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Controlling spin-orbit coupling to tailor type-II Dirac bands
Authors:
Nguyen Huu Lam,
Phuong Lien Nguyen,
Byoung Ki Choi,
Trinh Thi Ly,
Ganbat Duvjir,
Tae Gyu Rhee,
Yong Jin Jo,
Tae Heon Kim,
Chris Jozwiak,
Aaron Bostwick,
Eli Rotenberg,
Younghun Hwang,
Young Jun Chang,
Jaekwang Lee,
Jungdae Kim
Abstract:
NiTe2, a type-II Dirac semimetal with strongly tilted Dirac band, has been explored extensively to understand its intriguing topological properties. Here, using density-functional theory (DFT) calculations, we report that the strength of spin-orbit coupling (SOC) in NiTe2 can be tuned by Se substitution. This results in negative shifts of the bulk Dirac point (BDP) while preserving the type-II Dir…
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NiTe2, a type-II Dirac semimetal with strongly tilted Dirac band, has been explored extensively to understand its intriguing topological properties. Here, using density-functional theory (DFT) calculations, we report that the strength of spin-orbit coupling (SOC) in NiTe2 can be tuned by Se substitution. This results in negative shifts of the bulk Dirac point (BDP) while preserving the type-II Dirac band. Indeed, combined studies using scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES) confirm that the BDP in the NiTe2-xSex alloy moves from +0.1 eV (NiTe2) to -0.3 eV (NiTeSe) depending on the Se concentrations, indicating the effective tunability of type-II Dirac fermions. Our results demonstrate an approach to tailor the type-II Dirac band in NiTe2 by controlling the SOC strength via chalcogen substitution. This approach can be applicable to different types of topological materials.
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Submitted 22 October, 2023;
originally announced October 2023.
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Emergence of a Metal-Insulator Transition and High Temperature Charge Density Waves in VSe2 at the Monolayer Limit
Authors:
Ganbat Duvjir,
Byoung Ki Choi,
Iksu Jang,
Søren Ulstrup,
Soonmin Kang,
Trinh Thi Ly,
Sanghwa Kim,
Young Hwan Choi,
Chris Jozwiak,
Aaron Bostwick,
Eli Rotenberg,
Je-Geun Park,
Raman Sankar,
Ki-Seok Kim,
Jungdae Kim,
Young Jun Chang
Abstract:
Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe2 on graphe…
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Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe2 on graphene substrates. Angle-resolved photoemission spectroscopy (ARPES) uncovers that Fermi-surface nesting becomes perfect in ML VSe2. Renormalization group analysis confirms that imperfect nesting in three dimensions universally flows into perfect nesting in two dimensions. As a result, the charge density wave transition temperature is dramatically enhanced to a value of 350 K compared to the 105 K in bulk VSe2. More interestingly, ARPES and scanning tunneling microscopy measurements confirm an unexpected metal-insulator transition at 135 K, driven by lattice distortions. The heterointerface plays an important role in driving this novel metal-insulator transition in the family of monolayered transition metal dichalcogenides.
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Submitted 9 August, 2018;
originally announced August 2018.
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Universal renormalization group flow toward perfect Fermi-surface nesting driven by enhanced electron-electron correlations in monolayer vanadium diselenide
Authors:
Iksu Jang,
Ganbat Duvjir,
Byoung Ki Choi,
Jungdae Kim,
Young Jun Chang,
Ki-Seok Kim
Abstract:
In the present study we examine nature of a charge ordering transition in monolayer vanadium diselenide ($VSe_{2}$), which would be distinguished from that of $VSe_{2}$ bulk samples, driven by more enhanced electron-electron correlations. Recently, angle resolved photoemission spectroscopy measurements uncovered that the Fermi surface nesting becomes perfect, where the dynamics of hot electrons is…
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In the present study we examine nature of a charge ordering transition in monolayer vanadium diselenide ($VSe_{2}$), which would be distinguished from that of $VSe_{2}$ bulk samples, driven by more enhanced electron-electron correlations. Recently, angle resolved photoemission spectroscopy measurements uncovered that the Fermi surface nesting becomes perfect, where the dynamics of hot electrons is dispersionless along the orthogonal direction of the nesting wave-vector. In addition, scanning tunneling microscopy measurements confirmed that the resulting CDW state shows essentially the same modulation pattern as the three dimensional system of $VSe_{2}$. Here, we perform the renormalization group analysis based on an effective field theory in terms of critical CDW fluctuations and hot electrons of imperfect Fermi-surface nesting. As a result, we reveal that the imperfect nesting universally flows into perfect nesting in two dimensions, where the Fermi velocity along the orthogonal direction of the nesting vector vanishes generically. We argue that this electronic reconstruction is responsible for the observation that the CDW transition temperature is much more enhanced to be around $T_{c} > 300$ $K$ than that of the bulk sample.
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Submitted 22 October, 2018; v1 submitted 10 April, 2018;
originally announced April 2018.