Showing 1–13 of 13 results for author: Ning, Y

Long-range orbital transport and inverse orbital Hall effect in Co/Ru-based terahertz emitters

Authors: Zhou Chao, Zhang Shaohua, Hao Lei, Jin Yaxuan, Jiang Xianguo, Yang Ning, Zheng Li, Meng Hao, Lu Chao, Huang Wendeng, Wu Yizheng, Zhou Yan, Jia Xu

Abstract: The utilization of terahertz (THz) emission spectroscopy in femtosecond photoexcited spintronic heterostructures has emerged as a versatile tool for investigating ultrafast spin-transport in a noncontact and non-invasive manner. However, the investigation of ultrafast orbital-transport is still in the primitive stage. Here, we experimentally demonstrate the orbital-to-charge current conversion in… ▽ More The utilization of terahertz (THz) emission spectroscopy in femtosecond photoexcited spintronic heterostructures has emerged as a versatile tool for investigating ultrafast spin-transport in a noncontact and non-invasive manner. However, the investigation of ultrafast orbital-transport is still in the primitive stage. Here, we experimentally demonstrate the orbital-to-charge current conversion in Co/Ru heterostructures. Time-domain measurements reveal delayed and broadened terahertz waveforms with increasing Ru thickness, consistent with long-range orbital transport. In Co/Pt/Ru trilayers, the terahertz emission is further enhanced through constructive interference between the inverse spin Hall effect (ISHE) in Pt and inverse orbital Hall effect (IOHE) in Ru, while reversed stack structures show suppressed output. Ferromagnetic resonance (FMR) measurements reveal a strong correlation between damping and THz amplitude, highlighting efficient angular momentum conversion. These results position Co/Ru as a promising orbitronic platform for tunable ultrafast THz emission. Our results not only strengthen the physical mechanism of condensed matter physics but also pave the way for designing promising spin-orbitronic devices and terahertz emitters. △ Less

Submitted 3 February, 2026; originally announced February 2026.

Comments: 22 pages, 5 figures

Checkerboard-type Zhang-Rice States in Overdoped Cuprate Superconductors

Authors: Xiongfang Liu, Kun Han, Yan Peng, Yuanjie Ning, Jing Wu, Zhaoyang Luo, Difan Zhou, Zhigang Zeng, Qian He, Chuanbing Cai, Mark. B. H. Breese, Ariando Ariando, Chi Sin Tang, George A. Sawatzky, Mi Jiang, Xinmao Yin

Abstract: Cuprate superconductors remain central to condensed matter physics due to their technological relevance and unconventional, incompletely understood electronic behavior. While the canonical phase diagram and low-energy models have been shaped largely by studies of underdoped and moderately doped cuprates, the overdoped regime has received comparatively limited attention.Here, we track the evolution… ▽ More Cuprate superconductors remain central to condensed matter physics due to their technological relevance and unconventional, incompletely understood electronic behavior. While the canonical phase diagram and low-energy models have been shaped largely by studies of underdoped and moderately doped cuprates, the overdoped regime has received comparatively limited attention.Here, we track the evolution of the electronic structure from optimal to heavy overdoping in La2-xSrxCuO4(LSCO) using broadband optical spectroscopy across x=0.15-0.60. The measured spectral changes--including the redistribution of Zhang-Rice-related spectral weigh--are in qualitative agreement with determinant quantum Monte Carlo simulations of the three-orbital Emery model, which together indicate a pronounced reconstruction of the electronic structure beyond hole concentrations x>0.2. Guided by these observations, we propose a spontaneous checkerboard-type Zhang-Rice electronic configuration that captures the coexistence of itinerant and localized carriers characteristic of the heavily overdoped state. Our results refine the doping-dependent Zhang-Rice-based framework for cuprates, illuminate how correlations persist deep into the overdoped regime, and provide new constraints on microscopic mechanisms of high-temperature superconductivity, with broader implications for correlated transition-metal oxides. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Atomistic understanding of hydrogen bubble-induced embrittlement in tungsten enabled by machine learning molecular dynamics

Authors: Yu Bao, Keke Song, Jiahui Liu, Yanzhou Wang, Yifei Ning, Penghua Ying, Ping Qian

Abstract: Hydrogen bubble formation within nanoscale voids is a critical mechanism underlying the embrittlement of metallic materials, yet its atomistic origins remains elusive. Here, we present an accurate and transferable machine-learned potential (MLP) for the tungsten-hydrogen binary system within the neuroevolution potential (NEP) framework, trained through active learning on extensive density function… ▽ More Hydrogen bubble formation within nanoscale voids is a critical mechanism underlying the embrittlement of metallic materials, yet its atomistic origins remains elusive. Here, we present an accurate and transferable machine-learned potential (MLP) for the tungsten-hydrogen binary system within the neuroevolution potential (NEP) framework, trained through active learning on extensive density functional theory data. The developed NEP-WH model reproduces a wide range of lattice and defect properties in tungsten systems, as well as hydrogen solubility, with near first-principles accuracy, while retaining the efficiency of empirical potentials. Crucially, it is the first MLP capable of capturing hydrogen trapping and H\textsubscript{2} formation in nanovoids, with quantitative fidelity. Large-scale machine-learning molecular dynamics simulations reveal a distinct aggregation pathway where planar hydrogen clusters nucleate and grow along \{100\} planes near voids, with hexagonal close-packed structures emerging at their intersections. Under uniaxial tension, these aggregates promote bubble fracture and the development of regular \{100\} cracks, suppressing dislocation activity and resulting in brittle fracture behavior. This work provides detailed atomistic insights into hydrogen bubble evolution and fracture in nanovoids, enables predictive modeling of structural degradation in extreme environments, and advances fundamental understanding of hydrogen-induced damage in structural metals. △ Less

Submitted 27 August, 2025; originally announced August 2025.

Comments: 14pages,7 figures

Journal ref: npj Computational Materials,12,108 (2026)

Contrasting magnetism in VPS3 and CrI3 monolayers with the common honeycomb S = 3/2 spin lattice

Authors: Ke Yang, Yueyue Ning, Yaozhenghang Ma, Yuxuan Zhou, Hua Wu

Abstract: Two-dimensional (2D) magnetic materials are promising candidates for spintronics and quantum technologies. One extensively studied example is the ferromagnetic (FM) CrI$_3$ monolayer with the honeycomb Cr$^{3+}$ ($t_{2g}^3$, $S$ = 3/2) spin lattice, while VPS$_3$ has a same honeycomb $S$ = 3/2 spin lattice (V$^{2+}$, $t_{2g}^3$) but displays N$\acute{e}$el antiferromagnetism (AFM). In this work, w… ▽ More Two-dimensional (2D) magnetic materials are promising candidates for spintronics and quantum technologies. One extensively studied example is the ferromagnetic (FM) CrI$_3$ monolayer with the honeycomb Cr$^{3+}$ ($t_{2g}^3$, $S$ = 3/2) spin lattice, while VPS$_3$ has a same honeycomb $S$ = 3/2 spin lattice (V$^{2+}$, $t_{2g}^3$) but displays N$\acute{e}$el antiferromagnetism (AFM). In this work, we study the electronic structure and particularly the contrasting magnetism of VPS$_3$ and CrI$_3$ monolayers. We find that VPS$_3$ is a Mott-Hubbard insulator but CrI$_3$ is a charge-transfer insulator, and therefore their magnetic exchange mechanisms are essentially different. The first nearest-neighbor (1NN) direct $d$-$d$ exchange dominates in VPS$_3$, thus leading to a strong antiferromagnetic (AF) coupling. However, the formation of vanadium vacancies, associated with instability of the low-valence V$^{2+}$ ions, suppresses the AF coupling and thus strongly reduces the N$\acute{e}$el temperature ($T_{\text{N}}$) in line with the experimental observation. In contrast, our results reveal that the major 1NN $d$-$p$-$d$ superexchanges in CrI$_3$ via different channels give rise to competing FM and AF couplings, ultimately resulting in a weak FM coupling as observed experimentally. After revisiting several important superexchange channels reported in the literature, based on our MLWFs and tight-binding analyses, we note that some antiphase contributions must be subtly and simultaneously considered, and thus we provide a deeper insight into the FM coupling of CrI$_3$. Moreover, we identify and compare the major contributions to the magnetic anisotropy, i.e., a weak shape anisotropy in VPS$_3$ and a relatively strong exchange anisotropy in CrI$_3$. △ Less

Submitted 8 April, 2025; originally announced April 2025.

Comments: 16 pages, 12 figures, 3 tables

Journal ref: Phys. Rev. B 111, 134421 (2025)

Understanding the Ising zigzag antiferromagnetism of FePS3 and FePSe3 monolayers

Authors: Ke Yang, Yueyue Ning, Yuxuan Zhou, Di Lu, Yaozhenghang Ma, Lu Liu, Shengli Pu, Hua Wu

Abstract: This study investigates the spin-orbital states of FePS3 and FePSe3 monolayers and the origin of their Ising zigzag AFM, using DFT, crystal field level diagrams, superexchange analyses, and parallel tempering MC simulations. Our calculations show that under the trigonal elongation of the FeS6 (FeSe6) octahedra, the $e_g^π$ doublet of the Fe 3d crystal field levels lies lower than the $a_{1g}$ sing… ▽ More This study investigates the spin-orbital states of FePS3 and FePSe3 monolayers and the origin of their Ising zigzag AFM, using DFT, crystal field level diagrams, superexchange analyses, and parallel tempering MC simulations. Our calculations show that under the trigonal elongation of the FeS6 (FeSe6) octahedra, the $e_g^π$ doublet of the Fe 3d crystal field levels lies lower than the $a_{1g}$ singlet by about 108 meV (123 meV), which is much larger than the strength of Fe 3d SOC. Then, the half-filled minority-spin $e_g^π$ doublet of the high-spin Fe$^{2+}$ ions ($d^{5\uparrow,1\downarrow}$) splits by the SOC into the lower $L_{z+}$ and higher $L_{z-}$ states. The spin-orbital ground state $d^{5\uparrow}$$L_{z+}^{1\downarrow}$ formally with $S_z$ = 2 and $L_z$ = 1 gives the large z-axis spin/orbital moments of 3.51/0.76 $μ_{B}$ (3.41/0.67 $μ_{B}$) for FePS$_3$ (FePSe$_3$) monolayer, and both the moments are reduced by the strong (stronger) Fe 3d hybridizations with S 3p (Se 4p) states. As a result, FePS3 (FePSe3) monolayer has a huge perpendicular single-ion anisotropy energy of 19.4 meV (14.9 meV), giving an Ising-type magnetism. Moreover, via the maximally localized Wannier functions, we find that the first nearest neighboring (1NN) Fe-Fe pair has large hopping parameters in between some specific orbitals, and so does the 3NN Fe-Fe pair. In contrast, the 2NN Fe-Fe pair has much smaller hopping parameters and the 4NN Fe-Fe pair has negligibly small ones. Then, a combination of those hopping parameters and the superexchange picture can readily explain the computed strong 1NN ferromagnetic coupling and the strong 3NN antiferromagnetic one but the relatively much smaller 2NN antiferromagnetic coupling. Furthermore, our PTMC simulations give TN of 119 K for FePS3 monolayer and also predict for FePSe3 monolayer the same magnetic structure with a close or even higher TN. △ Less

Submitted 23 July, 2024; originally announced July 2024.

Comments: 14 pages, 9 figures, 3 tables

Journal ref: Phys. Rev. B 110, 024427 (2024)

Unraveling Anisotropic Hybridizations of Solid-state Electrolyte Nano-films in Li-ion Batteries

Authors: Yuanjie Ning, Wenjun Wu, Liang Dai, Shuo Sun, Zhigang Zeng, Dengsong Zhang, Mark B. H. Breese, Chuanbing Cai, Chi Sin Tang, Xinmao Yin

Abstract: Li2WO4 (LWO) is recognized for its potential as a solid-state electrolyte and it has demonstrated the ability to enhance the electrochemical performance of LiCoO2 (LCO) cathodes in Li-ion batteries. However, prior investigations into LWO have predominantly involved polycrystalline structures, thereby lacking a comprehensive understanding of its behavior when interfaced with single crystal systems,… ▽ More Li2WO4 (LWO) is recognized for its potential as a solid-state electrolyte and it has demonstrated the ability to enhance the electrochemical performance of LiCoO2 (LCO) cathodes in Li-ion batteries. However, prior investigations into LWO have predominantly involved polycrystalline structures, thereby lacking a comprehensive understanding of its behavior when interfaced with single crystal systems, particularly those intricately connected to LCO. In this study, we employ pulsed laser deposition (PLD) to epitaxially synthesize LWO nano-films on LCO layers with different orientations. Based on a series of high-resolution synchrotron-based techniques including X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), the electronic structure of LWO is carefully scrutinized where a higher main energy level of W5d(eg)-O2p orbitals hybridization in LWO/LCO(104) as compared to LWO/LCO(003) has been observed. This experimental finding is further validated by a comprehensive set of density of states calculations. Furthermore, detailed polarized XAS characterization unveils distinct anisotropy between the two oriented LWO configurations. This comprehensive scientific investigation, harnessing the capabilities of synchrotron-based techniques, provides invaluable insights for future studies, offering guidance for the optimized utilization of LWO as a solid-state electrolyte or modification layer for LCO cathodes in high-powered Li-ion batteries. △ Less

Submitted 12 May, 2024; originally announced May 2024.

Comments: 8 pages, 5 figures

FeS2 monolayer: a high valence and high-$T_{\rm C}$ Ising ferromagnet

Authors: Ke Yang, Yaozhenghang Ma, Lu Liu, Yueyue Ning, Di Lu, Yuxuan Zhou, Zhongyao Li, Hua Wu

Abstract: Two-dimensional (2D) magnetic materials are of current great interest for their promising applications in spintronics. Strong magnetic coupling and anisotropy are both highly desirable for the achievement of a high temperature magnetic order. Here we propose the unusual high valent FeS$_2$ hexagonal monolayer as such a candidate for a strong Ising 2D ferromagnet (FM), by spin-orbital state analyse… ▽ More Two-dimensional (2D) magnetic materials are of current great interest for their promising applications in spintronics. Strong magnetic coupling and anisotropy are both highly desirable for the achievement of a high temperature magnetic order. Here we propose the unusual high valent FeS$_2$ hexagonal monolayer as such a candidate for a strong Ising 2D ferromagnet (FM), by spin-orbital state analyses, first-principles calculations, and the renormalized spin-wave theory (RSWT). We find that very importantly, the high valent Fe$^{4+}$ ion is in the low-spin state ($t_{2g}^{4}$, $S$=1) with degenerate $t_{2g}$ orbitals rather than the high-spin state ($t_{2g}^{3}e_g^{1}$, $S$=2). It is the low-spin state that allows to carry a large perpendicular orbital moment and then produces a huge single ion anisotropy (SIA) of 25 meV/Fe. Moreover, the negative charge transfer character associated with the unusual high valence, strong Fe $3d$-S $3p$ hybridization, wide bands, and a small band gap all help to establish a strong superexchange. Indeed, our first-principles calculations confirm the strong FM superexchange and the huge perpendicular SIA, both of which are further enhanced by a compressive strain. Then, our RSWT calculations predict that the FM $T_{\rm C}$ is 261 K for the pristine FeS$_2$ monolayer and could be increased to 409 K under the compressive --5\% strain. The high $T_{\rm C}$ is also reproduced by our Monte Carlo (MC) simulations. Therefore, it is worth exploring the high-$T_{\rm C}$ Ising FMs in the high valent 2D magnetic materials with degenerate orbitals. △ Less

Submitted 11 January, 2024; originally announced January 2024.

Comments: 13 pages, 5 figures

Journal ref: Phys. Rev. B 109, 014431 (2024)

Small polarons mediated near-room-temperature metal-insulator transition in vanadium dioxide and their hopping dynamics

Authors: Xiongfang Liu, Tong Yang, Shanquan Chen, Jing Wu, Chi Sin Tang, Yuanjie Ning, Zuhuang Chen, Liang Dai, Mengxia Sun, Mingyao Chen, Kun Han, Difan Zhou, Shengwei Zeng, Shuo Sun, Sensen Li, Ming Yang, Mark B. H. Breese, Chuanbing Cai, Thirumalai Venkatesan, Andrew T. S. Wee, Xinmao Yin

Abstract: Researchers pursuing advanced photoelectric devices have discovered near room-temperature metal-insulator transitions (MIT) in non-volatile VO2. Despite theoretical investigations suggesting that polaron dynamics mediate the MIT, direct experimental evidence remains scarce. In this study, we present direct evidence of the polaron state in insulating VO2 through high-resolution spectroscopic ellips… ▽ More Researchers pursuing advanced photoelectric devices have discovered near room-temperature metal-insulator transitions (MIT) in non-volatile VO2. Despite theoretical investigations suggesting that polaron dynamics mediate the MIT, direct experimental evidence remains scarce. In this study, we present direct evidence of the polaron state in insulating VO2 through high-resolution spectroscopic ellipsometry measurements and first-principles calculations. We illustrate the complementary role of polaron dynamics in facilitating Peierls and Mott transitions, thereby contributing to the MIT processes. Furthermore, our observations and characterizations of conventional metallic and correlated plasmons in the respective phases of the VO2 film offer valuable insights into their electron structures. This investigation enhances comprehension of the MIT mechanism in correlated systems and underscores the roles of polarons, lattice distortions, and electron correlations in facilitating phase transition processes in strongly-correlated systems. Additionally, the detailed detection of small polarons and plasmons serves as inspiration for the development of new device functionalities. △ Less

Submitted 22 January, 2025; v1 submitted 28 December, 2023; originally announced December 2023.

Comments: Research article

Journal ref: Applied Physics Reviews. 12, 011403 (2025)

Exploration of the two-dimensional Ising magnetic materials in the triangular prismatic crystal field

Authors: Shuhang Chen, Wenjing Xu, Yueyue Ning, Ke Yang

Abstract: Magnetic anisotropy is essential for stabilizing two-dimensional (2D) magnetism, which has significant applications in spintronics and the advancement of fundamental physics. In this work, we examine the electronic structure and magnetic properties of triangular prismatic MSi$_2$N$_4$ (M = V, Cr) monolayers, using crystal field theory, spin-orbital state analyses, and density functional calculatio… ▽ More Magnetic anisotropy is essential for stabilizing two-dimensional (2D) magnetism, which has significant applications in spintronics and the advancement of fundamental physics. In this work, we examine the electronic structure and magnetic properties of triangular prismatic MSi$_2$N$_4$ (M = V, Cr) monolayers, using crystal field theory, spin-orbital state analyses, and density functional calculations. Our results reveal that the pristine VSi$_2$N$_4$ monolayer exhibits magnetism with a V$^{4+}$ 3$d^1$ $S$ = 1/2 charge-spin state within the triangular prismatic crystal field. However, the strong $d$ orbital hybridization between adjacent V$^{4+}$ ions disrupts the $d$ orbital splitting in this crystal field, resulting in a relatively small in-plane magnetic anisotropy of approximately 2 $μ$eV per V atom.In contrast, the pristine CrSi$_2$N$_4$ monolayer is nonmagnetic, characterized by the Cr$^{4+}$ 3$d^2$ $S$ = 0 state. Upon substituting nonmagnetic Cr$^{4+}$ with Si$^{4+}$, Cr$_\frac{1}{3}$Si$_\frac{8}{3}$N$_4$ transforms into an antiferromagnetic insulator with Cr$^{4+}$ 3$d^2$ $S$ = 1 state, featuring a large orbital moment of -1.06 $μ_{\rm B}$ oriented along the $z$-axis and huge perpendicular magnetic anisotropy of 18.63 meV per Cr atom. These findings highlight the potential for further exploration of 2D Ising magnetic materials within a unique triangular prismatic crystal field. △ Less

Submitted 25 December, 2023; originally announced December 2023.

Journal ref: The Journal of Physical Chemistry C 2024, 128, 1, 556-562

Intermodulation distortion of actuated MEMS capacitive switches

Authors: Xi Luo, Yaqing Ning, David Molinero, Cristiano Palego, James CM Hwang, Charles L Goldsmith

Abstract: For the first time, intermodulation distortion of micro-electromechanical capacitive switches in the actuated state was analyzed both theoretically and experimentally. The distortion, although higher than that of switches in the suspended state, was found to decrease with increasing bias voltage but to depend weakly on modulation frequencies between 55 kHz and 1.1 MHz. This dependence could be exp… ▽ More For the first time, intermodulation distortion of micro-electromechanical capacitive switches in the actuated state was analyzed both theoretically and experimentally. The distortion, although higher than that of switches in the suspended state, was found to decrease with increasing bias voltage but to depend weakly on modulation frequencies between 55 kHz and 1.1 MHz. This dependence could be explained by the orders-of-magnitude increase of the spring constant when the switches were actuated. Additionally, the analysis suggested that increasing the spring constant and decreasing the contact roughness could improve the linearity of actuated switches. These results are critical to micro-electromechanical capacitive switches used in tuners, filters, phase shifters, etc. where the linearity of both suspended and actuated states are critical. △ Less

Submitted 18 July, 2017; originally announced July 2017.

Journal ref: Microwave Measurement Conference (ARFTG), 2013 81st ARFTG

Tunneling induced dark states and controllable fluorescence spectrum in quantum-dot molecules

Authors: Si-Cong Tian, Ren-Gang Wan, Cun-Zhu Tong, Yong-Qiang Ning, Li-Jun Wang

Abstract: We theoretically investigate the spectrum of the fluorescence from triple quantum-dot molecules and demonstrate that it is possible to use tunneling to induce dark states. Unlike the atomic system, in quantum-dot molecules we can use tunneling to create the dark states and control fluorescence emission, requiring no coupling lasers. And interesting features such as quenching and narrowing of the f… ▽ More We theoretically investigate the spectrum of the fluorescence from triple quantum-dot molecules and demonstrate that it is possible to use tunneling to induce dark states. Unlike the atomic system, in quantum-dot molecules we can use tunneling to create the dark states and control fluorescence emission, requiring no coupling lasers. And interesting features such as quenching and narrowing of the fluorescence can be obtained. We also explain the spectrum with the transition properties of the dressed states generated by the coupling of the laser and the two tunneling. The quenching of the fluorescence is due to the tunneling induced dark states, while the narrowing of the central peak is due to the slow decay rate of the dressed levels. △ Less

Submitted 12 November, 2013; originally announced November 2013.

Effects of spontaneously generated coherence on resonance fluorescence from lateral triple quantum -dot molecules

Authors: Si-Cong Tian, Cun-Zhu Tong, Chun-Liang Wang, Yong-Qiang Ning, Li-Jun Wang

Abstract: We investigate the spectrum of the resonance fluorescence from the lateral triple quantum dots controlled by voltage and obtain some interesting features such as controllable triple narrow peaks. In our system we use tunneling instead of coupling lasers, and the positions, widths and heights of the resonance fluorescence peaks can be controlled by tuning the tunneling couplings. We explain the obs… ▽ More We investigate the spectrum of the resonance fluorescence from the lateral triple quantum dots controlled by voltage and obtain some interesting features such as controllable triple narrow peaks. In our system we use tunneling instead of coupling lasers, and the positions, widths and heights of the resonance fluorescence peaks can be controlled by tuning the tunneling couplings. We explain the observed spectrum with the transition properties of the dressed states generated by the coupling of the two tunneling and the laser field. These features can also be viewed as the effects of Spontaneously Generated Coherence between the close-lying levels in the dressed state picture of the tunneling couplings. And the scheme proposed here can permit the observation of Spontaneously Generated Coherence. △ Less

Submitted 17 October, 2013; originally announced October 2013.

Tunneling induced transparency and controllable group velocity in triple and multiple quantum-dot molecules

Authors: Si-Cong Tian, Cun-Zhu Tong, Ren-Gang Wan, Yong-Qiang Ning, Li-Jun Wang

Abstract: We analyze the interaction of a triple quantum dot molecules controlled by the tunneling coupling instead of coupling laser. A general analytic expression for the steady-state linear susceptibility for a probe-laser field is obtained and we show that the system can exhibit two transparency windows. The group velocity of the probe-laser pulse is also analyzed. By changing the tunneling couplings, t… ▽ More We analyze the interaction of a triple quantum dot molecules controlled by the tunneling coupling instead of coupling laser. A general analytic expression for the steady-state linear susceptibility for a probe-laser field is obtained and we show that the system can exhibit two transparency windows. The group velocity of the probe-laser pulse is also analyzed. By changing the tunneling couplings, two laser pulses with different central frequency can propagate with the same group velocity. And the group velocity can be as low as 300 m/s in our system. We extend our analysis to the case of multiple quantum dot molecules (the number of the quantum dots is N) and show that the system can exhibit at most N-1 transparency windows. And at most N-1 laser pulses with different central frequencies can be slowed down. △ Less

Submitted 17 October, 2013; originally announced October 2013.