Search query: Nonreciprocal charge transport up to room

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abstract: Nonmagnetic Rashba systems with broken inversion symmetry are expected to exhibit nonreciprocal charge transport, a new paradigm of unidirectional magnetoresistance in the absence of ferromagnetic layer. So far, most work on nonreciprocal transport has been solely limited to cryogenic temperatures, which is a major obstacle for exploiting the room temperature two terminal devices based on such a nonreciprocal response. Here, we report a nonreciprocal charge transport behavior up to room temperature in semiconductor a GeTe with coexisting the surface and bulk Rashba states. The combination of the band structure measurements and theoretical calculations strongly suggest that the nonreciprocal response is ascribed to the giant bulk Rashba spin splitting rather than the surface Rashba states. Remarkably, we find that the magnitude of the nonreciprocal response shows an unexpected non monotonical dependence on temperature. The extended theoretical model based on the second order spin orbit coupled magnetotransport enables us to establish the correlation between the nonlinear magnetoresistance and the spin textures in the Rashba system. Our findings offer significant fundamental insight into the physics underlying the nonreciprocity and may pave a route for future rectification devices. Most work on nonreciprocal transport is limited to cryogenic temperatures due to the low Rashba spin splitting energy. Here, the authors report a nonreciprocal charge transport behavior up to room temperature in semiconductor a GeTe with coexisting the surface and bulk Rashba states.
author_names: Yunguo Li

Yang Li

Peng Li

Bin Fang

Xu Yang

Yan Wen

Dongxing Zheng

Chenhui Zhang

Xin He

Aurelien Manchon

Zhaohua Cheng

Xi-xiang Zhang
title: Nonreciprocal charge transport up to room temperature in bulk Rashba semiconductor a GeTe
venue: Nature communications
year: 2021

abstract: Nonreciprocal charge transport phenomena are studied theoretically for two dimensional noncentrosymmetric superconductors under an external magnetic field $B$ Rashba superconductors, surface superconductivity on the surface of three dimensional topological insulators, and transition metal dichalcogenides such as \mathrm{MoS}}_{2} are representative systems, and the current voltage $I\ensuremath{ }V$ characteristics, i.e. $V=V(I) for each of them is analyzed. $V(I) can be expanded with respect to the current $I$ as $V(I)\ensuremath{\sum}}_{j=1,\ensuremath{\infty}{a}_{j}(B,T){I}{j} and the (B,T) dependence of {a}_{j} depends on the mechanism of the charge transport. Our analysis is based on the time dependent Ginzburg Landau theory, which contains up to third order terms in the momentum of the order parameter. Above the mean field superconducting transition temperature {T}_{0} the fluctuation of the superconducting order parameter gives the additional conductivity, i.e. paraconductivity. With the extension of paraconductivity to the nonlinear response, we obtain the nonreciprocal charge transport. On the other hand, below {T}_{0} the vortices determine the Kosterlitz Thouless transition and also the resistivity. The nonreciprocal resistivity is analyzed from the dynamics of vortices in this temperature region. Based on these results, we propose the experiments to identify the mechanism of the nonreciprocal transport with the realistic estimates for the order of magnitude of the coefficients {a}_{j}(B,T) for each case.
author_names: Shintaro Hoshino

Ryohei Wakatsuki

Keita Hamamoto

Naoto Nagaosa
title: Nonreciprocal charge transport in two dimensional noncentrosymmetric superconductors
year: 2018

abstract: The proximity of a transition metal dichalcogenide (TMD) to graphene imprints a rich spin texture in graphene and complements its high quality charge/spin transport by inducing spin orbit coupling (SOC) Rashba and valley Zeeman SOCs are the origin of charge to spin conversion mechanisms such as the Rashba Edelstein effect (REE) and spin Hall effect (SHE) In this work, we experimentally demonstrate for the first time charge to spin conversion due to the REE in a monolayer WS2 graphene van der Waals heterostructure. We measure the current induced spin polarization up to room temperature and control it by a gate electric field. Our observation of the REE and the inverse of the effect (IREE) is accompanied by the SHE, which we discriminate by symmetry resolved spin precession under oblique magnetic fields. These measurements also allow for the quantification of the efficiencies of charge to spin conversion by each of the two effects. These findings are a clear indication of induced Rashba and valley Zeeman SOC in graphene that lead to the generation of spin accumulation and spin current without using ferromagnetic electrodes. These realizations have considerable significance for spintronic applications, providing accessible routes toward all electrical spin generation and manipulation in two dimensional materials.
author_names: Talieh S Ghiasi

Alexey A Kaverzin

Patrick J Blah

Bart van Wees
title: Charge to Spin Conversion by the Rashba Edelstein Effect in Two Dimensional van der Waals Heterostructures up to Room Temperature
venue: Nano letters
year: 2019

abstract: Abstract The quantum interference effect in the charge transport through single phenyl molecules received intensive interests from theory but remained as an experimental challenge. In this paper, we investigated the charge transport through single molecule benzene dithiol (BDT) junction with different connectivities using mechanically controllable break junction (MCBJ) technique. By further improving the mechanical stability and the electronic measuring component of the MCBJ set up, we obtained the conductance histograms of BDT molecules (BDTs) from the statistical analysis of conductance distance traces without data selection. By tuning the connectivity, the conductance of BDTs is determined to be 10 1.2 G0, 10 2.2 G0 and 10 1.0 G0 for para, meta, and ortho connectivity, following the trend that ortho BDT para BDT meta BDT. Furthermore, the displacements of the junctions followed the trend that para meta ortho, suggesting the charge transport through the molecules via the gold thiol bond. The different trends between conductance and displacement for different connectivities suggests the presence of destructive quantum interference effect on meta BDT, which provides the experimental evidence for the quantum interference effect through single phenyl molecular junctions.
author_names: Guogang Yang

Hao Wu

Junying Wei

Jueting Zheng

Zhao-Bin Chen

Junyang Liu

Jia Shi

Yang Yang

Wenjing Hong
title: Quantum interference effect in the charge transport through single molecule benzene dithiol junction at room temperature: An experimental investigation
year: 2018

abstract: The proximity of a transition metal dichalcogenide (TMD) to graphene imprints a rich spin texture in graphene and complements its high quality charge/spin transport by inducing spin orbit coupling (SOC) Rashba and valley Zeeman SOCs are the origin of charge to spin conversion mechanisms such as Rashba Edelstein effect (REE) and spin Hall effect (SHE) In this work, we experimentally demonstrate for the first time charge to spin conversion due to the REE in a monolayer WS2 graphene van der Waals heterostructure. We measure the current induced spin polarization up to room temperature and control it by a gate electric field. Our observation of the REE and inverse of the effect (IREE) is accompanied by the SHE which we discriminate by symmetry resolved spin precession under oblique magnetic fields. These measurements also allow for quantification of the efficiencies of charge to spin conversion by each of the two effects. These findings are a clear indication of induced Rashba and valley Zeeman SOC in graphene that lead to generation of spin accumulation and spin current without using ferromagnetic electrodes. These realizations have considerable significance for spintronic applications, providing accessible routes towards all electrical spin generation and manipulation in two dimensional materials.
author_names: Talieh S Ghiasi

Alexey A Kaverzin

Patrick J Blah

Bart Jan van Wees
title: Charge to Spin Conversion by the Rashba Edelstein Effect in 2D van der Waals Heterostructures up to Room Temperature
year: 2019

abstract: Understanding charge transport in DNA molecules is a long standing problem of fundamental importance across disciplines 1 2 It is also of great technological interest due to DNA's ability to form versatile and complex programmable structures. Charge transport in DNA based junctions has been reported using a wide variety of set ups 2 4 but experiments so far have yielded seemingly contradictory results that range from insulating 5 8 or semiconducting 9 10 to metallic like behaviour 11 As a result, the intrinsic charge transport mechanism in molecular junction set ups is not well understood, which is mainly due to the lack of techniques to form reproducible and stable contacts with individual long DNA molecules. Here we report charge transport measurements through single 30 nm long double stranded DNA (dsDNA) molecules with an experimental set up that enables us to address individual molecules repeatedly and to measure the current voltage characteristics from 5 K up to room temperature. Strikingly, we observed very high currents of tens of nanoamperes, which flowed through both homogeneous and non homogeneous base pair sequences. The currents are fairly temperature independent in the range 5 60 K and show a power law decrease with temperature above 60 K, which is reminiscent of charge transport in organic crystals. Moreover, we show that the presence of even a single discontinuity 'nick' in both strands that compose the dsDNA leads to complete suppression of the current, which suggests that the backbones mediate the long distance conduction in dsDNA, contrary to the common wisdom in DNA electronics 2 4 Measurements of electrical conductance in double stranded DNA suggest that the backbones mediate the long distance conduction in dsDNA, contrary to the common wisdom in DNA electronics.
author_names: Roman Zhuravel

Haichao Huang

Georgia Polycarpou

Savvas Polydorides

Phani Motamarri

Liat Katrivas

Dvir Rotem

Joseph Sperling

Linda A Zotti

Alexander Kotlyar

Juan Carlos Cuevas

Vikram Gavini

Spiros S Skourtis

Danny Porath
title: Backbone charge transport in double stranded DNA
venue: Nature Nanotechnology
year: 2020

abstract: Hybrid nanocomposites (HNCs) of polypyrrole (PPy) and CuS were synthesized by an in situ chemical polymerization method. The HNCs were prepared by varying the CuS nanoparticles weight percentage (10 40% in PPy matrix. The XRD and FESEM characterization indicated the uniform distribution of CuS nanoparticles in PPy matrix. The XRD pattern revealed the presence of hexagonal CuS peaks overlapped with amorphous PPy pattern. Williamson Hall method was employed to estimate intrinsic strain in HNCs. FTIR spectrum revealed the shifting of 1025 cm 1 peak toward higher wavenumber, indicating insertion of CuS nanoparticles in PPy. The room temperature electrical conductivity of PPy is found to be increased from 1.15 x 10 1 to 3.70 S/cm as the content of CuS nanoparticles increases up to 40 wt% in HNCs. To explore the charge transport mechanism in HNCs,the conductivity was measured in the temperature range of 300 15 K. The measured conductivity data was analyzed with the help of Arrhenius model and 3d Mott's variable range hopping (VRH) model in the temperature range of 35 300 K. The approximate values of Mott's parameters at 300 K such as the density of states at Fermi level, average hopping distance and average hopping energy of HNCs were estimated as 4x10 24 cm 3 eV 1 1.7 A and 10 meV respectively.
author_names: Narinder Singh

Manish Taunk
title: In Situ Chemical Synthesis, Microstructural, Morphological and Charge Transport Studies of Polypyrrole CuS Hybrid Nanocomposites
venue: Journal of Inorganic and Organometallic Polymers and Materials
year: 2020

abstract: Poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is an important opto electronic material, and its room temperature electrical conductivity can be prominently enhanced by chemical treatment; it is technologically significant to investigate its temperature and magnetic field dependent charge transport characteristics. Here, we analyzed the low temperature charge transport properties of pristine and acid treated PEDOT:PSS thin films by studying the variation in resistance as a function of temperature and magnetic field (T 300 to 4.2 K, H up to 5 T) The acid treated sample exhibited much improved charge transport behavior at low T, with a resistivity ratio [r(4.2 K)/r(300 K) of ~5.7 x 102, which is three orders of magnitude smaller than that of the pristine sample. Nevertheless, both pristine and acid treated samples followed hopping conduction, obeying R T exp T 1 2 and R T exp T 1 3, respectively, in the low T regime. Furthermore, positive magnetoresistance of ~16% (at 4.2 K and 5 T) was displayed by acid treated samples that could be due to the wave function shrinkage phenomenon.
author_names: Meenu Sharma

Krishna Prasad Maity

Sonam Rani

V D Prasad

I Sameera

Ravi Bhatia
title: Temperature dependent charge transport of acid treated poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films
year: 2020

abstract: Abstract Sb2S3 thin film solar cells have recently gained attention due to their low cost, low toxicity, and simple fabrication. However, there is still plenty of room to improve their performance. It is known that efficient carrier transport is essential for high performance Sb2S3 solar cells, which, unfortunately, is difficult to characterize by conventional testing methods. Therefore, the carrier transport process in Sb2S3 solar cells was studied here using a theoretical simulation. The results show that high solar performances can be achieved with a wide parameter window for selecting the electron transport layer as well as the hole transport layer, viz. with a conduction band minimum of the electron transport layer 4.4 eV VBM 6.4 eV) Here the interfacial potential barrier become negligible and as a consequence electrons and holes cross at ease, which guarantee the good device performance. Indeed, a Sb2S3 solar cell with a high power conversion efficiency (PCE) can be obtained by ensuring that the carrier transport and collection are unimpeded in the device, i.e. the Sb2S3 based single junction solar cells shows high efficiency of 19.53% Furthermore, we found that optimized Sb2S3 solar cells are particularly suitable for use as the top cell of tandem structure solar cells. Thus, a Sb2S3/Sb2Se3 double junction solar cell structure was proposed. With a 0.5 mm thick Sb2S3 absorber, double junction solar cells could achieve a theoretical efficiency as high as 26.64% Our results based on the rotational design of bandgap alignment provide a general guide rule for selecting the optimal electron transport layer as well as the hole transport layer to boost the power conversion efficiency for Sb2S3 solar cells up to its theoretical limit.
author_names: Yu Cao

Xinyun Zhu

Jiahao Jiang

Chaoying Liu

Jing Zhou

Jian Ni

Jianjun Zhang

Jinbo Pang
title: Rotational design of charge carrier transport layers for optimal antimony trisulfide solar cells and its integration in tandem devices
year: 2020

abstract: Fullerene based materials are widely used as acceptor and electron transport layer materials in organic and planar perovskite solar cells. Modeling of electronic properties such as band alignment and charge transport for these applications is typically done using optimized geometries. Here, we estimate the effects of nuclear motions on band structure and electron and hole transport in two prototypical fullerenes, C60 and C70. We model the dynamics in solid fullerenes using Density Functional Tight Binding and we use the Density Functional Theory based Projection of Monomer Orbitals on Dimer Orbitals (DIPRO) approach to estimate effects on charge transfer integral in the Marcus approximation. We show that room temperature molecular dynamics cause a shift and spread of frontier orbital energies on the order of 0.1 eV which leads to an increase by more than a factor of two in the Marcus exponent, and can cause a decrease by up to orders of magnitude in the overlap integral, leading in most cases to an overall decrease in the charge transport rate.
author_names: Saeid Arabnejad

Amrita Pal

Koichi Yamashita

Sergei Manzhos
title: Effect of Nuclear Motion on Charge Transport in Fullerenes: A Combined Density Functional Tight Binding Density Functional Theory Investigation
venue: Front. Energy Res.
year: 2019