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151. Quantum Hall effect based on Weyl orbits in Cd3As2

Author

Zhang, Cheng, primary, Zhang, Yi, additional, Yuan, Xiang, additional, Lu, Shiheng, additional, Zhang, Jinglei, additional, Narayan, Awadhesh, additional, Liu, Yanwen, additional, Zhang, Huiqin, additional, Ni, Zhuoliang, additional, Liu, Ran, additional, Choi, Eun Sang, additional, Suslov, Alexey, additional, Sanvito, Stefano, additional, Pi, Li, additional, Lu, Hai-Zhou, additional, Potter, Andrew C., additional, and Xiu, Faxian, additional

Published
2018
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152. Strain and ferroelectric soft-mode induced superconductivity in strontium titanate

Author

Dunnett, K., Narayan, Awadhesh, Spaldin, N. A., Balatsky, Alexander, Dunnett, K., Narayan, Awadhesh, Spaldin, N. A., and Balatsky, Alexander

Abstract

We investigate the effects of strain on superconductivity with particular reference to SrTiO3. Assuming that a ferroelectric mode that softens under tensile strain is responsible for the coupling, an increase in the critical temperature and range of carrier densities for superconductivity is predicted, while the peak of the superconducting dome shifts towards lower carrier densities. Using a Ginzburg-Landau approach in 2D, we find a linear dependence of the critical temperature on strain: if the couplings between the order parameter and strains in different directions differ while their sum is fixed, different behaviors under uniaxial and biaxial strain can be understood., QC 20180508

Published
2018
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153. Edge superconductivity in multilayer WTe2 Josephson junction.

Author

Huang, Ce, Narayan, Awadhesh, Zhang, Enze, Xie, Xiaoyi, Ai, Linfeng, Liu, Shanshan, Yi, Changjiang, Shi, Youguo, Sanvito, Stefano, and Xiu, Faxian

Subjects
*JOSEPHSON effect, *SUPERCONDUCTIVITY, *CONDENSED matter physics, *JOSEPHSON junctions, *BAND gaps, *QUANTUM interference, *QUANTUM measurement
Abstract

WTe2, as a type-II Weyl semimetal, has 2D Fermi arcs on the (001) surface in the bulk and 1D helical edge states in its monolayer. These features have recently attracted wide attention in condensed matter physics. However, in the intermediate regime between the bulk and monolayer, the edge states have not been resolved owing to its closed band gap which makes the bulk states dominant. Here, we report the signatures of the edge superconductivity by superconducting quantum interference measurements in multilayer WTe2 Josephson junctions and we directly map the localized supercurrent. In thick WTe2 (⁠|$\sim 60{\rm{\ nm}})$|⁠ , the supercurrent is uniformly distributed by bulk states with symmetric Josephson effect (⁠|$| {I_c^ + (B)} | {=} | {I_c^ - (B)} |\ $|⁠). In thin WTe2 (10 nm), however, the supercurrent becomes confined to the edge and its width reaches up to |$1.4{\rm{\ \mu m\ }}$| and exhibits non-symmetric behavior |$| {I_c^ + (B)} | \ne | {I_c^ - (B)} |$|⁠. The ability to tune the edge domination by changing thickness and the edge superconductivity establishes WTe2 as a promising topological system with exotic quantum phases and a rich physics. [ABSTRACT FROM AUTHOR]

Published
2020
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155. Inducing Strong Superconductivity in WTe2 by a Proximity Effect

Author

Huang, Ce, primary, Narayan, Awadhesh, additional, Zhang, Enze, additional, Liu, Yanwen, additional, Yan, Xiao, additional, Wang, Jiaxiang, additional, Zhang, Cheng, additional, Wang, Weiyi, additional, Zhou, Tong, additional, Yi, Changjiang, additional, Liu, Shanshan, additional, Ling, Jiwei, additional, Zhang, Huiqin, additional, Liu, Ran, additional, Sankar, Raman, additional, Chou, Fangcheng, additional, Wang, Yihua, additional, Shi, Youguo, additional, Law, Kam Tuen, additional, Sanvito, Stefano, additional, Zhou, Peng, additional, Han, Zheng, additional, and Xiu, Faxian, additional

Published
2018
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158. Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide

Author

Dankert, Andre, Pashaei, Parham, Kamalakar, M. Venkata, Gaur, Anand P. S., Sahoo, Satyaprakash, Rungger, Ivan, Narayan, Awadhesh, Dolui, Kapildeb, Hoque, Md. Anamul, Patel, Ram Shanker, de Jong, Michel P., Katiyar, Ram S., Sanvito, Stefano, Dash, Saroj P., Dankert, Andre, Pashaei, Parham, Kamalakar, M. Venkata, Gaur, Anand P. S., Sahoo, Satyaprakash, Rungger, Ivan, Narayan, Awadhesh, Dolui, Kapildeb, Hoque, Md. Anamul, Patel, Ram Shanker, de Jong, Michel P., Katiyar, Ram S., Sanvito, Stefano, and Dash, Saroj P.

Abstract

The two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS2 (similar to 7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.

Published
2017
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160. Evolution of Weyl orbit and quantum Hall effect in Dirac semimetal Cd3As2

Author

Zhang, Cheng, primary, Narayan, Awadhesh, additional, Lu, Shiheng, additional, Zhang, Jinglei, additional, Zhang, Huiqin, additional, Ni, Zhuoliang, additional, Yuan, Xiang, additional, Liu, Yanwen, additional, Park, Ju-Hyun, additional, Zhang, Enze, additional, Wang, Weiyi, additional, Liu, Shanshan, additional, Cheng, Long, additional, Pi, Li, additional, Sheng, Zhigao, additional, Sanvito, Stefano, additional, and Xiu, Faxian, additional

Published
2017
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161. Evidence for pressure-induced node-pair annihilation in Cd3As2

Author

Zhang, Cheng, primary, Sun, Jianping, additional, Liu, Fengliang, additional, Narayan, Awadhesh, additional, Li, Nana, additional, Yuan, Xiang, additional, Liu, Yanwen, additional, Dai, Jianhong, additional, Long, Youwen, additional, Uwatoko, Yoshiya, additional, Shen, Jian, additional, Sanvito, Stefano, additional, Yang, Wenge, additional, Cheng, Jinguang, additional, and Xiu, Faxian, additional

Published
2017
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163. Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide

Author

Dankert, André, primary, Pashaei, Parham, additional, Kamalakar, M. Venkata, additional, Gaur, Anand P. S., additional, Sahoo, Satyaprakash, additional, Rungger, Ivan, additional, Narayan, Awadhesh, additional, Dolui, Kapildeb, additional, Hoque, Md. Anamul, additional, Patel, Ram Shanker, additional, de Jong, Michel P., additional, Katiyar, Ram S., additional, Sanvito, Stefano, additional, and Dash, Saroj P., additional

Published
2017
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166. Quantum Hall effect based on Weyl orbits in Cd3As2.

Author

Zhang, Cheng, Zhang, Yi, Yuan, Xiang, Lu, Shiheng, Zhang, Jinglei, Narayan, Awadhesh, Liu, Yanwen, Zhang, Huiqin, Ni, Zhuoliang, Liu, Ran, Choi, Eun Sang, Suslov, Alexey, Sanvito, Stefano, Pi, Li, Lu, Hai-Zhou, Potter, Andrew C., and Xiu, Faxian

Abstract

Discovered decades ago, the quantum Hall effect remains one of the most studied phenomena in condensed matter physics and is relevant for research areas such as topological phases, strong electron correlations and quantum computing1-5. The quantized electron transport that is characteristic of the quantum Hall effect typically originates from chiral edge states—ballistic conducting channels that emerge when two-dimensional electron systems are subjected to large magnetic fields2. However, whether the quantum Hall effect can be extended to higher dimensions without simply stacking two-dimensional systems is unknown. Here we report evidence of a new type of quantum Hall effect, based on Weyl orbits in nanostructures of the three-dimensional topological semimetal Cd3As2. The Weyl orbits consist of Fermi arcs (open arc-like surface states) on opposite surfaces of the sample connected by one-dimensional chiral Landau levels along the magnetic field through the bulk6,7. This transport through the bulk results in an additional contribution (compared to stacked two-dimensional systems and which depends on the sample thickness) to the quantum phase of the Weyl orbit. Consequently, chiral states can emerge even in the bulk. To measure these quantum phase shifts and search for the associated chiral modes in the bulk, we conduct transport experiments using wedge-shaped Cd3As2 nanostructures with variable thickness. We find that the quantum Hall transport is strongly modulated by the sample thickness. The dependence of the Landau levels on the magnitude and direction of the magnetic field and on the sample thickness agrees with theoretical predictions based on the modified Lifshitz-Onsager relation for the Weyl orbits. Nanostructures of topological semimetals thus provide a way of exploring quantum Hall physics in three-dimensional materials with enhanced tunability. Quantized conductivity is observed along a Weyl orbit in wedge-shaped samples of the topological semimetal Cd3As2, providing evidence of the quantum Hall effect in three dimensions. [ABSTRACT FROM AUTHOR]

Published
2019
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167. Charge Density Wave and Narrow Energy Gap at Room Temperature in 2D Pb3–xSb1+xS4Te2−δwith Square Te Sheets

Author

Chen, Haijie, Malliakas, Christos D., Narayan, Awadhesh, Fang, Lei, Chung, Duck Young, Wagner, Lucas K., Kwok, Wai-Kwong, and Kanatzidis, Mercouri G.

Abstract

We report a new two-dimensional compound, Pb3–xSb1+xS4Te2−δ, that has a charge density wave (CDW) at room temperature. The CDW is incommensurate with q-vector of 0.248(6)a* + 0.246(8)b* + 0.387(9)c* for x= 0.29(2) and δ = 0.37(3) due to positional and occupational long-range ordering of Te atoms in the sheets. The modulated structure was refined from the single-crystal X-ray diffraction data with a superspace group P1̅(αβγ)0 using (3 + 1)-dimensional crystallography. The resistivity increases with decreasing temperature, suggesting semiconducting behavior. The transition temperature (TCDW) of the CDW is ∼345 K, above which the Te square sheets become disordered with no q-vector. First-principles density functional theory calculations on the undistorted structure and an approximate commensurate supercell reveal that the gap is due to the structure modulation.

Published
2024
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168. Chirality-Tunable Nonlinear Hall Effect

Author

Joseph, Nesta Benno, Bandyopadhyay, Arka, and Narayan, Awadhesh

Abstract

The nonlinear generalization of the Hall effect has recently gained much attention, with a rapidly growing list of noncentrosymmetric materials that display higher-order Hall responses under time-reversal invariant conditions. The intrinsic second-order Hall response arises due to the first-order moment of Berry curvature─termed Berry curvature dipole─which requires broken inversion and low crystal symmetries. Chiral materials are characterized by their lack of improper symmetries such as inversion, mirror plane, and roto-inversion. Owing to this absence of symmetries, in this work, we propose chiral systems as ideal platforms to study the Berry curvature dipole-induced nonlinear Hall effects. We use state-of-the-art first-principles computations, in conjunction with symmetry analyses, to explore a variety of chiral material classes─metallic NbSi2, semiconducting elemental Te, insulating HgS, and topological multifold semimetal CoSi. We present the emergence and tunability of the Berry curvature dipole in these chiral materials. In particular, we demonstrate that the two enantiomeric pairs exhibit an exactly opposite sign of the Berry curvature dipole. We complement our ab initiofindings with a general tight-binding minimal model and give estimates for nonlinear Hall voltages, which are experimentally accessible. Our predictions put forward chiral materials as an emerging class of materials to realize nonlinear Hall phenomena and highlight an as-yet-unexplored aspect of these systems.

Published
2024
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169. Zeeman splitting and dynamical mass generation in Dirac semimetal ZrTe5

Author

Liu, Yanwen, Yuan, Xiang, Zhang, Cheng, Jin, Zhao, Narayan, Awadhesh, Luo, Chen, Chen, Zhigang, Yang, Lei, Zou, Jin, Wu, Xing, Sanvito, Stefano, Xia, Zhengcai, Li, Liang, Wang, Zhong, Xiu, Faxian, Liu, Yanwen, Yuan, Xiang, Zhang, Cheng, Jin, Zhao, Narayan, Awadhesh, Luo, Chen, Chen, Zhigang, Yang, Lei, Zou, Jin, Wu, Xing, Sanvito, Stefano, Xia, Zhengcai, Li, Liang, Wang, Zhong, and Xiu, Faxian

Abstract

Dirac semimetals have attracted extensive attentions in recent years. It has been theoretically suggested that many-body interactions may drive exotic phase transitions, spontaneously generating a Dirac mass for the nominally massless Dirac electrons. So far, signature of interaction-driven transition has been lacking. In this work, we report high-magnetic-field transport measurements of the Dirac semimetal candidate ZrTe5. Owing to the large g factor in ZrTe5, the Zeeman splitting can be observed at magnetic field as low as 3 T. Most prominently, high pulsed magnetic field up to 60 T drives the system into the ultra-quantum limit, where we observe abrupt changes in the magnetoresistance, indicating field-induced phase transitions. This is interpreted as an interaction-induced spontaneous mass generation of the Dirac fermions, which bears resemblance to the dynamical mass generation of nucleons in high-energy physics. Our work establishes Dirac semimetals as ideal platforms for investigating emerging correlation effects in topological matters.

Published
2016

170. Observation of quasi-two-dimensional Dirac fermions in ZrTe5

Author

Yuan, Xiang, primary, Zhang, Cheng, additional, Liu, Yanwen, additional, Narayan, Awadhesh, additional, Song, Chaoyu, additional, Shen, Shoudong, additional, Sui, Xing, additional, Xu, Jie, additional, Yu, Haochi, additional, An, Zhenghua, additional, Zhao, Jun, additional, Sanvito, Stefano, additional, Yan, Hugen, additional, and Xiu, Faxian, additional

Published
2016
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172. Zeeman splitting and dynamical mass generation in Dirac semimetal ZrTe5

Author

Liu, Yanwen, primary, Yuan, Xiang, additional, Zhang, Cheng, additional, Jin, Zhao, additional, Narayan, Awadhesh, additional, Luo, Chen, additional, Chen, Zhigang, additional, Yang, Lei, additional, Zou, Jin, additional, Wu, Xing, additional, Sanvito, Stefano, additional, Xia, Zhengcai, additional, Li, Liang, additional, Wang, Zhong, additional, and Xiu, Faxian, additional

Published
2016
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176. Gate-tunable quantum oscillations in ambipolar Cd3As2 thin films

Author

Liu, Yanwen, primary, Zhang, Cheng, additional, Yuan, Xiang, additional, Lei, Tang, additional, Wang, Chao, additional, Di Sante, Domenico, additional, Narayan, Awadhesh, additional, He, Liang, additional, Picozzi, Silvia, additional, Sanvito, Stefano, additional, Che, Renchao, additional, and Xiu, Faxian, additional

Published
2015
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177. Controlling the Spin Texture of Topological Insulators by Rational Design of Organic Molecules

Author

Jakobs, Sebastian, primary, Narayan, Awadhesh, additional, Stadtmüller, Benjamin, additional, Droghetti, Andrea, additional, Rungger, Ivan, additional, Hor, Yew S., additional, Klyatskaya, Svetlana, additional, Jungkenn, Dominik, additional, Stöckl, Johannes, additional, Laux, Martin, additional, Monti, Oliver L. A., additional, Aeschlimann, Martin, additional, Cava, Robert J., additional, Ruben, Mario, additional, Mathias, Stefan, additional, Sanvito, Stefano, additional, and Cinchetti, Mirko, additional

Published
2015
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178. Spin-Valve Effect in NiFe/MoS2/NiFe Junctions

Author

Wang, Weiyi, primary, Narayan, Awadhesh, additional, Tang, Lei, additional, Dolui, Kapildeb, additional, Liu, Yanwen, additional, Yuan, Xiang, additional, Jin, Yibo, additional, Wu, Yizheng, additional, Rungger, Ivan, additional, Sanvito, Stefano, additional, and Xiu, Faxian, additional

Published
2015
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183. Evolution of Weyl orbit and quantum Hall effect in Dirac semimetal Cd3As2.

Author

Cheng Zhang, Narayan, Awadhesh, Shiheng Lu, Jinglei Zhang, Huiqin Zhang, Zhuoliang Ni, Xiang Yuan, Yanwen Liu, Ju-Hyun Park, Enze Zhang, Weiyi Wang, Shanshan Liu, Long Cheng, Li Pi, Zhigao Sheng, Sanvito, Stefano, and Faxian Xiu

Subjects
LANDAU levels, QUANTUM states, FREQUENCIES of oscillating systems, ORBITS (Astronomy), SURFACE states, QUANTUM Hall effect, CARRIER density
Abstract

Owing to the coupling between open Fermi arcs on opposite surfaces, topological Dirac semimetals exhibit a new type of cyclotron orbit in the surface states known as Weyl orbit. Here, by lowering the carrier density in Cd3As2 nanoplates, we observe a crossover from multiple-frequency to single-frequency Shubnikov-de Haas (SdH) oscillations when subjected to out-of-plane magnetic field, indicating the dominant role of surface transport. With the increase of magnetic field, the SdH oscillations further develop into quantum Hall state with non-vanishing longitudinal resistance. By tracking the oscillation frequency and Hall plateau, we observe a Zeeman-related splitting and extract the Landau level index as well as sub-band number. Different from conventional two-dimensional systems, this unique quantum Hall effect may be related to the quantized version of Weyl orbits. Our results call for further investigations into the exotic quantum Hall states in the low-dimensional structure of topological semimetals. [ABSTRACT FROM AUTHOR]

Published
2017
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188. Inducing Strong Superconductivity in WTe2by a Proximity Effect

Author

Huang, Ce, Narayan, Awadhesh, Zhang, Enze, Liu, Yanwen, Yan, Xiao, Wang, Jiaxiang, Zhang, Cheng, Wang, Weiyi, Zhou, Tong, Yi, Changjiang, Liu, Shanshan, Ling, Jiwei, Zhang, Huiqin, Liu, Ran, Sankar, Raman, Chou, Fangcheng, Wang, Yihua, Shi, Youguo, Law, Kam Tuen, Sanvito, Stefano, Zhou, Peng, Han, Zheng, and Xiu, Faxian

Abstract

The search for proximity-induced superconductivity in topological materials has generated widespread interest in the condensed matter physics community. The superconducting states inheriting nontrivial topology at interfaces are expected to exhibit exotic phenomena such as topological superconductivity and Majorana zero modes, which hold promise for applications in quantum computation. However, a practical realization of such hybrid structures based on topological semimetals and superconductors has hitherto been limited. Here, we report the strong proximity-induced superconductivity in type-II Weyl semimetal WTe2, in a van der Waals hybrid structure obtained by mechanically transferring NbSe2onto various thicknesses of WTe2. When the WTe2thickness (tWTe2) reaches 21 nm, the superconducting transition occurs around the critical temperature (Tc) of NbSe2with a gap amplitude (Δp) of 0.38 meV and an unexpected ultralong proximity length (lp) up to 7 μm. With the thicker 42 nm WTe2layer, however, the proximity effect yields Tc≈ 1.2 K, Δp= 0.07 meV, and a short lpof less than 1 μm. Our theoretical calculations, based on the Bogoliubov–de Gennes equations in the clean limit, predict that the induced superconducting gap is a sizable fraction of the NbSe2superconducting one when tWTe2is less than 30 nm and then decreases quickly as tWTe2increases. This agrees qualitatively well with the experiments. Such observations form a basis in the search for superconducting phases in topological semimetals.

Published
2018
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193. Semiconducting Ba3Sn3Sb4and Metallic Ba7–xSn11Sb15–y(x= 0.4, y= 0.6) Zintl Phases

Author

Chen, Haijie, Narayan, Awadhesh, Stoumpos, Constantinos C., Zhao, Jing, Han, Fei, Chung, Duck Young, Wagner, Lucas K., Kwok, Wai-Kwong, and Kanatzidis, Mercouri G.

Abstract

We report the discovery of two ternary Zintl phases Ba3Sn3Sb4and Ba7–xSn11Sb15–y(x= 0.4, y= 0.6). Ba3Sn3Sb4adopts the monoclinic space group P21/cwith a= 14.669(3) Å, b= 6.9649(14) Å, c= 13.629(3) Å, and β = 104.98(3)°. It features a unique corrugated two-dimensional (2D) structure consisting of [Sn3Sb4]6–layers extending along the ab-plane with Ba2+atoms sandwiched between them. The nonstoichiometric Ba6.6Sn11Sb14.4has a complex one-dimensional (1D) structure adopting the orthorhombic space group Pnma, with unit cell parameters a= 37.964(8) Å, b= 4.4090(9) Å, and c= 24.682(5) Å. It consists of large double Sn–Sb ribbons separated by Ba2+atoms. Ba3Sn3Sb4is an n-type semiconductor which has a narrow energy gap of ∼0.18 eV and a room temperature carrier concentration of ∼4.2 × 1018cm–3. Ba6.6Sn11Sb14.4is determined to be a metal with electrons being the dominant carriers.

Published
2017
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194. Efficient spin injection and giant magnetoresistance in Fe/MoS2/Fe junctions.

Author

Dolui, Kapildeb, Narayan, Awadhesh, Rungger, Ivan, and Sanvito, Stefano

Subjects
*SPINTRONICS, *MICROELECTRONICS, *QUANTUM wells, *IRON compounds spectra, *GIANT magnetoimpedance effect
Abstract

We demonstrate giant magnetoresistance in Fe/MoS2/Fe junctions by means of ab initio transport calculations. We show that junctions incorporating either a monolayer or a bilayer of MoS2 are metallic and that Fe acts as an efficient spin injector into MoS2 with an efficiency of about 45%. This is the result of the strong coupling between the Fe and S atoms at the interface. For junctions of greater thickness, a maximum magnetoresistance of ∼300% is obtained, which remains robust with the applied bias as long as transport is in the tunneling limit. A general recipe for improving the magnetoresistance in spin valves incorporating layered transition metal dichalcogenides is proposed. [ABSTRACT FROM AUTHOR]

Published
2014
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195. Tuning 2D magnetism in Fe3+XGeTe2films by element doping

Author

Liu, Shanshan, Li, Zihan, Yang, Ke, Zhang, Enze, Narayan, Awadhesh, Zhang, Xiaoqian, Zhu, Jiayi, Liu, Wenqing, Liao, Zhiming, Kudo, Masaki, Toriyama, Takaaki, Yang, Yunkun, Li, Qiang, Ai, Linfeng, Huang, Ce, Sun, Jiabao, Guo, Xiaojiao, Bao, Wenzhong, Deng, Qingsong, Chen, Yanhui, Yin, Lifeng, Shen, Jian, Han, Xiaodong, Matsumura, Syo, Zou, Jin, Xu, Yongbing, Xu, Xiaodong, Wu, Hua, and Xiu, Faxian

Abstract

Two-dimensional (2D) ferromagnetic materials have been discovered with tunable magnetism and orbital-driven nodal-line features. Controlling the 2D magnetism in exfoliated nanoflakes via electric/magnetic fields enables a boosted Curie temperature (TC) or phase transitions. One of the challenges, however, is the realization of high TC2D magnets that are tunable, robust and suitable for large scale fabrication. Here, we report molecular-beam epitaxy growth of wafer-scale Fe3+XGeTe2films with TCabove room temperature. By controlling the Fe composition in Fe3+XGeTe2, a continuously modulated TCin a broad range of 185–320 K has been achieved. This widely tunable TCis attributed to the doped interlayer Fe that provides a 40% enhancement around the optimal composition X = 2. We further fabricated magnetic tunneling junction device arrays that exhibit clear tunneling signals. Our results show an effective and reliable approach, i.e. element doping, to producing robust and tunable ferromagnetism beyond room temperature in a large-scale 2D Fe3+XGeTe2fashion.We report the tunable 2D ferromagnetism above-room-temperature in wafer-scale Fe3+XGeTe2films and demonstrate magnetic tunneling junction arrays using Fe3+XGeTe2films.

Published
2022
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196. Hidden spin polarization in nonmagnetic centrosymmetric BaNiS2 crystal: Signatures from first principles.

Author

Sławińska, Jagoda, Narayan, Awadhesh, and Picozzi, Silvia

Subjects
*SPIN polarization, *BARIUM compounds, *RASHBA effect
Abstract

The recent discovery of hidden spin polarization emerging in bulk electronic states of specific nonmagnetic crystals is a fascinating phenomenon, though hardly explored yet. Here, we study from a theoretical perspective nonmagnetic BaNiS2, recently suggested to exhibit a giant Rashba-like spin-orbit splitting of the bulk bands, despite the absence of heavy elements. We employ density functional theory and Green's functions calculations to reveal the exact spin textures of both bulk and surface. We predict unambiguous signatures of spin-polarized electronic states at the surface, which reflect the bulk Rashba splitting and which could be experimentally measured with sufficient resolution: this would constitute a clear report of a bulk-Rashba-induced spin splitting at the surface of centrosymmetric crystals. [ABSTRACT FROM AUTHOR]

Published
2016
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197. From complex magnetism ordering to simple ferromagnetism in two-dimensional LaCrSb3 by hole doping.

Author

Haijie Chen, Narayan, Awadhesh, Lei Fang, Calta, Nicholas P., Fengyuan Shi, Chung, Duck Young, Wagner, Lucas K., Wai-Kwong Kwok, and Kanatzidis, Mercouri G.

Subjects
*FERROMAGNETISM, *LANTHANUM compounds, *DOPING agents (Chemistry), *SUPERCONDUCTIVITY, *ANISOTROPY, *DENSITY functional theory
Abstract

Competing orders widely exist in many material systems, such as superconductivity, magnetism, and ferroelectricity; LaCrSb3 is a highly anisotropic magnetic material in which the spins are aligned ferromagnetically in one direction and canted antiferromagnetically in another in the Cr-Sb chains. Hole doping with Sr2+ and Ca2+ in the La site suppresses the antiferromagnetic correlations and transforms the anisotropic magnetic order into a ferromagnetic lattice in all directions. First-principles density functional theory calculations show that the canted magnetic order becomes energetically less favorable compared to the FM order upon hole doping. Doping in the La site is an effective approach to modulate the competing orders in LaCrSb3. [ABSTRACT FROM AUTHOR]

Published
2016
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199. Gate-tunable quantum oscillations in ambipolar Cd3As2thin films

Author

Liu, Yanwen, Zhang, Cheng, Yuan, Xiang, Lei, Tang, Wang, Chao, Di Sante, Domenico, Narayan, Awadhesh, He, Liang, Picozzi, Silvia, Sanvito, Stefano, Che, Renchao, and Xiu, Faxian

Abstract

Electrostatic doping in materials can lead to various exciting electronic properties, such as metal–insulator transition and superconductivity, by altering the Fermi level position or introducing exotic phases. Cd3As2, a three-dimensional (3D) analog of graphene with extraordinary carrier mobility, was predicted to be a 3D Dirac semimetal, a feature confirmed by recent experiments. However, most research so far has been focused on metallic bulk materials that are known to possess ultra-high mobility and giant magneto-resistance but limited carrier transport tunability. Here we report on the first observation of a gate-induced transition from band conduction to hopping conduction in single-crystalline Cd3As2thin films via electrostatic doping by solid electrolyte gating. The extreme charge doping enables the unexpected observation of p-type conductivity in a ∼50-nm-thick Cd3As2thin film grown by molecular beam epitaxy. More importantly, the gate-tunable Shubnikov–de Haas oscillations and the temperature-dependent resistance reveal a unique band structure and bandgap opening when the dimensionality of Cd3As2is reduced. This is also confirmed by our first-principle calculations. The present results offer new insights toward nanoelectronic and optoelectronic applications of Dirac semimetals in general and provide new routes in the search for the intriguing quantum spin Hall effect in low-dimension Dirac semimetals, an effect that is theoretically predicted but not yet experimentally realized.

Published
2015
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