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Monolayer control of spin-charge conversion in van der Waals heterostructures
Authors:
K. Abdukayumov,
O. Paull,
M. Mičica,
F. Ibrahim,
L. Vojáček,
A. Wright,
S. Massabeau,
F. Mazzola,
V. Polewczyk,
C. Jego,
R. Sharma,
C. Vergnaud,
A. Marty,
I. Gomes de Moraes,
A. Ouerghi,
H. Okuno,
A. Jana,
I. Kar,
J. Fuji,
I. Vobornik,
J. Li,
F. Bonell,
M. Chshiev,
M. Bibes,
J. -M. George
, et al. (3 additional authors not shown)
Abstract:
The diversity of 2D materials and their van der Waals (vdW) stacking presents a fertile ground for engineering novel multifunctional materials and quantum states of matter. This permits unique opportunities to tailor the electronic properties of vdW heterostructures by the insertion of only a single 2D material layer. However, such vdW materials engineering at the atomic scale has yet to be invest…
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The diversity of 2D materials and their van der Waals (vdW) stacking presents a fertile ground for engineering novel multifunctional materials and quantum states of matter. This permits unique opportunities to tailor the electronic properties of vdW heterostructures by the insertion of only a single 2D material layer. However, such vdW materials engineering at the atomic scale has yet to be investigated for spin-charge interconversion phenomena. Here, we report on the control of these effects at the monolayer level, where drastic increase in intensity and change in sign of THz spintronic emission are demonstrated by inserting a single layer of MoSe$_2$ between PtSe$_2$ and graphene in a fully epitaxial, large area stacked structure. By using a combination of spin and angle resolved photoemission and density functional theory to reveal the electronic and spin structures, we illustrate two different mechanisms relying on charge transfer and electronic hybridization for the formation of Rashba states, which are responsible for spin-charge conversion and hence the THz spintronic emission. These findings open new pathways to design, at the atomic scale, efficient THz spintronic emitters made of 2D materials and other spintronic devices based on spin-charge interconversion phenomena.
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Submitted 4 January, 2025;
originally announced January 2025.
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Comparative study of Kondo effect in Vanadium dichalcogenides VX$_2$ (X=Se & Te)
Authors:
Indrani Kar,
Susanta Ghosh,
Shuvankar Gupta,
Sudip Chakraborty,
S. Thirupathaiah
Abstract:
We report on the electrical transport, magnetotransport, and magnetic properties studies on the transition metal dichalcogenides VSe$_2$ and VTe$_2$ and draw a comprehensive comparison between them. We observe Kondo effect in both systems induced by the exchange interaction between localized moments and conduction electrons at low temperature, resulting into resistance upturn at 6 K for VSe$_2$ an…
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We report on the electrical transport, magnetotransport, and magnetic properties studies on the transition metal dichalcogenides VSe$_2$ and VTe$_2$ and draw a comprehensive comparison between them. We observe Kondo effect in both systems induced by the exchange interaction between localized moments and conduction electrons at low temperature, resulting into resistance upturn at 6 K for VSe$_2$ and 17 K for VTe$_2$. From the field dependent resistance measurements we find that the data is fitted best with modified Hamann equation corrected by the quantum Brillouin function for VSe$_2$, while the data is fitted best with modified Hamann equation corrected by the classical Langevin function for VTe$_2$. Interestingly, we observe a contrasting magnetoresistance (MR) property between these systems across the Kondo temperature. That means, negative MR is found in both systems in the Kondo state. In the normal state MR is positive for VSe$_2$, while it is negligible for VTe$_2$. In addition, both systems show weak ferromagnetism at low temperature due to intercalated V atoms.
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Submitted 1 December, 2023;
originally announced December 2023.
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Weak Electronic Correlations Observed in Magnetic Weyl Semimetal Mn$_3$Ge
Authors:
Susmita Changdar,
Susanta Ghosh,
Anumita Bose,
Indrani Kar,
Achintya Low,
Patrick Le Fevre,
François Bertran,
Awadhesh Narayan,
Setti Thirupathaiah
Abstract:
Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations, we systematically studied the electronic band structure of Mn$_3$Ge in the vicinity of the Fermi level. We observe several bands crossing the Fermi level, confirming the metallic nature of the studied system. We further observe several flat bands along various high symmetry directions, consist…
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Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations, we systematically studied the electronic band structure of Mn$_3$Ge in the vicinity of the Fermi level. We observe several bands crossing the Fermi level, confirming the metallic nature of the studied system. We further observe several flat bands along various high symmetry directions, consistent with the DFT calculations. The calculated partial density of states (PDOS) suggests a dominant Mn $3d$ orbital contribution to the total valence band DOS. With the help of orbital-resolved band structure calculations, we qualitatively identify the orbital information of the experimentally obtained band dispersions. Out-of-plane electronic band dispersions are explored by measuring the ARPES data at various photon energies. Importantly, our study suggests relatively weaker electronic correlations in Mn$_3$Ge compared to Mn$_3$Sn.
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Submitted 1 December, 2023;
originally announced December 2023.
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Observation of Weak Kondo Effect and Angle Dependent Magnetoresistance in Layered Antiferromagnetic V$_5$S$_8$ Single Crystal
Authors:
Indrani Kar,
Sayan Routh,
Soumya Ghorai,
Shubham Purwar,
S. Thirupathaiah
Abstract:
The compound V$_5$S$_8$ can also be represented by V$_{1.25}$S$_2$, a transition metal dichalcogenide (TMDC) with excess V. Very few TMDCs show magnetism and/or Kondo effect. Among them, the sister compounds VSe$_2$ and VTe$_2$ are recently proved to show ferromagnetism in addition to the low-temperature resistivity upturn due to Kondo effect. In this study, we show Kondo effect in V$_5$S$_8$ orig…
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The compound V$_5$S$_8$ can also be represented by V$_{1.25}$S$_2$, a transition metal dichalcogenide (TMDC) with excess V. Very few TMDCs show magnetism and/or Kondo effect. Among them, the sister compounds VSe$_2$ and VTe$_2$ are recently proved to show ferromagnetism in addition to the low-temperature resistivity upturn due to Kondo effect. In this study, we show Kondo effect in V$_5$S$_8$ originated from the antiferromagnetic exchange interactions among the intercalated V atoms below the N$\acute{e}$el ($T_N$) temperature of 27 K. We find isotropic magnetic properties above $T_N$, while a strong magnetic anisotropy is noticed below $T_N$. In addition, below $T_N$ we find an out-of-plane ($H\parallel c$) spin-flop transition triggered at a critical field of 3.5 T that is absent from the in-plane ($H\perp c$). Angle-dependent magnetoresistance is found to be highly anisotropic in the antiferromagnetic state.
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Submitted 7 February, 2023;
originally announced February 2023.
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Effect on the Electronic and Magnetic Properties of Antiferromagnetic Topological Insulator MnBi$_2$Te$_4$ with Sn Doping
Authors:
Susmita Changdar,
Susanta Ghosh,
Kritika Vijay,
Indrani Kar,
Sayan Routh,
P. K. Maheswari,
Soumya Ghorai,
Soma Banik,
S. Thirupathaiah
Abstract:
We thoroughly investigate the effect of nonmagnetic Sn doping on the electronic and magnetic properties of antiferromagnetic topological insulator MnBi$_2$Te$_4$. We observe that Sn doping reduces the out-of-plane antiferromagnetic (AFM) interactions in MnBi$_2$Te$_4$ up to 68\% of Sn concentration and above the system is found to be paramagnetic. In this way, the anomalous Hall effect observed at…
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We thoroughly investigate the effect of nonmagnetic Sn doping on the electronic and magnetic properties of antiferromagnetic topological insulator MnBi$_2$Te$_4$. We observe that Sn doping reduces the out-of-plane antiferromagnetic (AFM) interactions in MnBi$_2$Te$_4$ up to 68\% of Sn concentration and above the system is found to be paramagnetic. In this way, the anomalous Hall effect observed at a very high field of 7.8 T in MnBi$_2$Te$_4$ is reduced to 2 T with 68\% of Sn doping. Electrical transport measurements suggest that all compositions are metallic in nature, while the low-temperature resistivity is sensitive to the AFM ordering and to the doping-induced disorder. Hall effect study demonstrates that Sn actually dopes electrons into the system, thus, enhancing the electron carrier density almost by two orders at 68\% of Sn. In contrast, SnBi$_2$Te$_4$ is found to be a p-type system. Angle-resolved photoemission spectroscopy (ARPES) studies show that the topological properties are intact at least up to 55\% of Sn as the Dirac surface states are present in the valance band, but in SnBi$_2$Te$_4$ we are unable to detect the topological states due to heavy hole doping. Overall, Sn doping significantly affects the electronic and magnetic properties of MnBi$_2$Te$_4$.
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Submitted 27 July, 2022;
originally announced July 2022.
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Experimental Evidence of Stable 2$H$ Phase on the Surface of Layered 1$T'$-TaTe$_2$
Authors:
Indrani Kar,
Kapildeb Dolui,
Luminita Harnagea,
Y. Kushnirenko,
G. Shipunov,
N. C. Plumb,
M. Shi,
B. Büchner,
S. Thirupathaiah
Abstract:
We report on the low-energy electronic structure of Tantalum ditelluride (1$T'$-TaTe$_2$), one of the charge density wave (CDW) materials from the group V transition metal dichalcogenides using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). We find that the Fermi surface topology of TaTe$_2$ is quite complicated compared to its isovalent compounds such as Ta…
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We report on the low-energy electronic structure of Tantalum ditelluride (1$T'$-TaTe$_2$), one of the charge density wave (CDW) materials from the group V transition metal dichalcogenides using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). We find that the Fermi surface topology of TaTe$_2$ is quite complicated compared to its isovalent compounds such as TaS$_2$, TaSe$_2$, and isostructural compound NbTe$_2$. More importantly, we discover that the surface electronic structure of 1$T'$-TaTe$_2$ has more resemblance to the 2$H$-TaTe$_2$, while the bulk electronic structure has more resemblance to the hypothetical 1$T$-TaTe$_2$. These experimental observations are thoroughly compared with our DFT calculations performed on 1$T$-, 2$H$- and 2$H$ (monolayer)/1$T$- TaTe$_2$. We further notice that the Fermi surface topology is temperature independent up to 180 K, confirming that the 2$H$ phase on the surface is stable up to 180 K and the CDW order is not due to the Fermi surface nesting.
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Submitted 22 December, 2020; v1 submitted 2 September, 2020;
originally announced September 2020.
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Metal-chalcogen bond-length induced electronic phase transition from semiconductor to topological semimetal in ZrX$_2$ (X = Se and Te)
Authors:
I. Kar,
Joydeep Chatterjee,
Luminita Harnagea,
Y. Kushnirenko,
A. V. Fedorov,
Deepika Shrivastava,
B. Büchner,
P. Mahadevan,
S. Thirupathaiah
Abstract:
Using angle resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations we studied the low-energy electronic structure of bulk ZrTe$_2$. ARPES studies on ZrTe$_2$ demonstrate free charge carriers at the Fermi level, which is further confirmed by the DFT calculations. An equal number of hole and electron carrier density estimated from the ARPES data, points ZrTe…
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Using angle resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations we studied the low-energy electronic structure of bulk ZrTe$_2$. ARPES studies on ZrTe$_2$ demonstrate free charge carriers at the Fermi level, which is further confirmed by the DFT calculations. An equal number of hole and electron carrier density estimated from the ARPES data, points ZrTe$_2$ to a semimetal. The DFT calculations further suggest a band inversion between Te $p$ and Zr $d$ states at the $Γ$ point, hinting at the non-trivial band topology in ZrTe$_2$. Thus, our studies for the first time unambiguously demonstrate that ZrTe$_2$ is a topological semimetal. Also, a comparative band structure study is done on ZrSe$_2$ which shows a semiconducting nature of the electronic structure with an indirect band gap of 0.9 eV between $Γ(A) $ and $M (L)$ high symmetry points. In the below we show that the metal-chalcogen bond-length plays a critical role in the electronic phase transition from semiconductor to a topological semimetal ingoing from ZrSe$_2$ to ZrTe$_2$.
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Submitted 9 July, 2019;
originally announced July 2019.