-
Competition for Survival and the Maximum Entropy Production Principle in Self-Organized Silver Particle Chains
Authors:
Albert Han,
Jiri Kataman-Kustwan,
Alexey Bezryadin
Abstract:
The maximum entropy production (MEP) principle is a hypothetical law of physics which dictates that complex systems, far from equilibrium, evolve into an ordered dissipative structure (DS) which generates as much entropy per second as possible. An important problem is whether the natural competition for resources, limits the ability of DS to achieve the maximum of the entropy production rate (EPR)…
▽ More
The maximum entropy production (MEP) principle is a hypothetical law of physics which dictates that complex systems, far from equilibrium, evolve into an ordered dissipative structure (DS) which generates as much entropy per second as possible. An important problem is whether the natural competition for resources, limits the ability of DS to achieve the maximum of the entropy production rate (EPR). We investigate this competition between DS by performing high precision electrical measurements on suspensions of silver particles under electric fields. To establish the impact of competition on MEP principle, precise electrical measurements are performed on two Ag suspension samples connected in parallel. The samples are able to self-organize, dissipate energy, generate entropy, and compete with each other for resources, i.e., electrical current. Our findings are as follows: (1) There is a competition between the two samples, which prevents both systems from achieving their maximum possible contribution to the global entropy production rate. (2) Due to this competition, we find that only one out of two samples can self-organize, while the other deteriorates and approaches zero EPR. (3) The global EPR, i.e., the entropy produced by the samples and the energy supply circuit, is also reduced from its possible maximum due to the competition between the sub-systems. Based on these observations, we propose that the competition effect constitutes an essential constraint that must be incorporated into formulations of the MEP. This principle parallels real-world phenomena, reflecting the competition for resources observed among species and individual organisms in natural systems. We also examine the global implications of the MEP and propose that it serves as a driving mechanism propelling the hypothetical ascent of civilizations along the Kardashev scale.
△ Less
Submitted 25 May, 2026;
originally announced May 2026.
-
Flexible Perovskite/Silicon Monolithic Tandem Solar Cells Approaching 30% Efficiency
Authors:
Yinqing Sun,
Faming Li,
Hao Zhang,
Wenzhu Liu,
Zenghui Wang,
Lin Mao,
Qian Li,
Youlin He,
Tian Yang,
Xianggang Sun,
Yicheng Qian,
Yinyi Ma,
Liping Zhang,
Junlin Du,
Jianhua Shi,
Guangyuan Wang,
Anjun Han,
Na Wang,
Fanying Meng,
Zhengxin Liu,
Mingzhen Liu
Abstract:
Thanks to their excellent properties of low cost, lightweight, portability, and conformity, flexible perovskite-based tandem solar cells show great potentials for energy harvesting applications, with flexible perovskite/c-silicon tandem solar cells particularly promising for achieving high efficiency. However, performance of flexible perovskite/c-silicon monolithic tandem solar cells still greatly…
▽ More
Thanks to their excellent properties of low cost, lightweight, portability, and conformity, flexible perovskite-based tandem solar cells show great potentials for energy harvesting applications, with flexible perovskite/c-silicon tandem solar cells particularly promising for achieving high efficiency. However, performance of flexible perovskite/c-silicon monolithic tandem solar cells still greatly lags, due to challenges in simultaneously achieving both efficient photocarrier transport and reliable mitigation of residual stress. Here, we reveal the critical role of perovskite phase homogeneity, for achieving high-efficient and mechanical-stable flexible perovskite/c-silicon heterojunction monolithic tandem solar cells (PSTs) with textured surface. Through ensuring high phase homogeneity, which promotes charge transfer across all facets of the pyramid on the textured substrates and releases the residual stress at the perovskite/c-silicon interface, we demonstrate flexible PSTs with a bending curvature of 0.44 cm-1, and a certified power conversion efficiency of 29.88% (1.04 cm2 aperture area), surpassing all other types of flexible perovskite-based photovoltaic devices. Our results can lead to broad applications and commercialization of flexible perovskite/c-silicon tandem photovoltaics.
△ Less
Submitted 29 April, 2025;
originally announced April 2025.
-
Abnormal Staebler-Wronski effect of amorphous silicon
Authors:
Wenzhu Liu,
Jianhua Shi,
Liping Zhang,
Anjun Han,
Shenglei Huang,
Xiaodong Li,
Jun Peng,
Yuhao Yang,
Yajun Gao,
Jian Yu,
Kai Jiang,
Xinbo Yang,
Zhenfei Li,
Junlin Du,
Xin Song,
Youlin Yu,
Zhixin Ma,
Yubo Yao,
Haichuan Zhang,
Lujia Xu,
Jingxuan Kang,
Yi Xie,
Hanyuan Liu,
Fanying Meng,
Frédéric Laquai
, et al. (2 additional authors not shown)
Abstract:
Great achievements in last five years, such as record-efficient amorphous/crystalline silicon heterojunction (SHJ) solar cells and cutting-edge perovskite/SHJ tandem solar cells, place hydrogenated amorphous silicon (a-Si:H) at the forefront of emerging photovoltaics. Due to the extremely low doping efficiency of trivalent boron (B) in amorphous tetravalent silicon, light harvesting of aforementio…
▽ More
Great achievements in last five years, such as record-efficient amorphous/crystalline silicon heterojunction (SHJ) solar cells and cutting-edge perovskite/SHJ tandem solar cells, place hydrogenated amorphous silicon (a-Si:H) at the forefront of emerging photovoltaics. Due to the extremely low doping efficiency of trivalent boron (B) in amorphous tetravalent silicon, light harvesting of aforementioned devices are limited by their fill factors (FF), which is a direct metric of the charge carrier transport. It is challenging but crucial to develop highly conductive doped a-Si:H for minimizing the FF losses. Here we report intensive light soaking can efficiently boost the dark conductance of B-doped a-Si:H "thin" films, which is an abnormal Staebler-Wronski effect. By implementing this abnormal effect to SHJ solar cells, we achieve a certificated power conversion efficiency (PCE) of 25.18% (26.05% on designated area) with FF of 85.42% on a 244.63-cm2 wafer. This PCE is one of the highest reported values for total-area "top/rear" contact silicon solar cells. The FF reaches 98.30 per cent of its Shockley-Queisser limit.
△ Less
Submitted 3 June, 2021;
originally announced June 2021.
-
Unveiling Defect-Mediated Carrier Dynamics in Monolayer Semiconductors by Spatiotemporal Microwave Imaging
Authors:
Zhaodong Chu,
Chun-Yuan Wang,
Jiamin Quan,
Chenhui Zhang,
Chao Lei,
Ali Han,
Xuejian Ma,
Hao-Ling Tang,
Dishan Abeysinghe,
Matthew Staab,
Xixiang Zhang,
Allan H. MacDonald,
Vincent Tung,
Xiaoqin Li,
Chih-Kang Shih,
Keji Lai
Abstract:
The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of defects in the materials, which are not necessarily detrimental for certain applications. For instance, defects can lead to an enhanced photoconduction, a complicated process involving charge generation and recombination in the time domain and carrier transport in the spat…
▽ More
The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of defects in the materials, which are not necessarily detrimental for certain applications. For instance, defects can lead to an enhanced photoconduction, a complicated process involving charge generation and recombination in the time domain and carrier transport in the spatial domain. Here, we report the simultaneous spatial and temporal photoconductivity imaging in two types of WS2 monolayers by laser-illuminated microwave impedance microscopy. The diffusion length and carrier lifetime were directly extracted from the spatial profile and temporal relaxation of microwave signals respectively. Time-resolved experiments indicate that the critical process for photo-excited carriers is the escape of holes from trap states, which prolongs the apparent lifetime of mobile electrons in the conduction band. As a result, counterintuitively, the photoconductivity is stronger in CVD samples than exfoliated monolayers with a lower defect density. Our work reveals the intrinsic time and length scales of electrical response to photo-excitation in van der Waals materials, which is essential for their applications in novel optoelectronic devices.
△ Less
Submitted 3 March, 2020;
originally announced March 2020.
-
Energy-resolved Photoconductivity Mapping in a Monolayer-bilayer WSe2 Lateral Heterostructure
Authors:
Zhaodong Chu,
Ali Han,
Chao Lei,
Sergei Lopatin,
Peng Li,
David Wannlund,
Di Wu,
Kevin Herrera,
Xixiang Zhang,
Allan H. MacDonald,
Xiaoqin Li,
Lain-Jong Li,
Keji Lai
Abstract:
Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band structure engineering. Since electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we re…
▽ More
Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band structure engineering. Since electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we report the spatial mapping of photoconductivity in a monolayer-bilayer WSe2 lateral heterostructure under multiple excitation lasers. As the photon energy increases, the light-induced conductivity detected by microwave impedance microscopy first appears along the hetero-interface and bilayer edge, then along the monolayer edge, inside the bilayer area, and finally in the interior of the monolayer region. The sequential emergence of mobile carriers in different sections of the sample is consistent with the theoretical calculation of local energy gaps. Quantitative analysis of the microscopy and transport data also reveals the linear dependence of photoconductivity on the laser intensity and the influence of interlayer coupling on carrier recombination. Combining theoretical modeling, atomic scale imaging, mesoscale impedance microscopy, and device-level characterization, our work suggests an exciting perspective to control the intrinsic band-gap variation in 2D heterostructures down to the few-nanometer regime.
△ Less
Submitted 9 October, 2018;
originally announced October 2018.
-
A method for mechanical generation of radio frequency fields in nuclear magnetic resonance force microscopy
Authors:
J. J. T. Wagenaar,
A. M. J. den Haan,
R. J. Donkersloot,
F. Marsman,
M. de Wit,
L. Bossoni,
T. H. Oosterkamp
Abstract:
We present an innovative method for magnetic resonance force microscopy (MRFM) with ultra-low dissipation, by using the higher modes of the mechanical detector as radio frequency (rf) source. This method allows MRFM on samples without the need to be close to an rf source. Furthermore, since rf sources require currents that give dissipation, our method enables nuclear magnetic resonance experiments…
▽ More
We present an innovative method for magnetic resonance force microscopy (MRFM) with ultra-low dissipation, by using the higher modes of the mechanical detector as radio frequency (rf) source. This method allows MRFM on samples without the need to be close to an rf source. Furthermore, since rf sources require currents that give dissipation, our method enables nuclear magnetic resonance experiments at ultra-low temperatures. Removing the need for an on-chip rf source is an important step towards a MRFM which can be widely used in condensed matter physics.
△ Less
Submitted 19 September, 2016;
originally announced September 2016.
-
Probing the Nuclear Spin-Lattice Relaxation Time at the Nanoscale
Authors:
J. J. T. Wagenaar,
A. M. J. den Haan,
J. M. de Voogd,
L. Bossoni,
T. A. de Jong,
M. de Wit,
K. M. Bastiaans,
D. J. Thoen,
A. Endo,
T. M. Klapwijk,
J. Zaanen,
T. H. Oosterkamp
Abstract:
Nuclear spin-lattice relaxation times are measured on copper using magnetic resonance force microscopy performed at temperatures down to 42 mK. The low temperature is verified by comparison with the Korringa relation. Measuring spin-lattice relaxation times locally at very low temperatures opens up the possibility to measure the magnetic properties of inhomogeneous electron systems realized in oxi…
▽ More
Nuclear spin-lattice relaxation times are measured on copper using magnetic resonance force microscopy performed at temperatures down to 42 mK. The low temperature is verified by comparison with the Korringa relation. Measuring spin-lattice relaxation times locally at very low temperatures opens up the possibility to measure the magnetic properties of inhomogeneous electron systems realized in oxide interfaces, topological insulators and other strongly correlated electron systems such as high-Tc superconductors.
△ Less
Submitted 27 June, 2016; v1 submitted 14 March, 2016;
originally announced March 2016.
-
On the nature of wettability of van der Waals heterostructures
Authors:
Meenakshi Annamalai,
Kalon Gopinadhan,
Sang A Han,
Surajit Saha,
Hye Jeong Park,
Eun Bi Cho,
Brijesh Kumar,
Sang-Woo Kim,
T Venkatesan
Abstract:
Wetting behaviour of surfaces is believed to be affected by van der Waals (vdW) forces, however, there is no clear demonstration of this. With the isolation of two-dimensional vdW layered materials it is possible to test this hypothesis. In this paper, we report the wetting behaviour of vdW heterostructures which include, chemical vapor deposition (CVD) grown graphene, molybdenum disulfide (MoS2)…
▽ More
Wetting behaviour of surfaces is believed to be affected by van der Waals (vdW) forces, however, there is no clear demonstration of this. With the isolation of two-dimensional vdW layered materials it is possible to test this hypothesis. In this paper, we report the wetting behaviour of vdW heterostructures which include, chemical vapor deposition (CVD) grown graphene, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) on few layers of hexagon boron nitride (h-BN) and SiO2/Si. Our study clearly shows that while this class of two-dimensional materials are not wetting transparent, there seems to be a significant amount of influence on their wetting properties by the underlying substrate due to dominant vdW forces. Contact angle measurements indicate that graphene and graphene-like layered transitional metal dichalcogenides invariably have intrinsically dispersive surfaces with a dominating London-vdW force-mediated wettability. Electric field controlled wetting studies of MoS2/WS2/SiO2/Si heterostructures were performed and no notable changes to the water contact angle was seen with applied voltage although two orders of magnitude change in resistance was observed. We postulate that the highly dispersive nature of these surfaces arising from the predominant London-vdW forces could be the reason for such observation.
△ Less
Submitted 13 December, 2015;
originally announced December 2015.
-
Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures
Authors:
A. M. J. den Haan,
J. J. T. Wagenaar,
J. M. de Voogd,
G. Koning,
T. H. Oosterkamp
Abstract:
We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to $25$ mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a…
▽ More
We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to $25$ mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a $3.43$ $μ$m-diameter magnetic particle attached to an ultrasoft cantilever, and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time $T_1=0.39\pm0.08$ ms and spin density $σ=0.14\pm0.01$ spins per nm$^2$. Our analysis shows that at temperatures $\leq500$ mK magnetic dissipation is an important source of non-contact friction.
△ Less
Submitted 21 January, 2016; v1 submitted 3 September, 2015;
originally announced September 2015.
-
Probing the magnetic moment of FePt micromagnets prepared by Focused Ion Beam milling
Authors:
H. C. Overweg,
A. M. J. den Haan,
H. J. Eerkens,
P. F. A. Alkemade,
A. L. La Rooij,
R. J. C. Spreeuw,
L. Bossoni,
T. H. Oosterkamp
Abstract:
We investigate the degradation of the magnetic moment of a 300 nm thick FePt film induced by Focused Ion Beam (FIB) milling. A $1~μ\mathrm{m} \times 8~μ\mathrm{m}$ rod is milled out of a film by a FIB process and is attached to a cantilever by electron beam induced deposition. Its magnetic moment is determined by frequency-shift cantilever magnetometry. We find that the magnetic moment of the rod…
▽ More
We investigate the degradation of the magnetic moment of a 300 nm thick FePt film induced by Focused Ion Beam (FIB) milling. A $1~μ\mathrm{m} \times 8~μ\mathrm{m}$ rod is milled out of a film by a FIB process and is attached to a cantilever by electron beam induced deposition. Its magnetic moment is determined by frequency-shift cantilever magnetometry. We find that the magnetic moment of the rod is $μ= 1.1 \pm 0.1 \times 10 ^{-12} \mathrm{Am}^2$, which implies that 70% of the magnetic moment is preserved during the FIB milling process. This result has important implications for atom trapping and magnetic resonance force microscopy (MRFM), that are addressed in this paper.
△ Less
Submitted 23 August, 2015; v1 submitted 27 April, 2015;
originally announced April 2015.
-
Pulsed Adiabatic Photoassociation via Scattering Resonances
Authors:
Alex C. Han,
Evgeny A. Shapiro,
Moshe Shapiro
Abstract:
We develop the theory for the Adiabatic Raman Photoassociation (ARPA) of ultracold atoms to form ultracold molecules in the presence of scattering resonances. Based on a computational method in which we replace the continuum with a discrete set of "effective modes", we show that the existence of resonances greatly aids in the formation of deeply bound molecular states. We illustrate our general th…
▽ More
We develop the theory for the Adiabatic Raman Photoassociation (ARPA) of ultracold atoms to form ultracold molecules in the presence of scattering resonances. Based on a computational method in which we replace the continuum with a discrete set of "effective modes", we show that the existence of resonances greatly aids in the formation of deeply bound molecular states. We illustrate our general theory by computationally studying the formation of $^{85}$Rb$_2$ molecules from pairs of colliding ultracold $^{85}$Rb atoms. The single-event transfer yield is shown to have a near-unity value for wide resonances, while the ensemble-averaged transfer yield is shown to be higher for narrow resonances. The ARPA yields are compared with that of (the experimentally measured) "Feshbach molecule" magneto-association. Our findings suggest that an experimental investigation of ARPA at sub-$μ$K temperatures is warranted.
△ Less
Submitted 20 June, 2011; v1 submitted 8 April, 2011;
originally announced April 2011.