Materials Science
Epitaxial SiGeSn alloys for CMOS-compatible thermoelectric devices
Patrizio Graziosi, Damiano Marian, Andrea Tomadin et al. (+7 more)
The integration of thermoelectric devices into mainstream microelectronic technological platform could be a major breakthrough in various fields within the so-called Green-IT realm. In this article, the thermoelectric properties of heteroepitaxial SiGeSn
alloys, a novel CMOS compatible material system, are evaluated to assess their possible application in thermoelectric devices. To this purpose, starting from the experimentally low
lattice thermal conductivity of SiGeSn/Ge/Si layers of about $\sim$1-2 W/m$\cdot$K assessed by means of 3-$\omega$ measurements, the figure of merits are calculated through the use of Boltzmann transport equation, taking into account the relevant inter-valley scattering processes, peculiar of this multi-valley material system. Values for the figure of merit $ZT$ exceeding $1$ have been obtained for both p- and n- type material at operating temperatures within the 300—400 K range, i.e. at a typical On-Chip temperatures. In this interval, the predicted power factor also features very competitive values of the order of 20 $\rm{\mu W/cm\cdot K^2}$. Our finding indicates that this new class of Si-based materials has extremely good prospects for real-world applications, and can further stimulate scientific investigation in this ambit.
Read the full abstract ▾
All authors Patrizio Graziosi, Damiano Marian, Andrea Tomadin, Stefano Roddaro, Omar Concepción, Johnny Tiscareño-Ramírez, Agnieszka Anna Corley-Wiciak, Dan Buca, Giovanni Capellini, Michele Virgilio
Materials Science
Toward two dimensional MoS2 electrets
Eugenio Lunedei, Andrea Liscio, Francesco Borgatti et al. (+8 more)
Here, we show that controlled sulfur vacancy engineering converts monolayer MoS2 into an electret, imparting the ability to store quasi-permanent electrostatic charge within a single atomic layer. Sulfur vacancies are generated with submicrometer spatial control by stamp-assisted electrode-free electrochemical nanolithography, yielding programmable defect densities from 10 10 to 10 13 1 cm-2. The resulting vacancy domains act as deep electron traps and produce surface charge densities up to 1 uCcm-2, with charge retention in the order of hundreds days under ambient conditions. Kelvin probe and electric force microscopies directly reveal stable electrostatic patterns that replicate the lithographic motif. The same vacancy landscape simultaneously defines
exciton-quenching regions, generating co-localized optical and electrostatic contrast and reducing the apparent
exciton lifetime from 15 ns to 180 ps through enhanced nonradiative recombination. The persistence of the optical response over one year identifies sulfur vacancies, rather than transient charge states, as the origin of the patterned functionality. These results establish defect-engineered MoS2 as the first two-dimensional electret and demonstrate that atomic vacancies can be exploited as functional elements for encoding electrostatic and excitonic behavior in a single atomic layer.
Read the full abstract ▾
All authors Eugenio Lunedei, Andrea Liscio, Francesco Borgatti, Edoardo Chini, Pasquale DAngelo, Fiorenza Esposito, Niccolo Borghi, Matteo Mannini, Denis Gentili, Luca Seravalli, Massimiliano Cavallini
Materials Science
Strain Tuning of Orbital-Driven Giant Magnetoresistance in van der Waals ferrimagnet Mn$_3$Si$_2$Te$_6$
Abdul Ahad, Miuko Tanaka, Shunta Aoki et al. (+7 more)
Strain engineering of magnetotransport offers a powerful strategy for uncovering emergent electronic and domain phenomena in
quantum magnetic materials, while providing a promising pathway toward next-generation mechanically programmable spintronic technologies. Van der Waals magnets are particularly attractive in this context because their high crystallinity and mechanical flexibility allow exceptionally large, precisely controllable strain, enabling access to strain-induced functionalities unattainable in conventional solids. Here, we report systematic strain control of the van der Waals magnet Mn$_3$Si$_2$Te$_6$, which exhibits an unconventional colossal magnetoresistance whose microscopic origin remains under debate. We demonstrate in situ large-strain modulation of the electrical resistance in bulk
crystals and show that the effect can be consistently explained by strain-tunable chiral orbital-current domains. Furthermore, measurements on exfoliated flake devices containing a single chiral domain reveal direct strain control of the electronic structure affected by orbital
magnetic moment, establishing a unified microscopic mechanism for the unconventional colossal magnetoresistance. These results identify strain as an exceptionally effective control parameter for tailoring electronic and
magnetic states in van der Waals magnets and provide a conceptual framework for realizing
spin-straintronic functionalities based on orbital degrees of freedom.
Read the full abstract ▾
All authors Abdul Ahad, Miuko Tanaka, Shunta Aoki, Darius-Alexandru Deaconu, Varun Shah, Tenta Kitamura, Hao Ou, Mohammad Saeed Bahramy, Jiang Pu, Toshiya Ideue
Materials Science · Cross-listed from cond-mat.str-el
Emergence and Detection of Surface altermagnetism in KV$_2$Se$_2$O
Rodrigo Jaeschke-Ubiergo, Xanthe H. Verbeek, Colin Lange et al. (+4 more)
We demonstrate the recent concept of emergent surface altermagnetism through its unique signatures in \KVSO. We show that for bulk antiferromagnetically ordered \KVSO, the (001) surface exhibits $d$-wave altermagnetism. Our results fully explain the recent seemingly contradicgting experimental evidence, independently showing both an antiferromagnetically ordered bulk from
neutron diffraction, and $d$-wave
spin splitting from photoemission spectroscopy. To fully verify this conecept, we predict, as a key experimental signature, a large nonlinear Edelstein response, which is localized at the surface, and follows the $d$-wave altermagnetic
symmetry. These results are not only relevant for the metallic and room-temperature magnet \KVSO, but also for several other Lieb
lattice systems. Our work expands the pool of techniques that can be used to detect altermagnetism emerging at the surfaces of antiferromagnets.
Read the full abstract ▾
All authors Rodrigo Jaeschke-Ubiergo, Xanthe H. Verbeek, Colin Lange, Sergio Rodriguez, Atasi Chakraborty, Alexander Mook, Jairo Sinov
Materials Science · Cross-listed from cond-mat.str-el
Manipulation of localized excitons in CrPS$_4$ by temperature and magnetic field
Dipankar Jana, Swagata Acharya, Amit Pawbake et al. (+9 more)
Layered van der Waals
magnetic semiconductors provide a versatile platform for exploring excitonic phenomena intertwined with
spin and
lattice degrees of freedom, enabling
excitons to act as sensitive probes of
magnetic order. CrPS$_4$ is a layered antiferromagnetic
semiconductor that hosts rich excitonic features whose microscopic origin and connection to
magnetic ordering remain incompletely understood. Here, we investigate the electronic and excitonic properties of bulk CrPS$_4$ using a combination of many-body perturbation theory, dynamical mean-field theory, and photoluminescence-based experiments. Our calculations establish CrPS$_4$ as a direct-gap
semiconductor with a bandgap of 2.48~eV in the antiferromagnetic phase. Several sub-bandgap excitonic transitions are predicted by theory, comprising multiple
spin-allowed
excitons and an additional
spin-flip excitation, predominantly localized on the Cr$^{3+}$ ions. Temperature- and
magnetic-field-dependent optical measurements reveal thermally driven
exciton redistribution among localized states and identify characteristic energy shifts that provide clear optical signatures of
magnetic phase transitions in CrPS$_4$. These results provide new insights into the excitonic transitions of antiferromagnets and suggest potential routes for all-optical sensing and light-driven control of their
magnetic order.
Read the full abstract ▾
All authors Dipankar Jana, Swagata Acharya, Amit Pawbake, Dmitrii Litvinov, Aljoscha Soll, Zdenek Sofer, Clement Faugeras, Dimitar Pashov, Mark van Schilfgaarde, Kostya S. Novoselov, Marek Potemski, Maciej Koperski
Materials Science
The New High-entropy Compound RhMnFeCoGe4 with Cubic Non-centrosymmetric B20 Structure
V. A. Sidorov, V. N. Krasnorussky, A. V. Bokov et al. (+8 more)
A novel high-
entropy compound, RhMnFeCoGe$_4$, with a cubic non-centrosymmetric B20 struc- ture, has been synthesized under conditions of high pressure and temperature. The electrical transport and
magnetic properties of the obtained compound at both ambient and elevated pres- sures have been investigated. In addition, nuclear
magnetic resonance (NMR) spectra were obtained at 4.2 K and ab initio calculations were performed. The new material exhibits ferromag- netic behavior with a critical temperature of $T_C$ = 146 K and a spontaneous moment of 2.5 $\mu_B$ per formula unit. The magnetization data obtained at the critical region yielded the critical temperature and exponents, which were found to be $T_C$ = 146(1) K, $\beta$ = 0.337(1), $\gamma$ = 1.121(1), and $\delta$ = 4.326(1). The
magnetic moments of Mn and Co were determined from NMR spectra to be 2.2 $\mu_B$ and 0.5 $\mu_B$, respectively. Ab initio calculations yielded reasonable values for the
lattice parameter and the
magnetic moments of all constituents. The density of states and band structure are determined for both paramagnetic and ferromagnetic states.
Lattice compression results in the increase in the $T_C$.
Read the full abstract ▾
All authors V. A. Sidorov, V. N. Krasnorussky, A. V. Bokov, Z. N. Volkova, A. P. Gerashchenko, N. M. Chtchelkatchev, M. V. Magnitskaya, D. A. Salamatin, A. V. Semeno, V. V. Brazhkin, A. V. Tsvyashchenko
Materials Science · Cross-listed from cond-mat.mes-hall
Vector-field control and emergent basal-plane anisotropy of magnetic textures in noncentrosymmetric (Fe$_{0.63}$Ni$_{0.3}$Pd$_{0.07}$)$_3$P
Victor Ukleev, Oleg I. Utesov, Lorenzo Ubilla et al. (+17 more)
(Fe$_{0.63}$Ni$_{0.3}$Pd$_{0.07}$)$_3$P is a room-temperature magnet with $S_4$
symmetry that hosts a rich variety of topological
spin textures. Here, we report a combined resonant small-angle x-ray scattering and ptychography study of (Fe$_{0.63}$Ni$_{0.3}$Pd$_{0.07}$)$_3$P in vector
magnetic fields over a broad temperature range. We demonstrate deterministic vector-field control of
magnetic stripe domains, where in-plane fields continuously rotate their orientation via a transition from a chiral stripe to an achiral fan configuration. Furthermore, at 50 K and below, the stripe orientation becomes metastably pinned and retains its field-trained direction. While the magnitude of the wavevector is nearly isotropic within the basal plane at room temperature, a pronounced temperature
evolution of anisotropic interactions emerges upon cooling. In particular, non-trivial anisotropy axes develop at 20-50 K reflecting the combined effects of magnetocrystalline anisotropy, anisotropic exchange, and Dzyaloshinskii-Moriya interaction (DMI), whose effective orientation is found to rotate with temperature. These results establish (Fe$_{0.63}$Ni$_{0.3}$Pd$_{0.07}$)$_3$P as a model system for vector-field control of chiral
spin textures and reveal a previously unrecognized temperature-driven
evolution of the effective DMI landscape in a noncentrosymmetric magnet.
Read the full abstract ▾
All authors Victor Ukleev, Oleg I. Utesov, Lorenzo Ubilla, Chen Luo, Radu-Marius Abrudan, Peter Wild, Holger Kropf, Moritz Winter, Sebastian Schneider, Alexander Tahn, Bernd Rellinghaus, Tim A. Butcher, Simone Finizio, Sebastian Wintz, Markus Weigand, Max T. Birch, Yoshinori Tokura, Yasujiro Taguchi, Kosuke Karube, Florin Radu
Materials Science
Spin-Chirality-Driven Bulk Photovoltaic Effect in van der Waals Magnet CrSBr
Dezhao Wu, Yong Xu, Meng Ye et al. (+1 more)
The bulk photovoltaic effect (BPVE) can be greatly enriched in
magnetic materials. Here, we establish vector
spin chirality as a tunable knob for generating an unconventional time-reversal-even
magnetic BPVE, comprising the chiral shift current (CSC) and chiral injection current (CIC). Using bilayer antiferromagnetic (AFM) CrSBr as a prototype, we theoretically demonstrate the emergence of CSC and CIC. Compared with conventional photovoltaic currents arising from noncentrosymmetric
crystal structures or collinear
magnetic orderings, CSC and CIC not only possess comparable magnitudes but also exhibit exceptional tunability. Specifically, they can be switched on and off by
magnetic-field-induced
spin canting, reversed in direction upon canting-direction reversal, and continuously modulated in intensity via canting-angle variation. Furthermore, we reveal an unusual optical transition channel governing both currents in CrSBr. Our work establishes an unconventional
magnetic BPVE with remarkable controllability, paving the way for applications in optoelectronics and
magnetic sensing in noncollinear magnets.
Read the full abstract ▾
All authors Dezhao Wu, Yong Xu, Meng Ye, Wenhui Duan
Materials Science
Anisotropic Phonon Heat Flow and Thermoelectric Response in Tetragonal GeS$_2$ and GeSe$_2$
Neeraj Kulhari, Krishna Swaroop Sharma and K. C. Bhamu
The electronic structure,
lattice dynamics, bonding, elastic response, and anisotropic thermoelectric transport properties of tetragonal GeS$_2$ and GeSe$_2$ were investigated using density functional theory, density functional perturbation theory, Wannier interpolation, and scattering-aware Boltzmann transport. The relaxed structures are mechanically and dynamically stable within the calculated harmonic description. The HSE03/Wannier band gaps are 2.48 eV for GeS$_2$ and 1.23 eV for GeSe$_2$, while substitution of S by Se lowers the upper
phonon frequency from approximately 13.6 to 10.3 THz. The
phonon Boltzmann transport calculations reveal pronounced
lattice-transport anisotropy. Within the relaxation-time approximation, the 300 K in-plane and cross-plane
lattice thermal conductivities are 26.86 and 1.19 W m$^{-1}$ K$^{-1}$ for GeS$_2$, and 18.74 and 1.52 W m$^{-1}$ K$^{-1}$ for GeSe$_2$, respectively. At 800 K, these values decrease to 10.22 and 0.46 W m$^{-1}$ K$^{-1}$ for GeS$_2$, and 7.25 and 0.58 W m$^{-1}$ K$^{-1}$ for GeSe$_2$. Frequency-resolved analysis shows that low-frequency
phonons carry most of the heat, whereas the small cross-plane values reflect restricted out-of-plane
phonon transport. Combining the ShengBTE RTA
lattice tensors with AMSET electronic coefficients gives $zT=0.257$ for n-type cross-plane GeS$_2$ at 800 K and $10^{19}$ cm$^{-3}$. The corresponding PBE-AMSET estimate for GeSe$_2$ is $zT=0.066$ for p-type cross-plane transport at 800 K and $3\times10^{20}$ cm$^{-3}$. LOBSTER analysis identifies mixed covalent–ionic Ge–X bonding, with Ge–S bonds having a larger stabilizing ICOHP magnitude than Ge–Se bonds ($-5.27$ versus $-4.74$ eV per bond). These results identify tetragonal GeX$_2$ compounds as strongly anisotropic thermoelectrics with moderate calculated $zT$ values whose cross-plane response benefits from suppressed
lattice heat transport.
Read the full abstract ▾
Materials Science
Magnetic and crystal electric field excitations in a spin-orbit coupled frustrated hyperkagome magnet Nd$_3$Li$_3$W$_2$O$_{12}$
R. Kolay, S. Guchhait, Indrajeet S. Rathore et al. (+4 more)
Rare-earth based garnets provide a viable platform for studying the frustrated driven
magnetic properties of the hyperkagome
lattices. Herein, we report a comprehensive study of the
magnetic properties and
crystal electric field (CEF) scheme of a new Nd$^{3+}$ based hyperkagome antiferromagnet, Nd$_3$Li$_3$W$_2$O$_{12}$ belonging to the garnet family via magnetization, heat capacity, and inelastic
neutron scattering (INS) measurements. Magnetization measurement reveals a dominant antiferromagnetic interaction with a low temperature Curie-Weiss temperature $\theta_{\rm CW}^{\rm LT} \simeq -0.2$ K. Two broad maxima are observed in the
magnetic heat capacity data under
magnetic fields, implying multilevel Schottky anomalies due to the effect of CEF and display a two-step
magnetic entropy release. No
magnetic long-range order is observed down to 0.1 K. The CEF excitations of the Nd$^{3+}$ ($J=9/2$) ion with $D_2$ point group
symmetry, probed via INS experiments, show non-dispersive excitations characterizing the transitions among the CEF energy levels. The simultaneous fit of the INS spectra at different temperatures enabled the mapping of the CEF
Hamiltonian and the energy
eigenvalues of the Kramers' doublets. The simulation using the obtained CEF parameters reproduces the experimental
magnetic susceptibility,
magnetic isotherms, and
magnetic heat capacity data. The thermodynamic properties and INS-derived
crystal-field scheme confirm a Kramers' doublet ground state with an effective
spin $J_{\rm eff} = 1/2$ at low temperatures.
Read the full abstract ▾
All authors R. Kolay, S. Guchhait, Indrajeet S. Rathore, S. Nandi, M. D. Le, N. B. Christensen, R. Nath
Materials Science
Alloy engineering of excitonic properties in TMD monolayers
Eirini Katsipoulaki, Adlen Smiri, Panagiotis Spiliotakis et al. (+12 more)
We investigate monolayer MoS$_{2x}$Se$_{2(1-x)}$
alloys across the full composition range using optical spectroscopy. We demonstrate continuous tuning of the optical gap over $\sim$0.35 eV, accompanied by a systematic reduction of the B–A
exciton splitting, in agreement with density functional theory calculations. Temperature-dependent measurements reveal a progressive increase of the average
phonon energy from Se-rich to S-rich
alloys that follows a simple reduced-mass scaling model. Polarization-resolved spectroscopy further shows a monotonic increase of the circular polarization from nearly zero in MoSe$_2$ to $\sim$15% in MoS$_2$ at 78 K. The observed
evolution of the polarization is attributed to
alloy-induced modifications of the electronic structure that modify bright–dark
exciton mixing and the associated valley depolarization. These findings establish
alloy engineering as an effective strategy for controlling excitonic properties in TMD monolayers.
Read the full abstract ▾
All authors Eirini Katsipoulaki, Adlen Smiri, Panagiotis Spiliotakis, Konstantinos Mourzidis, Danae Katrisioti, Takashi Taniguchi, Kenji Watanabe, Georgios Kopidakis, Zdenek Sofer, Gang Wang, Emmanuel Stratakis, George Kioseoglou, Iann C. Gerber, Xavier Marie, Ioannis Paradisanos
Materials Science
Picometre-scale real-time drift correction in TEM and STEM by dynamic control of the specimen stage for atomic-resolution imaging
Christophe Gatel, Julien Dupuy, Teresa Hungria et al. (+1 more)
In this work, we show how the specimen drift can be actively compensated by controlling the stage with precision down to the picometre scale. We do this by dynamic control, a generic real-time feedback framework designed to actively stabilize electron microscopy experiments by continuously monitoring an experimental variable from the detector data stream and compensating its
evolution during acquisition. The framework, applicable to a broad range of controllable experimental instabilities, includes automated calibration procedures, operates in parallel with image acquisition and is implemented as a software plugin without requiring any hardware modification of the microscope. Results for live drift correction are shown for a selection of TEM and STEM instruments using conventional mechanical stages as well as piezoelectric stages. Experimental results are presented for medium resolution TEM, high-resolution TEM, HR-STEM and in situ observations. With piezoelectric stages, specimen stabilization down to the picometre scale was achieved allowing drift-corrected atomic-resolution imaging. Specimen stage-based stabilization significantly improves long-exposure imaging and in situ experiments by increasing the effective exposure time, preserving the field of view, maintaining identical optical conditions and eliminating the need for numerical
alignment of large
datasets. Beyond the specific application presented here, dynamic control provides a versatile framework for real-time regulation of electron microscopy experiments and opens new perspectives for quantitative imaging, automated in situ studies and
multimodal acquisitions.
Read the full abstract ▾
All authors Christophe Gatel, Julien Dupuy, Teresa Hungria, Martin J. Hytch
Materials Science
Bias Tunable Transport Modulation and Gas Selectivity in Layered BiOI: A DFT NEGF Study
Jemal Yimer Damte, Jiří Houška, Pavel Baroch et al. (+1 more)
Understanding the interplay between adsorption energetics and charge-transport modulation is essential for the rational design of low-power and bias-tunable gas sensors. Here, we present a comprehensive first-principles study of gas selectivity in layered bismuth oxyiodide (BiOI) by integrating density functional theory with nonequilibrium Green's function transport calculations. The adsorption and bias-dependent transport responses toward NO2, NH3, CO2, and representative volatile organic compounds are systematically examined. While NH3 and NO2 exhibit strong chemisorption and localized electronic perturbations, CO2 interacts through weak physisorption, demonstrating that adsorption strength alone does not determine sensing performance. Instead, the
evolution of transmission channels near the Fermi level governs the sensing response. Bias-dependent calculations reveal an electrically tunable sensitivity hierarchy, in which weakly adsorbed CO2 preserves conductive pathways and exhibits pronounced low-bias sensitivity despite minimal charge transfer. Recovery-time analysis further highlights the trade-off between transport modulation and reversibility for strongly adsorbed species. These results establish a transport-centered selectivity framework for layered BiOI and provide mechanistic insight into electric-field-controlled gas sensing under ambient conditions.
Read the full abstract ▾
All authors Jemal Yimer Damte, Jiří Houška, Pavel Baroch, Xue Yong
Materials Science
AccelNet: Exact backward-compatible acceleration of polynomial angular descriptors through Cartesian moment factorization
Yuki Nagai
We present AccelNet, an exact, backward-compatible method for accelerating existing trained aenet and n2p2 neural-network potentials without retraining. For angular terms with separable one-neighbor weights and a finite
polynomial dependence on $\cos \theta$, the method exploits their hidden finite-rank structure to replace explicit neighbor-pair loops by one-neighbor Cartesian moments. AccelNet reads models trained with either package and reproduces their descriptors, energies, and analytic forces to floating-point roundoff. We verified this equivalence for H$_2$O and TiO$_2$ models and tested the resulting potentials in LAMMPS molecular-dynamics simulations. The implementation, model-conversion tools, and LAMMPS interfaces are released as open-source software. AccelNet also enables GPU-accelerated molecular dynamics with existing aenet and n2p2 potentials. Moment evaluation achieves speedups of up to 10.9 on a CPU and 15.8 on a GPU relative to direct evaluation within AccelNet. The implementation, model-conversion tools, and LAMMPS interfaces are released as open-source software.
Read the full abstract ▾
Materials Science · Cross-listed from cond-mat.str-el
Fluctuations of topological charges in two-dimensional classical Heisenberg model through high-temperature and low-temperature expansions
Shan-Chang Tang
It is well known that KT transition in 2d XY model is driven by the binding and unbinding of topological defects, which can be characterized by the fluctuation of topological charges inside a region. We extend the idea into the 2d Heisenberg model and calculate the fluctuation through high-temperature and low-temperature expansion respectively. It is found that the fluctuation of topological charges is proportional to the area of the region at high temperatures while obeys the perimeter law at low temperatures.
Read the full abstract ▾
Materials Science
Apparent Dresselhaus coefficient in (001) GaAs quantum wells: Correlation-time renormalization in D'yakonov-Perel' spin relaxation
Yuzo Ohno, Jun Ishihara and Satoshi Iba
We study the Dresselhaus coefficient inferred from D'yakonov-Perel'
spin relaxation in bulk GaAs and (001) GaAs
quantum wells using nonballistic Monte Carlo simulations. In bulk GaAs, inelastic LO-
phonon simulations reproduce the
spin relaxation with a cubic Dresselhaus coefficient \gamma_{3D}\simeq12.4 eVÅ^3 and a cubic-field correlation time \tau_3^{3D}\simeq150 fs. In a projected two-dimensional
quantum-well model, however, k_z^2 is replaced by the static expectation value \langle k_z^2 \rangle, converting the dominant Dresselhaus field into a term linear in the in-plane wave vector. We show that this projection changes the D'yakonov-Perel' correlation kernel from K_3^{2D} to a first- and third-order hybridized kernel K_{1+3}^{2D}, for which the correlation time \tau_{1+3}^{2D} approaches 235 fs in the strict two-dimensional limit, in contrast to the third-order correlation time \tau_3^{2D} of 130 fs. Consequently, the coefficient entering the projected two-dimensional model is not the intrinsic cubic coefficient itself but an apparent coefficient, \gamma_{2D}^{app}=\gamma_{3D} \sqrt{\tau_3^{2D}/\tau_{1+3}^{2D}}. Since \tau_{1+3}^{2D}\simeq1.8\tau_3^{2D} under LO-
phonon-dominated scattering, \gamma_{2D}^{app}\simeq9.2 eVÅ^3, consistent with
spin relaxation in (001) GaAs
quantum wells. This correlation-time renormalization clarifies why Dresselhaus coefficients extracted from two-dimensional
spin relaxation can differ from the cubic bulk coefficient and provides a useful framework for interpreting linear and cubic Dresselhaus parameters in
quantum wells.
Read the full abstract ▾
Materials Science · Cross-listed from cond-mat.supr-con
Pressure induced magnetic-field-free superconducting diode effect in NbSe2 flake
Shihao Zhu, Tian Le, Cuiying Pei et al. (+17 more)
The superconducting diode effect (SDE) is a fascinating nonreciprocal phenomenon where the critical current is different for opposite current directions. It is widely believed that realizing SDE requires breaking both inversion
symmetry (IS) and time-reversal
symmetry (TRS), which are usually achieved via
heterostructure engineering and applying external
magnetic fields. Here, we report a pressure-induced
magnetic-field-free SDE in NbSe2 flakes without any
heterostructures. We show that pressure alone breaks the IS, as confirmed by the second harmonic generation. Crucially, upon applying an out-of-plane
magnetic field (B), the SDE exhibits even-in-B behavior, implying the absence of explicit TRS breaking. This finding challenges the prevailing theoretical paradigm and demonstrates that a
magnetic-field-free SDE can emerge without explicitly breaking TRS. Thereby, our work establishes pressure engineering as a powerful tool for inducing nonreciprocal superconductivity and designing versatile,
magnetic-field-free superconducting devices.
Read the full abstract ▾
All authors Shihao Zhu, Tian Le, Cuiying Pei, Changhua Li, Yi Liao, Yi Zhao, Lingxiao Zhao, Qi Wang, Juefei Wu, Qilian Zhang, Yueshen Wu, Tonghuan Fu, Xujie Lü, Wenge Yang, Jie Shen, Jun Li, Yulin Chen, Xiao Lin, Wen-Yu He, Yanpeng Qi
Materials Science · Cross-listed from cond-mat.supr-con
Pressure-induced Superconductivity in Thermoelectric Semiconductor Mg3Sb2
Cuiying Pei, Yasong Wu, Airan Li et al. (+14 more)
The intrinsic electronic structures of narrow bandgap thermoelectric (TE) materials serve as a platform for the investigation of coupling effects of quasi-particles under high pressure, enabling the exploration of emerging electronic and
phonon transport, superconductivity, and topological transition. Here, we report the discovery of pressure-induced superconductivity in the TE
semiconductor Mg3Sb2. Upon the increased pressure, the metallization occurs at 8.7 GPa, followed by a superconducting transition concomitant with a carrier-type crossover from p- to n-type. This phenomenon arises from a pressure-induced structural phase transition from the semiconducting P-3m1 to the metallic C2/m-I phase. The superconducting critical temperature (Tc) exhibits a dome-shaped pressure dependence, peaking at 3.3 K at 12.6 GPa. Combined theoretical calculations, high-pressure Raman spectroscopy, and X-ray diffraction (XRD) measurements reveal an additional structural transition above 20 GPa, yielding a distinct C2/m-II phase. Our findings establish the high-pressure phase diagram of Mg3Sb2, elucidate its pressure-dependent electronic properties, and provide valuable insights for future investigations of TE materials under high pressure.
Read the full abstract ▾
All authors Cuiying Pei, Yasong Wu, Airan Li, Juefei Wu, Qi Wang, Yifan Zhu, Yi Zhao, Lingling Gao, Changhua Li, Weizheng Cao, Shihao Zhu, Mingxin Zhang, Yulin Chen, Chenguang Fu, Tiejun Zhu, Jiong Yang, Yanpeng Qi
Materials Science
Electrostatic Superlattices beyond 1:1 Stoichiometry
Binay P. Nayak, Prapti Kakkar, Wesley P. Korba et al. (+5 more)
Exotic nanoparticle superstructures can be accessed by harnessing nanoparticle softness and charge regulation, features often viewed as obstacles to structural control. Here, we show that regulated charge mismatch in
polymer-grafted nanoparticles enables the assembly of high-stoichiometry cubic superlattices. By co-tuning grafting density, particle size, and bulk composition, we realize ionic-
lattice analogues such as CaF2 and Th3P4, as well as single-component A3 and A7 superlattices without atomic counterparts. The A3
lattice has recently been identified theoretically as a photonic band-gap
lattice. These phases emerge from a 1:1 "parent"
lattice when local charge neutrality cannot be satisfied, driving either progressive interstitial filling or reorganization into a larger basis. For instance, the systematic occupation of ZnS tetrahedral sites yields CaF2, while ligand-swapping
symmetry breaking converts CsCl into Th3P4. Upon heating, the assemblies exhibit reversible
lattice contraction and pronounced negative thermal expansion. Furthermore, the energetic penalty for defects increases with nanoparticle size, facilitating the scalable production of high-quality, open superlattices for photonic applications.
Read the full abstract ▾
All authors Binay P. Nayak, Prapti Kakkar, Wesley P. Korba, Honghu Zhang, Wenjie Wang, Surya K. Mallapragada, Alex Travesset, David Vaknin
Materials Science
Optical properties of Ag, Au, and Cu from first principles
Xiao Zhang and Emmanouil Kioupakis
We present a comprehensive framework for investigating the optical response of metals from first principles that combines density functional theory, many-body perturbation theory, and efficient interpolation techniques based on maximally localized Wannier functions, and apply it to analyze the optical properties of silver (Ag), gold (Au), and copper (Cu). We evaluate the optical properties of these metallic materials considering both single-particle direct and
phonon-assisted excitations, as well as the resistive Drude contribution. We find an overall excellent agreement with experimental optical measurements for these materials, and show that both single-particle and collective excitations are important in capturing their optical response in the infrared. Our methodology provides fundamental understanding of the optical response of metals and is generally applicable to investigate the optoelectronic properties of emerging metallic materials.
Read the full abstract ▾