dilution refrigerators and on nuclear demagnetization stages.
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Mesoscale and Nanoscale Physics
Theory of spin-wave transport in ferromagnet-superconductor heterostructures: Negative refraction, perfect imaging and temperature-controlled spin-wave optics
Tomas T. Osterholt, Thijs van der Meer, Pim H. Vree et al. (+4 more)
We investigate
spin-wave transport in ferromagnetic
insulator-
superconductor (FMI-SC)
heterostructures and develop a general theoretical framework for
spin-wave optics in these hybrid systems. We demonstrate that Meissner screening by the
superconductor gives rise to a range of unconventional wave phenomena, including negative phase- and group-velocity refraction, and reflection and refraction laws that differ fundamentally from their optical counterparts. Within this framework, we derive the
spin-wave Fresnel equations governing reflection and transmission at FMI-SC interfaces and show that the scattering properties exhibit a pronounced temperature dependence, enabling tunable
spin-wave mirrors and refractive elements. Most strikingly, we find that superconducting screening can produce nearly straight isofrequency contours, far flatter than the kinked, intrinsically curved contours attainable in conventional dipolar
spin-wave systems. We show that these straight contours enable functionalities such as perfect
spin-wave imaging, efficient waveguiding, and interferometric elements, such as phase shifters and beam splitters, with unconventional properties. Our results establish FMI-SC
heterostructures as a versatile platform for temperature-tunable
spin-wave optics and interferometric magnonic devices.
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All authors Tomas T. Osterholt, Thijs van der Meer, Pim H. Vree, Merel A. Bouma, Michael Borst, Toeno van der Sar, Rembert A. Duine
Mesoscale and Nanoscale Physics
Vector Edge Solitons and Domain Walls in a Nonlinear Mechanical Topological Insulator
David D. J. M. Snee and Yi-Ping Ma
We report nonlinear edge waves in a 2D mechanical topological
insulator. A bulk
lattice consists of pendulums with on-site cubic nonlinearity connected by linear springs realizing
quantum spin Hall effect. We show that the nonlinear interaction between two edge modes with equal group velocities (EGV) is described by a 1D two-component coupled nonlinear Schrödinger (CNLS) equation. On the interface separating two bulk
lattices with opposite
spin Chern numbers, we construct linear springs such that the dispersion relation exhibits EGV points with favorable CNLS coefficients. Thus, we realize nonlinear edge waves propagating along the interface, including bright-bright (BB) edge
solitons for focusing CNLS coefficients, and dark-dark edge
solitons, edge domain walls, and dark-bright edge
solitons for defocusing CNLS coefficients. In terms of the site amplitudes, these solutions resemble bright and dark breathers. These solutions should be topologically protected when both carrier frequencies lie within a band gap, which we explicitly show by passing BB edge
solitons through compact defects on the interface. We also show energy transfer in BB edge
soliton collisions with potential application to collision-based computing. Generally, vector edge
solitons exhibit a large parameter space for
soliton collisions, which endows mechanical devices with greater potential for information processing and other functionalities.
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Mesoscale and Nanoscale Physics
Multi-State Geometry of Density Matrices and Rectification Sum Rules
Barry Bradlyn
The geometry of
quantum states has emerged as a key ingredient in understanding the linear and nonlinear responses of
quantum materials. To date, however, the connection between geometry and nonlinear response is best understood for clean, noninteracting systems at zero temperature. In this work, we develop a theory of multi-state geometry for density
matrices and use it to derive sum rules for second-order rectification, making no assumptions about the strength of disorder or interactions. We first show that perturbation theory for thermal density
matrices gives rise to two dual information-theoretic connections and an almost complex structure. We introduce a complex,
quantum generalization of the Amari-Chentsov tensor of classical information theory, the cQAC tensor, which captures the multi-state geometry of the perturbed density
matrix. We derive a zero-temperature sum rule for the frequency-integrated DC rectification response of an
insulator as a difference between a ground state third cumulant and the complex distortion tensor, a multi-state
geometric quantity built from the cQAC tensor. This generalizes known single-particle sum rules for the shift and nonlinear Hall currents to many-body systems and general perturbations. Specializing to the shift current, we resolve the
geometric contribution for multiband
insulators into particle-like and hole-like terms. We verify the sum rule numerically in a generalized Kane-Mele model, finding that the
geometric contribution can dominate the integrated response. Finally, we show that although the splitting of the sum rule into cumulant and
geometric contributions does not survive at nonzero temperature, the measured sum rule for
insulators differs from its zero-temperature form by corrections exponentially small in the gap, allowing low-temperature rectification measurements to probe the multi-state geometry of
insulators.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Impact of Nonlinearities on Local Kinetic and Thermokinetic Uncertainty Relations in Bosonic Transport
Didrik Palmqvist, Luca Magazzù, Milena Grifoni et al. (+1 more)
The precision of transport observables can be bounded by the
entropy production and the activity of the transport process via kinetic and thermokinetic uncertainty relations. In linear bosonic systems, such uncertainty relations can provide tight bounds when the activity is replaced by a local activity of the measurement contact of interest—even in the strong-coupling regime. How much nonlinearities (or interactions) impact the validity and predictiveness of these local bounds and how much this impact depends on the concrete definition of activity are open questions that we address for two experimentally relevant model systems, a harmonic oscillator network and the intrinsically nonlinear
spin-
boson model. We thereby provide experimentally testable predictions on how nonlinearities impact or even break local kinetic and thermokinetic precision bounds.
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All authors Didrik Palmqvist, Luca Magazzù, Milena Grifoni, Janine Splettstoesser
Mesoscale and Nanoscale Physics
Anyon-Impurity Bound States in Quantum-Engineered Fractional Chern Insulators
Botao Wang, Amit Vashisht, Felix A. Palm et al. (+3 more)
Mobile impurities provide a powerful means of probing correlated and topological
quantum matter, through their dressing by the surrounding medium and the practical probes granting access to the resulting composite object. Motivated by the recent observation of anyon-impurity composites in the solid state, as well as recent realizations of Laughlin-type states in engineered
lattice systems, we investigate the formation of a bound state between a mobile impurity and a single pinned quasihole in the interacting Harper-Hofstadter model deep in the fractional Chern
insulator regime. Combining analytical arguments with large-scale numerical simulations, we characterize the structure, energetics, and stability of hybrid anyon-impurity bound states, and show that their binding energy provides direct access to the fractional charge of the quasihole under conditions that we identify. We further demonstrate that the composite object can be coherently transported by externally steering the quasihole pinning potential. Our results establish a realistic pathway for controlled anyon-impurity manipulation in
quantum-engineered platforms, enabling experimentally feasible protocols for braiding.
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All authors Botao Wang, Amit Vashisht, Felix A. Palm, Fabian Grusdt, Laurens Vanderstraeten, Nathan Goldman
Mesoscale and Nanoscale Physics
Geometric closure of classical nucleation theory for magnetic-field-controlled nanoparticle size across magnetic classes
Yazeed Tawalbeh and Mauro Fernandes Pereira
Controlling nanoparticle size during synthesis remains a central challenge in nanoscience, particularly in systems where external
magnetic fields are used as continuous control parameters. Existing descriptions of
magnetic-field-assisted nucleation are typically material-specific or rely on computationally intensive atomistic methods. Here, we reformulate classical nucleation theory as a geometrically closed thermodynamic framework by introducing a sphere-packing representation of atomic assembly. This construction establishes a direct link between discrete atomic structure and continuum free-energy contributions under applied
magnetic fields, yielding a field-driven
evolution equation for the critical
nucleus size. The resulting theory provides a unified description of nanoparticle nucleation across superparamagnetic, paramagnetic, and diamagnetic systems within a single formalism. It quantitatively reproduces previously unresolved experimental observations for magnetite and nickel nanoparticles, namely the systematic reduction of mean particle size and narrowing of size distributions with increasing
magnetic field. In the diamagnetic limit, the framework recovers our earlier analytical susceptibility-based description of silver nanoparticles, in which the field-dependent critical radius is governed by the induced-magnetization contribution to the nucleation free energy. Beyond modeling the reduction of mean particle size with increasing
magnetic field, the framework reveals that the narrowing of size distributions emerges naturally from the
curvature of the field-modified free-energy landscape. These results establish
magnetic-field-assisted nucleation as a geometrically constrained thermodynamic process, providing a computationally efficient route for controlling nanoparticle size across distinct
magnetic material classes.
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Mesoscale and Nanoscale Physics
Unconventional Scaling of Electric Hall Effect in Magnetic Weyl Semimetals
Chaoxi Cui, Yilin Han, Run-Wu Zhang et al. (+2 more)
Electric Hall Effect (EHE), a unique phenomenon in two-dimensional (2D)
magnetic systems, refers to the generation of Hall current by an out-of-plane electric field $\Ez$. Here, we demonstrate that for 2D
magnetic Weyl semimetals that host doubly degenerate nodal points, the EHE features multiple unconventional scaling laws. At zero temperature, the EHE exhibits a topological $E_F^{-1}$ Fermi-energy scaling. Remarkably, the prefactor of the scaling is determined by the global topological charge of the point without any dependence on the local parameters of the system, leading to a universal and significant enhancement of Hall response in any species of Weyl points as the Fermi energy approaches the Weyl point. This significant response enables a weak electric field to be directly converted into a measurable Hall signal. Surprisingly, this enhanced Hall response is not diminished by temperature, but evolves into an unconventional logarithmically corrected scaling at finite temperature $\sigma_{xy}\propto\Ez\ln(1/|\Ez|)$ for weak $\Ez$, still yielding a divergent electric-field susceptibility. Thus, our work not only unveils intriguing scaling laws resulting from the interaction between magnetism and
topology, but also suggests a novel scaling-enhanced and temperature-robust mechanism that may enable weak electric-field sensing through a practical and all-electric route.
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All authors Chaoxi Cui, Yilin Han, Run-Wu Zhang, Zhi-Ming Yu, Yugui Yao
Mesoscale and Nanoscale Physics
Beyond Electrons: A Theoretical Framework for Near-Field Radiative Thermal Computing and Neural-Network-Inspired Processing
Hexiang Zhang, Mauro Antezza and Yi Zheng
Near field radiative heat transfer provides a route for information processing in which thermal radiation, rather than charge transport, serves as the physical carrier of signals. Here, we propose and theoretically analyze a programmable near field radiative thermal computing framework in which radiative coupling, phase change nonlinearity, and thermal state
memory are mapped onto neural network inspired operations. The framework is constructed from near field radiative thermal diodes, transistors, and multi terminal logic units separated by nanoscale gaps. Radiative heat flux represents the propagated thermal information, while geometry and material dependent radiative coupling provides physically constrained weighting, and the temperature dependent optical response of phase-change materials enables nonlinear modulation and logic state control. Based on these primitives, we formulate a radiative thermal convolutional network for spatial information processing and a radiative thermal recurrent network for history dependent computation. The recurrent response is associated with radiative feedback, thermal relaxation, and phase change hysteresis, with VO2 providing history dependent short term
memory and GST offering a possible route toward non volatile phase storage. We further distinguish the physical radiative networks from a separate software based inverse identification study, in which recurrent machine-learning models are trained on simulated near field heat flux temperature characteristics to recover structural parameters. By establishing a bottom up connection between fluctuational electrodynamics, radiative thermal logic, programmable thermal states, and neural network inspired computation, this study provides a physically grounded basis for exploring non contact thermal information processing at the near field limit.
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Mesoscale and Nanoscale Physics
An Effective String Theory Toolbox for Quantum Hall Interfaces III: Open Worldsheets, Endpoint Conditions, and Branes
Ken K. W. Ma
A freely moving
quantum Hall (QH) interface may end on a physical edge or topological boundary, but fixed-edge theory cannot determine what endpoint data make such a termination consistent. Here we formulate an open-worldsheet junction framework in which the
embedding, material charge, anomaly flow, and topological boundary condition are organized together. The endpoint is specified by a
geometric support and variational boundary data, together with condensable topological sectors and any outgoing channels required to absorb or continue the worldsheet flux. This construction extends the charge–shape relation to an interval and shows why a lone chiral Majorana cannot terminate on a finite-dimensional endpoint degree of freedom. It gives an operational definition of a QH brane and a systematic basis for endpoint and network theories of dynamical QH interfaces.
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Mesoscale and Nanoscale Physics
An Effective String Theory Toolbox for Quantum Hall Interfaces II: Majorana Fermions on Fluctuating Moore-Read Worldsheets
Ken K. W. Ma
A Moore–Read interface carries a chiral Majorana mode on a boundary whose geometry may itself fluctuate. Fixed-edge theory does not determine how this neutral mode should be transported when the interface bends and moves, or how its dynamics couples to the fluctuating shape. Here we construct a spatially reparametrization-invariant Majorana theory on the nonrelativistic worldsheet of a freely moving interface. The changing line element fixes a universal half-density transport law, while additional
curvature- and velocity-dependent couplings remain controlled by microscopic interface physics. The resulting framework identifies the Majorana stress tensor as the mediator between neutral and
geometric dynamics and provides the neutral sector needed for effective theories of dynamical non-Abelian
quantum Hall interfaces.
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Mesoscale and Nanoscale Physics
An Effective String Theory Toolbox for Quantum Hall Interfaces I: Worldsheet Kinematics and Constraint Structure
Ken K. W. Ma
A freely moving
quantum Hall interface is fundamentally different from an ordinary edge fixed by an external confining potential. Since a normal displacement changes the areas occupied by the adjacent incompressible phases, the interface geometry and charge dynamics cannot be treated as independent degrees of freedom. We formulate this problem for interfaces between Abelian
quantum Hall phases using a spatially reparametrization-invariant worldsheet description, in which tangential motion is a relabeling of the interface while normal motion is physical. Starting from the two-sided Chern–Simons response, we derive the relation between normal charge transport and interface motion. We then introduce a relative-area construction, defined with respect to a material reference curve, that converts this velocity relation into an equal-time constraint linking the charged boundary sector to the interface shape. Combined with the folded $K$-
matrix current
algebra, this identifies the universal Hall kinematics of the moving interface while leaving its
geometric energy and neutral dynamics dependent on microscopic interface physics. The resulting framework provides a systematic basis for effective theories of dynamical
quantum Hall interfaces.
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Mesoscale and Nanoscale Physics
One-dimensional Dirac modes in the core of a pentagonal topological crystalline insulator nanowire
Saeed Samadi, Rafał Rechciński, Marta A. Chabowska et al. (+1 more)
We investigate the electronic band
topology of recently fabricated pentagonal IV-VI
semiconductor nanowires, which contain five radial $\{111\}$ twin planes meeting at the nanowire axis. Tight-binding calculations show that, when the bulk band structure is inverted and the twin planes in the nanowire are cationic, the spectrum contains two spatially separated helical Dirac crossings near $\overline{\Gamma}$: one localized at the core and the other at the outer surface. When the twin planes are anionic, the corresponding spectra remain gapped. The crossings originate from the hybridization of five helical channels associated with the twin-plane edges, whose odd number leaves one Kramers pair near the nanowire axis and the other at the outer boundary. Realistic multiorbital calculations for $\mathrm{Pb}_{0.4}\mathrm{Sn}_{0.6}\mathrm{Te}$ predict well-developed core and surface modes at nanowire thicknesses of approximately 50~nm and above. These results establish pentagonal SnTe-class nanowires as an experimentally accessible realization of spatially separated helical channels bound to the axial defect and the outer boundary.
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All authors Saeed Samadi, Rafał Rechciński, Marta A. Chabowska, Ryszard Buczko
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.mtrl-sci
Tuning the Optoelectronics of Mixed-Semiconductors through the interplay of Quantum confinement and Stoichiometry Engineering
Kanha Ram Khator, Anupam Manna, Amlandeep Nayak et al. (+3 more)
All-inorganic cesium lead bromide (CsPbBr3) nanocrystals (NCs) have established themselves as an emerging
semiconductor for next-generation optoelectronic technologies due to their unique combination of properties, such as near unity photoluminescence
quantum yields, narrow color pure emission, and exceptional defect tolerance. Although size-dependent optical signatures of these NCs are well reported, the complexity of mixed ionic-electronic transport remains largely unexplored. In this study, we provide a comprehensive analysis of size-dependent charge transport by decoupling ionic and electronic transport dynamics through carefully designed transient current and space charge limited current measurements. By employing NCs of different sizes ranging from 5.6 nm to 11.3 nm in thin films, we provide a comprehensive understanding of
quantum confinement effects and related synthetic chemistry. Contrary to popular beliefs of
quantum confinement and band gap broadening, our results demonstrate that the smallest NCs exhibit the most efficient transport characteristics, evidenced by the lowest activation energy (hole activation energy = 78 meV) for hole transport and the highest barrier for vacancy-mediated ion migration (ion activation energy = 370 meV). This work paves a way forward for perovskite-based efficient
quantum devices, by demonstrating that moving into a strong
quantum confinement regime, a superior charge transport can be facilitated, when supported by carefully tailored stoichiometry.
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All authors Kanha Ram Khator, Anupam Manna, Amlandeep Nayak, Pravat Nayek, Prasenjit Mal, Satyaprasad P Senanayak
Mesoscale and Nanoscale Physics
Impact of spin-orbit coupling on electron correlation corrections to the density of states in anisotropic conductors
Bahruz Suleymanli and B. Tanatar
We study Altshuler-Aronov-type interaction corrections to the single-particle density of states (DOS) in a strongly anisotropic 2D conductor with an open Fermi surface (FS) and weak disorder, in the presence of coexisting Rashba and Dresselhaus
spin-orbit couplings (SOCs) constrained to the longitudinal direction. The low-energy band consists of two warped sheets weakly tunnel-coupled transversely; SOC splits the sheets into helicity branches with a fixed
spin axis. Working in a Matsubara space, we compute the exchange contribution in the
diffusion channel with dynamically screened Coulomb interaction and an impurity ladder. The resulting DOS anomaly exhibits a dimensional crossover governed by the transverse coupling scale $\varepsilon_c$. Close to the Fermi level ($|\varepsilon-\varepsilon_F|<\varepsilon_c$), the system behaves two-dimensionally, featuring a logarithmic DOS dip whose magnitude is enhanced by intrinsic SOCs. Further from the Fermi level ($|\varepsilon-\varepsilon_F|\!>\!\varepsilon_c$), the system behaves quasi-one-dimensionally, featuring a sharper square-root singularity whose amplitude is remarkably enhanced by the SOCs. Notably, we identify a critical SOC strength at which these
spin-orbit effects exactly cancel the electron-correlation correction, perfectly restoring the unperturbed density of states. Furthermore, increasing the SOC beyond this critical point inverts the sign of the anomaly entirely, yielding a positive DOS correction. This sign reversal fundamentally alters the energy dependence, such that at energies beyond $\varepsilon_F + \varepsilon_c$, the positive correction decays to smaller values as energy increases, opposite to the standard negative correction. This contrasting trend provides a distinct spectroscopic signature of SOC-modulated correlation effects.
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Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.mtrl-sci
Interface Engineering of Helium Confinement in Argon-Preplated MCM-41 Nanopores
Rahul Soni, Nathan S. Nichols, Sutirtha Paul et al. (+3 more)
Atomic-scale modification of mesopore interfaces provides a route to tune the confinement experienced by adsorbed fluids, but how a specific interface preparation translates into the resulting microscopic confinement potential remains unclear. Here, we show that preplating MCM-41 with an argon monolayer modifies the effective pore interface by occupying strongly attractive regions of the heterogeneous silica surface and screening its atomic-scale corrugation. Grand-canonical Monte Carlo simulations of argon adsorption, low-temperature molecular dynamics, and helium test-particle insertion are combined with adsorption isotherms and
neutron-scattering measurements to characterize the preplated pore at the atomic scale. Helium test-particle insertion calculations show that the modified interface shifts the helium adsorption minimum to an annular region inside the pore and produces a confinement landscape dominated by a smooth radial component. The resulting radial confinement potential can be described by a continuum cylindrical model, providing microscopic support for the effective potential used in earlier
quantum Monte Carlo studies. Residual corrugation persists over multiple spatial scales and is accurately captured by a Gaussian process surrogate. These results demonstrate how atomic preplating can tailor nanopore confinement and provide an experimentally constrained microscopic potential for predictive studies of confined
quantum fluids.
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All authors Rahul Soni, Nathan S. Nichols, Sutirtha Paul, Garfield Warren, Paul Sokol, Adrian Del Maestro
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.str-el
Strongly Enhanced Charge-Density Waves and Correlated Insulating State in Atomically Thin 1$T$-TaS$_2$
Gan Liu, Yulu Liu, Qiling Luo et al. (+7 more)
We investigate thickness-dependent charge-density-wave (CDW) transitions in 1$T$-TaS$_2$ using temperature-dependent Raman spectroscopy and electrical transport. Raman measurements show that the incommensurate, nearly commensurate, and commensurate CDW phases persist down to the monolayer limit. As the thickness is reduced, the transition temperatures increase, accompanied by an orders-of-magnitude rise in sheet resistance and a sharp reduction in the carrier localization length. The first-order hysteretic CCDW-NCCDW transition is uniquely absent in the monolayer. Calculations suggest that the enhanced CDW in thin layers originates from strengthened Coulomb interactions due to reduced out-of-plane screening, particularly in the nonlocal component. These findings highlight the cooperative roles of electron correlation, electron-
phonon interaction, and interlayer coupling in shaping the ground state and transition dynamics of atomically thin 1$T$-TaS$_2$, opening pathways for engineering correlated phases in two-dimensional CDW systems.
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All authors Gan Liu, Yulu Liu, Qiling Luo, Zhentao Huang, Kenji Watanabe, Takashi Taniguchi, Meiyu Wang, Jinsheng Wen, Yi Lu, Xiaoxiang Xi
Mesoscale and Nanoscale Physics · Cross-listed from cond-mat.mtrl-sci
Intra-unit-cell resolved intertwining of multi-$Q$ charge and spin textures in an itinerant skyrmion magnet
Christopher J. Butler, Katsuki Nihongi, Haruto Yoshimochi et al. (+4 more)
The mechanisms stabilizing non-collinear magnetism in centrosymmetric
crystals remain unclear, but likely involve
spin-
spin interactions mediated by itinerant electrons, such as the RKKY interaction. Finite-$Q$
magnetic order may then be accompanied by electronic modulations that are observable using a scanning tunneling microscope. In five successive
magnetic phases of GdRu$_{2}$Ge$_{2}$, including two nano-scale skyrmion
crystal phases, we show that multi-$Q$ magnetism among Gd 4$f$
spins entails a corresponding multi-$Q$ texture among the Ru 4$d$ orbitals that contribute itinerant electron bands. With atomically-resolved images of each electronic texture's motif, and a simple numerical modeling scheme drawing on the underlying
spin structures, we infer their key relationship: The
alignment between nearest-neighbor Gd
spins tightly correlates with the local density-of-states of the Ru 4$d$ orbitals on the two bond-centered sublattices of the Gd square net. These analyses offer a microscopic view of the atomic-scale intertwining of charge and
spin degrees-of-freedom in non-collinear itinerant magnets.
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All authors Christopher J. Butler, Katsuki Nihongi, Haruto Yoshimochi, Nguyen Duy Khanh, Rina Takagi, Tetsuo Hanaguri, Shinichiro Seki