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Lan YS, Chen CJ, Kuo SH, Lin YH, Huang A, Huang JY, Hsu PJ, Cheng CM, Jeng HT. Dual Dirac Nodal Line in Nearly Freestanding Electronic Structure of β-Sn Monolayer. ACS NANO 2024; 18:20990-20998. [PMID: 39086236 PMCID: PMC11328162 DOI: 10.1021/acsnano.4c01322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/02/2024]
Abstract
Two-dimensional topological insulators (2D TIs) have distinct electronic properties that make them attractive for various applications, especially in spintronics. The conductive edge states in 2D TIs are protected from disorder and perturbations and are spin-polarized, which restrict current flow to a single spin orientation. In contrast, topological nodal line semimetals (TNLSM) are distinct from TIs because of the presence of a 1D ring of degeneracy formed from two bands that cross each other along a line in the Brillouin zone. These nodal lines are protected by topology and can be destroyed only by breaking certain symmetry conditions, making them highly resilient to disorder and defects. However, 2D TNLSMs do not possess protected boundary modes, which makes their investigation challenging. There have been several theoretical predictions of 2D TNLSMs, however, experimental realizations are rare. β-Sn, a metallic allotrope of tin with a superconducting temperature of 3.72 K, may be a candidate for a topological superconductor that can host Majorana Fermions for quantum computing. In this work, single layers of α-Sn and β-Sn on a Cu(111) substrate are successfully prepared and studied using scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and density functional theory calculations. The lattice and electronic structure undergo a topological transition from 2D topological insulator α-Sn to 2D TNLSM β-Sn, with two types of nodal lines coexisting in monolayer β-Sn. Such a realization of two types of nodal lines in one 2D material has not been reported to date. Moreover, we also observed an unexpected phenomenon of freestanding-like electronic structures of β-Sn/Cu(111), highlighting the potential of ultrathin β-Sn films as a platform for exploring the electronic properties of 2D TNLSM and topological superconductors, such as few-layer superconducting β-Sn in lateral contact with topological nodal line single-layer β-Sn.
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Affiliation(s)
- Ye-Shun Lan
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chia-Ju Chen
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Shu-Hua Kuo
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yen-Hui Lin
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Angus Huang
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Center for Theory and Computation, National Tsing Hua University, Hsinchu 30013, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
| | - Jing-Yue Huang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Pin-Jui Hsu
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Center for Quantum Technology, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Horng-Tay Jeng
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
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Choi JR. Dynamics of Dispersive Measurements of Flux-Qubit States: Energy-Level Splitting Connected to Quantum Wave Mechanics. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2395. [PMID: 37686903 PMCID: PMC10490274 DOI: 10.3390/nano13172395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/09/2023] [Accepted: 08/16/2023] [Indexed: 09/10/2023]
Abstract
Superconducting flux qubits have many advantages as a storage of quantum information, such as broad range tunability of frequency, small-size fabricability, and high controllability. In the flux qubit-oscillator, qubits are connected to SQUID resonators for the purpose of performing dispersive non-destructive readouts of qubit signals with high fidelity. In this work, we propose a theoretical model for analyzing quantum characteristics of a flux qubit-oscillator on the basis of quantum solutions obtained using a unitary transformation approach. The energy levels of the combined system (qubit + resonator) are analyzed in detail. Equally spaced each energy level of the resonator splits into two parts depending on qubit states. Besides, coupling of the qubit to the resonator brings about an additional modification in the split energy levels. So long as the coupling strength and the tunnel splitting are not zero but finite values, the energy-level splitting of the resonator does not disappear. We conclude that quantum nondemolition dispersive measurements of the qubit states are possible by inducing bifurcation of the resonator states through the coupling.
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Affiliation(s)
- Jeong Ryeol Choi
- School of Electronic Engineering, Kyonggi University, Yeongtong-gu, Suwon 16227, Gyeonggi-do, Republic of Korea
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Thedford RP, Yu F, Tait WRT, Shastri K, Monticone F, Wiesner U. The Promise of Soft-Matter-Enabled Quantum Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2203908. [PMID: 35863756 DOI: 10.1002/adma.202203908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/14/2022] [Indexed: 06/15/2023]
Abstract
The field of quantum materials has experienced rapid growth over the past decade, driven by exciting new discoveries with immense transformative potential. Traditional synthetic methods to quantum materials have, however, limited the exploration of architectural control beyond the atomic scale. By contrast, soft matter self-assembly can be used to tailor material structure over a large range of length scales, with a vast array of possible form factors, promising emerging quantum material properties at the mesoscale. This review explores opportunities for soft matter science to impact the synthesis of quantum materials with advanced properties. Existing work at the interface of these two fields is highlighted, and perspectives are provided on possible future directions by discussing the potential benefits and challenges which can arise from their bridging.
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Affiliation(s)
- R Paxton Thedford
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York, 14853, USA
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, 14853, USA
| | - Fei Yu
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York, 14853, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, 14853, USA
| | - William R T Tait
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York, 14853, USA
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, 14853, USA
| | - Kunal Shastri
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York, 14853, USA
| | - Francesco Monticone
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York, 14853, USA
| | - Ulrich Wiesner
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York, 14853, USA
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Wong CH, Lortz R, Buntov EA, Kasimova RE, Zatsepin AF. A theoretical quest for high temperature superconductivity on the example of low-dimensional carbon structures. Sci Rep 2017; 7:15815. [PMID: 29150653 PMCID: PMC5693954 DOI: 10.1038/s41598-017-16038-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 11/07/2017] [Indexed: 11/13/2022] Open
Abstract
High temperature superconductivity does not necessarily require correlated electron systems with complex competing or coexisting orders. Instead, it may be achieved in a phonon-mediated classical superconductor having a high Debye temperature and large electronic density of states at the Fermi level in a material with light atoms and strong covalent bonds. Quasi-1D conductors seem promising due to the Van Hove singularities in their electronic density of states. In this sense, quasi-1D carbon structures are good candidates. In thin carbon nanotubes, superconductivity at ~15 K has been reported, and it is likely the strong curvature of the graphene sheet which enhances the electron-phonon coupling. We use an ab-initio approach to optimize superconducting quasi-1D carbon structures. We start by calculating a Tc of 13.9 K for (4.2) carbon nanotubes (CNT) that agrees well with experiments. Then we reduce the CNT to a ring, open the ring to form chains, optimize bond length and kink structure, and finally form a new type of carbon ring that reaches a Tc value of 115 K.
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Affiliation(s)
- C H Wong
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia
| | - R Lortz
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - E A Buntov
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia
| | - R E Kasimova
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia
| | - A F Zatsepin
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia.
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