中央研究院物理研究所

研究成果

期刊論文

[1] Joseph A. Hlevyack, Syu You Guan, Yen Chen Tsui, Chiao An Wang, Wen Yu Chen, Meng Kai Lin, Yao Li, Soorya Suresh Babu, Peng Chen, Ro Ya Liu, Ji Eun Lee, Jinwoong Hwang, Shujie Tang, Yang Bai, David Flötotto, Sung Kwan Mo, James N. Eckstein, Peter Abbamonte, Tien-Ming Chuang*, and Tai Chang Chiang*, 2025, “Topological Surface Superconductivity via Josephson Coupling in Bi2Te3/Nb”, Nano Letters, 25, 16387-16394. (SCIE) (IF: 9.6; SCI ranking: 13.7%,16.8%,12.9%,20%,10.1%,14.7%)
[2] Balaji Venkatesan, Syu-You Guan, Jen-Te Chang, Shiang-Bin Chiu, Po-Yuan Yang, Chih-Chuan Su, Tay-Rong Chang, Kalaivanan Raju, Raman Sankar, Somboon Fongchaiya, Ming-Wen Chu, Chia-Seng Chang, Guoqing Chang, Hsin Lin, Adrian Del Maestro, Ying-Jer Kao*, Tien-Ming Chuang*, 2025, “Direct Visualization of a Disorder Driven Electronic Smectic Phase in Nonsymmorphic Square-Net Semimetal GdSbTe”, NPJ QUANTUM MATERIALS, 10, 56. (SCIE) (IF: 5.4; SCI ranking: 29.5%,21.4%,26.5%,33.3%)
[3] R. Kalaivanan, Balaji Venkatesan, B. Dundi Sri Chandana, Rajesh Kumar Ulaganathan, G. Senthil Murugan, K. Moovendaran, Joydev Khatua, Li-Hsin Su, W. Zhou, Xiaofeng Xu, Chia-Seng Chang, Tien-Ming Chuang, Yoshiyuki Iizuka, I. Panneer Muthuselvam*, Horng-Tay Jeng*, Kwang-Yong Choi*, and Raman Sankar*, 2024, “Structural, magnetic, and electronic properties of a GdAsSe single crystal: Experimental and theoretical studies”, PHYSICAL REVIEW B, 109, 184420. (SCIE) (IF: 3.2; SCI ranking: 48.8%,34%,41.2%)
[4] Pei-Fang Chung & Balaji Venkatesan, Chih-Chuan Su, Jen-Te Chang, Hsu-Kai Cheng, Che-An Liu, Henry Yu, Chia-Seng Chang, Syu-You Guan, Tien-Ming Chuang*, 2024, “Design and performance of an ultrahigh vacuum spectroscopic-imaging scanning tunneling microscope with a hybrid vibration isolation system”, Review of Scientific Instruments, 95, 033701. (SCIE) (IF: 1.3; SCI ranking: 79.4%,79.2%)
[5] Ro-Ya Liu,* Angus Huang, Raman Sankar, Joseph Andrew Hlevyack, Chih-Chuan Su, Shih-Chang Weng, Meng-Kai Lin, Peng Chen, Cheng-Maw Cheng, Jonathan D. Denlinger, Sung-Kwan Mo, Alexei V. Fedorov, Chia-Seng Chang, Horng-Tay Jeng,* Tien-Ming Chuang, and Tai-Chang Chiang*, 2022, “Dirac Nodal Line in Hourglass Semimetal Nb3SiTe6”, NANO LETTERS, 23, 380-388. (SCIE) (IF: 9.6; SCI ranking: 13.7%,16.8%,12.9%,20%,10.1%,14.7%)
[6] Yun Yen, Cheng-Li Chiu, Ping-Hui Lin*, Raman Sankar, Tien-Ming Chuang* and Guang-Yu Guo, 2021, “Dirac nodal line and Rashba spin-split surface states in nonsymmorphic ZrGeTe”, New Journal of Physics, 23, 103019. (SCIE) (IF: 2.8; SCI ranking: 36.5%)
[7] Syu-You Guan, Peng-Jen Chen*, and Tien-Ming Chuang*, 2021, “Topological surface states and superconductivity in non-centrosymmetric PbTaSe2 (invited)”, JAPANESE JOURNAL OF APPLIED PHYSICS, 60, SE0803. (SCIE) (IF: 1.5; SCI ranking: 74.8%)
[8] Hsiao-Wen Chang, Vankayala Krishna Ranganayakulu, Syu-You Guan, Peng-Jen Chen, Min-Nan Ou, Yang-Yuan Chen, Tien-Ming Chuang, C.S. Chang, Maw-Kuen Wu and Ming-Jye Wang*, 2021, “Dense rotational twins in superconducting (111)-orientated $\delta$ -NbN epitaxial films on 4H-SiC substrates”, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 34, 045019. (SCIE) (IF: 3.7; SCI ranking: 30.8%,36.8%)
[9] Po-Hsun Wu, Ying-Ting Chan, Tzu-Chao Hung, Yi-Hui Zhang, Danru Qu*, Tien-Ming Chuang*, C. L. Chien, and Ssu-Yen Huang*, 2020, “Effect of demagnetization factors on spin current transport”, PHYSICAL REVIEW B, 102, 174426. (SCIE) (IF: 3.2; SCI ranking: 48.8%,34%,41.2%)
[10] Liang-Juan Chang, Jilei Chen, Danru Qu, Li-Zai Tsai, Yen-Fu Liu, Ming-Yi Kao, Jun-Zhi Liang, Tsuei-Shin Wu, Tien-Ming Chuang, Haiming Yu and Shang-Fan Lee*, 2020, “Spin wave injection and propagation in a magnetic nano-channel from a vortex core”, NANO LETTERS, 5, 3140. (SCIE) (IF: 9.6; SCI ranking: 13.7%,16.8%,12.9%,20%,10.1%,14.7%)
[11] Guan Syu-You, Liao Hsien-Shun, Juang Bo-Jing, Chin Shu-Cheng, Chuang Tien-Ming*, Chang Chia-Seng, 2019, “The design and the performance of an ultrahigh vacuum 3He fridge-based scanning tunneling microscope with a double deck sample stage for in-situ tip treatment”, Ultramicroscopy, 196 180-185. (SCIE) (IF: 2.1; SCI ranking: 37.5%)
[12] Nam Hyoungdo, Chen Hua, Adams Philip W., Guan Syu-You, Chuang Tien-Ming, Chang Chia-Seng, MacDonald Allan H., Shih Chih-Kang*, 2018, “Geometric quenching of orbital pair breaking in a single crystalline superconducting nanomesh network”, Nature Communications, 9(1). (SCIE) (IF: 14.7; SCI ranking: 8.3%)
[13] Chih-Chuan Su, Chi-Sheng Li, Tzu-Cheng Wang, Syu-You Guan, Raman Sankar, Fangcheng Chou, Chia-Seng Chang, Wei-Li Lee*, Guang-Yu Guo* and Tien-Ming Chuang*, 2018, “Surface termination dependent quasiparticle scattering interference and magneto-transport study on ZrSiS”, NEW JOURNAL OF PHYSICS, 20, 103025. (SCIE) (IF: 2.8; SCI ranking: 36.5%)
[14] Guan S.-Y., Chen P.-J., Chu M.-W., Sankar R., Chou F., Jeng H.-T., Chang C.-S., Chuang T.-M.*, 2016, “Superconducting topological surface states in the noncentrosymmetric bulk superconductor PbTaSe2”, Science Advances, 2(11) e1600894-e1600894. (SCIE) (IF: 11.7; SCI ranking: 11.1%)
[15] M. P. Allan, Kyungmin Lee, A. W. Rost, M. H. Fischer, F. Massee, K. Kihou, C-H. Lee, A. Iyo, H. Eisaki, T-M. Chuang, J. C. Davis and Eun-Ah Kim, 2015, “Identifying the ‘fingerprint’ of antiferromagnetic spin fluctuations in iron pnictide superconductors”, NATURE PHYSICS, 11, 177. (SCIE) (IF: 18.1; SCI ranking: 5.9%)
[16] M. P. Allan, T-M. Chuang, F. Massee, Yang Xie, Ni Ni, S. L. Bud'ko, G. S. Boebinger, Q. Wang, D. S. Dessau, P. C. Canfield, M. S. Golden & J. C. Davis*, 2013, “Anisotropic impurity states, quasiparticle scattering and nematic transport in underdoped $Ca(Fe_{1-x}Co_{x})_{2}As_{2}$ ”, Nature Physics, 9,220-224. (SCIE) (IF: 18.1; SCI ranking: 5.9%)
[17] M. P. Allan, A. W. Rost, A. P. Mackenzie, Yang Xie, J. C. Davis*, K. Kihou, C. H. Lee, A. Iyo, H. Eisak and T.-M. Chuang*, 2012, “Anisotropic Energy Gaps of Iron-Based Superconductivity from Intraband Quasiparticle Interference in LiFeAs”, SCIENCE, 336, 563-567. (SCIE) (IF: 44.8; SCI ranking: 2.8%)
[18] H. Berger, D. Ariosa, R. Gáal, A. Saleh, G. Margaritondo, S. F. Lee, S. H. Huang, H. W. Chang, T. M. Chuang, Y. Liou, Y. D. Yao, Y. Hwu, J. H. Je, L. V. Gasparov, D. B. Tanner, 2002, “Coexistence of ferromagnetism and high-temperature superconductivity in Dy-doped BiPbSrCaCuO”, SURFACE REVIEW AND LETTERS, 9, 1109. (SCIE) (IF: 1.2; SCI ranking: 92.5%,85.3%)
[19] T. M. Chuang, S. F. Lee, S. Y. Huang, Y. D. Yao, W. C. Cheng and G. R. Huang, 2002, “Anomalous Magnetic Moments in Co/Nb multilayers”, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 239,301. (SCIE) (IF: 2.5; SCI ranking: 61.1%,54.4%)
[20] S. F. Lee, T. M. Chuang, S. Y. Huang, W. L. Chang, and Y. D. Yao, 2001, “Two-dimensional to Three-dimensional Crossover and Magnetic Penetration Depth Study in NbTi/Co Multilayers”, JOURNAL OF APPLIED PHYSICS, 89, 7493. (SCIE) (IF: 2.7; SCI ranking: 42.1%)

發現與突破

[1] 西元年：2025
研究人員(中)：莊天明
研究人員(英)：TIEN-MING, CHUANG
研究成果名稱(中)：拓樸絕緣體/超導體薄膜中之拓樸表面超導與Josephson 耦合效應
研究成果名稱(英)：Topological Surface Superconductivity via Josephson Coupling in Bi2Te3/Nb films
簡要記述(中)：具備超導拓樸表面態的 Josephson元件被視為下世代超導量子位元的重要元件之一，有望提升量子運算所需的相干時間。然而，在多數實驗中，Josephson 耦合常被塊材載子(bulk carriers)所造成的近接效應所掩蓋，使其難以被直接觀測。在此國際合作研究，UIUC江台章教授團隊利用分子束磊晶技術成長於超導 Nb 基板上的拓樸絕緣體 Bi₂Te₃ 薄膜，實現了乾淨的 Josephson結構。Nb 中的超導庫柏電子對可穿隧過近乎絕緣的 Bi₂Te₃ ，並透過 Josephson 耦合在其拓樸表面態中誘發超導性。我們團隊利用自製低溫掃描穿隧顯微鏡，於T = 0.3 K下直接觀察到 Bi₂Te₃拓樸表面態中的超導能隙。值得注意的是，隨著 Bi₂Te₃ 薄膜厚度增加，儘管超導配對密度因穿隧機率降低而呈指數下降，但所誘發的能隙大小（約為 Nb 的 1/10）幾乎保持不變。這些實驗結果可由庫柏對經由Josephson 穿隧效應通過近乎絕緣的 Bi₂Te₃解釋，並在Bi₂Te₃表面形成單純之拓樸超導層。此成果突顯在拓樸元件中 Josephson 耦合對於狄拉克費米子長距離配對所扮演之關鍵角色。
簡要記述(英)：Josephson junctions incorporating superconducting topological surface states (TSS) emerge as promising building blocks for next-generation superconducting qubits, offering a potential pathway towards improved coherence for quantum computing. However, in most experiments, Josephson coupling is often obscured by other proximity effects associated with bulk carriers. In this work, we demonstrate such a junction using a topological insulator Bi₂Te₃ film epitaxially grown on a superconducting Nb substrate. Cooper pairs from Nb tunnel through the insulating Bi₂Te₃ layers and induce superconductivity in the TSS via Josephson coupling. Using scanning tunneling microscopy at T = 0.3 K, we observe a clear superconducting gap in the TSS of Bi₂Te₃. The induced gap (~1/10 of that of Nb) remains nearly constant as the Bi₂Te₃ film thickness increases, even though the superconducting pair density decreases exponentially. These observations can be understood via Josephson pair tunneling through the nearly insulating Bi2Te3 bulk, creating a pure topological superconducting sheet. Our findings underscore the essential role of Josephson coupling for long-range pairing in the spin-helical Dirac Fermions of topological structures.
This research is the result from the international collaboration between Dr. Tien-Ming Chuang’s group (Institute of Physics, Academia Sinica) and Prof. Tai-Chang Chiang’s group (University of Illinois Urbana-Champaign). The work at the Institute of Physics was supported by the National Science and Technology Council and Academia Sinica.

主要相關著作：

Joseph A. Hlevyack, Syu You Guan, Yen Chen Tsui, Chiao An Wang, Wen Yu Chen, Meng Kai Lin, Yao Li, Soorya Suresh Babu, Peng Chen, Ro Ya Liu, Ji Eun Lee, Jinwoong Hwang, Shujie Tang, Yang Bai, David Flötotto, Sung Kwan Mo, James N. Eckstein, Peter Abbamonte, Tien-Ming Chuang*, and Tai Chang Chiang*, 2025, “Topological Surface Superconductivity via Josephson Coupling in Bi2Te3/Nb”, Nano Letters, 25, 16387-16394. (SCIE) (IF: 9.6; SCI ranking: 13.7%,16.8%,12.9%,20%,10.1%,14.7%)

[2] 西元年：2025
研究人員(中)：莊天明
研究人員(英)：TIEN-MING, CHUANG
研究成果名稱(中)：拓樸節線半金屬GdSbTe中發現電子液晶相
研究成果名稱(英)：Discovery of a disorder-driven electronic smectic phase in weakly correlated Dirac nodal line semimetal GdSbTe
簡要記述(中)：電子在固體中有時會自發排列並打破原本晶體的對稱性，形成類似液晶分子的特殊量子態。這種被稱為「電子液晶相」的現象，通常出現在電子間具有強交互作用的強關聯電子系統中，例如高溫銅氧化物超導體。然而，我們的研究團隊在一種弱關聯性的狄拉克節線半金屬 GdSbTe 中，意外發現了「層列型電子相（smectic phase）」。我們利用掃描式穿隧顯微鏡直接觀察到這種對稱性破壞的量子相，並在原子尺度下證明化學摻雜在其中扮演了關鍵角色。這項發現不僅深化了我們對電子液晶相微觀機制的理解，也提供了一個全新的材料平台，讓研究人員能進一步探索無序雜質、狄拉克費米子與電子關聯之間的相互作用。
本研究由國際團隊共同完成，包括中央研究院物理研究所莊天明博士、林新博士、Raman Sankar 博士，成功大學張泰榕教授、美國田納西大學 Adrian Del Maestro 教授、台灣大學朱明文博士及高英哲教授。中央研究院的研究工作由材料與分析科技探索計畫（iMATE）、尖端晶體材料開發及製作計畫與國家科學及技術委員會支持。
簡要記述(英)：Electrons in solids can organize into unusual patterns, similar to liquid crystals, by breaking the crystalline symmetry of the host material. These so-called electronic liquid crystal phases usually appear in strongly correlated electron systems, such as high Tc cuprate superconductors.
Surprisingly, we have discovered such an electronic smectic phase in weakly correlated Dirac nodal line semimetal GdSbTe, using scanning tunneling microscopy. We demonstrate that chemical substitutions play a key role in creating these symmetry-breaking quantum phases.
Our findings advance the microscopic understanding of electronic liquid crystal phases in quantum materials and present a novel platform for exploring the interplay among quenched disorder, Dirac fermions and electron correlation.
This research was carried out by an international team, including Dr. Tien-Ming Chuang (IOP), Dr. Hsin Lin (IOP), Dr. Raman Sankar (IOP), Prof. Tay-Rong Chang (NCKU), Prof. Adrian Del Maestro (U Tennessee), Prof. Ming-Wen Chu (NTU), and Dr. Ying-Jer Kao (NTU). The work at the IOP was supported by Innovative Materials and Analytical Technology Exploration (iMATE) Program and the National Science and Technology Council.

主要相關著作：

Balaji Venkatesan, Syu-You Guan, Jen-Te Chang, Shiang-Bin Chiu, Po-Yuan Yang, Chih-Chuan Su, Tay-Rong Chang, Kalaivanan Raju, Raman Sankar, Somboon Fongchaiya, Ming-Wen Chu, Chia-Seng Chang, Guoqing Chang, Hsin Lin, Adrian Del Maestro, Ying-Jer Kao*, Tien-Ming Chuang*, 2025, “Direct Visualization of a Disorder Driven Electronic Smectic Phase in Nonsymmorphic Square-Net Semimetal GdSbTe”, NPJ QUANTUM MATERIALS, 10, 56. (SCIE) (IF: 5.4; SCI ranking: 29.5%,21.4%,26.5%,33.3%)

[3] 西元年：2018
研究人員(中)：莊天明、Hyoungdo Nam, Hua Chen, Philip W. Adams, Syu-You Guan, Tien-Ming Chuang, Chia-Seng Chang, Allan H. MacDonald & Chih-Kang Shih
研究人員(英)：TIEN-MING, CHUANG, Hyoungdo Nam, Hua Chen, Philip W. Adams, Syu-You Guan, Tien-Ming Chuang, Chia-Seng Chang, Allan H. MacDonald & Chih-Kang Shih
研究成果名稱(中)：奈米超薄網格結構提供增強超導臨界磁場之新方法
研究成果名稱(英)：Nanoscale ultra-thin film network provides a novel approach to enhance the critical field of superconductors
簡要記述(中)：超導體在高磁場下維持其超導特性的能力對其應用至關重要。物理所表面組參與國際合作發現了一種提升超導體臨界磁場的方法。研究人員使用分子束磊晶技術將鉛生長成2nm厚的單晶奈米網格後，藉由低溫掃描穿隧顯微鏡、互感和電性傳輸測量發現樣品保持極強的巨觀相位剛性(phase rigidity)，進而保持樣品超導溫度(Tc)仍然接近塊材之Tc。同時由於超薄幾何結構和強自旋軌道耦合的關係，鉛奈米網格之平行臨界磁場明顯高於Clogston極限。而在垂直磁場下，軌道配對破壞效應也被抑制，直到磁長度小於奈米網格的橫向尺寸。網格橫向寬度與垂直臨界磁場的逆相關顯示此方法可能進一步提高垂直臨界磁場。這項工作展示類似奈米結構可用來優化超導量子元件特性。
簡要記述(英)：The ability for a superconductor to survive under high magnetic fields is crucial for its applications. A team of researchers from US and Academia Sinica has found a method to boost the critical field of superconductor. The researchers used the molecular beam epitaxial (MBE) technique to grow the single crystalline Pb into a nano-mesh of 2nm thickness. By using low temperature scanning tunneling microscope, mutual inductance measurements and magneto-transport measurements, the researchers found that the Pb nano-mesh maintains strong global phase rigidity, thus retaining the Tc close to that of a bulk crystal. The parallel critical field is significantly higher than the Clogston limit as a direct consequence of ultra-thin geometry and strong spin orbital coupling. In the perpendicular field, the orbital pair breaking is also quenched until the magnetic length becomes smaller than the lateral dimension of the nano-mesh. The inverse correlation of the lateral width and local HC⏊ points to a possibility to achieve much higher HC⏊. This work demonstrates that superconductivity pair breaking can be significantly suppressed by nanoscale engineering and opens new strategies to optimize superconducting quantum devices.
These findings have now been published in the journal Nature Communication. The collaboration consists of Prof. Chih-Kang Shih (University of Texas), Prof. Allan MacDonald (University of Texas), Prof. Hua Chen (Colorado State University), Prof. Philip Adams (Louisiana State University) and the Surface Science Group at the Institute of Physics, Academia Sinica (Dr. Syu-You Guan, Dr. Tien-Ming Chuang and Director Chia-Seng Chang). The work at Institute of Physics is supported by Ministry of Science and Technology and Academia Sinica. Dr. Tien-Ming Chuang also acknowledges the support from Kenda Foundation and Dr. Syu-You Guan is now the recipient of postdoctoral fellowship from Academia Sinca.

主要相關著作：

Nam Hyoungdo, Chen Hua, Adams Philip W., Guan Syu-You, Chuang Tien-Ming, Chang Chia-Seng, MacDonald Allan H., Shih Chih-Kang*, 2018, “Geometric quenching of orbital pair breaking in a single crystalline superconducting nanomesh network”, Nature Communications, 9(1). (SCIE) (IF: 14.7; SCI ranking: 8.3%)

[4] 西元年：2016
研究人員(中)：莊天明、關旭佑、陳鵬仁、朱明文、雷曼、周方正、鄭弘泰、張嘉升
研究人員(英)：TIEN-MING, CHUANG, Syu-You Guan,Peng-Jen Chen,Ming-Wen Chu,Raman Sankar,Fangcheng Chou,Horng-Tay Jeng, Chia-Seng Chang
研究成果名稱(中)：發現非中心對稱PbTaSe2單晶中之超導拓樸態
研究成果名稱(英)：Discovery of superconducting topological surface states in PbTaSe2
簡要記述(中)：當拓樸絕緣體結合超導體時，理論上可形成拓樸超導體。在拓樸超導體中，尚未確認的費米子-馬約拉那費米子，會被束縛在如超導渦流的拓樸缺陷，這樣的組合被預測會表現出非阿貝爾統計，可成為量子計算的基礎。在拓樸絕緣體中引入超導的最簡單方法是將其摻雜出超導性或於其上覆蓋s-波超導體。然而摻雜難以製造出均勻有序的材料，在多層結構中製造出乾淨的界面也相當困難。

解決之道是尋找適合的符合化學配比超導體，費米面上展現出拓樸表面態，並在超導態時，具有完整超導能隙。到目前為止，尚未有這種物質被發現。由本院物理所陳鵬仁博士和清大鄭弘泰教授透過密度泛函計算研究PbTaSe2的電子結構，發現其能滿足成為拓樸超導體的條件。材料由台大凝態中心Raman Sankar博士和研究員周方正成功合成出高品質單晶樣品，並由該中心研究員朱明文使用掃描穿透式電子顯微鏡確認晶體結構。表面與電子結構則由台大物理所博士生關旭佑、本院物理所張嘉升博士和莊天明博士使用掃描穿隧電子顯微鏡觀察原子尺度下電子波函數變化，確認了理論預測中拓樸能帶的能譜特徵和超導特性。此成果為在符合化學配比的塊材中，首次發現到具有完整超導能隙的拓樸表面態。此成果展示PbTaSe2是一個值得重視的拓樸超導體候選材料。
簡要記述(英)：The search of novel states of matter has always been of fundamental and technical importance. For example, the study of spin order in magnetic materials has led to the giant magnetoresistance (Nobel Prize in 2007) and the miniaturization of hard drives. The discovery of the quantum Hall effect in 1980 (Nobel Prize in 1985) and the subsequent development of topological band theory (Nobel Prize this year) have open a new field to the study of topological phases. The key development is the theoretical prediction and the experimental confirmation of topological insulators (TIs). A TI, like an ordinary insulator, has a bulk energy gap separating the highest valence band from the lowest conduction band. However, at the boundary, a TI has protected conducting states that are immune to impurities and useful for high performance electronics.
When a TI combined with superconductivity, it can theoretically lead to another important class of materials: topological superconductors (TSCs). TSCs are characterized by a full superconducting gap in the bulk and topologically protected gapless surface states. In a TSC, Majorana fermion, a hypothetical particle is its own anti-particle, is bound to a topological defect such as a superconducting vortex. Such combined objects are predicted to exhibit non-Abelian statistics and to form the basis of the fault-tolerant quantum computation. The simplest way to introduce superconductivity in a TI is by making it superconducting by doping or by coating a layer of s-wave superconductor. However, both approaches are technically challenging because it is difficult to make a homogenous doped material or a heterostructure with a clean interface.
The solution is to find a stoichiometric material that exhibits topological surface states at Fermi level in the normal state combined with fully gapped bulk superconductivity below TC. So far, no such a bulk material is reported. Dr. Peng-Jen Chen from AS and Prof. Horng-Tay Jeng from NTHU found such requirements for a TSC are satisfied in a layered material, PbTaSe2 when studying its electronic structures by density functional theory. High quality single crystals are then synthesized by Dr. Raman Sankar and Dr. Fangcheng Chou at Center for Condensed Matter Sciences, NTU and the detailed crystal structure is confirmed by Dr. Ming-Wen Chu by using scanning transmission electron microscopy. By visualizing the electron wavefunction at atomic scale with the state-of-the-art home-built scanning tunneling microscopes, PhD student Syu-You Guan from NTU, Dr. Chia-Seng Chang and Dr. Tien-Ming Chuang from AS confirm the spectroscopic signature of the calculated topological band structures and superconducting properties in PbTaSe2. The fully gapped superconducting topological surface state is reported for the first time in a stoichiometric bulk material. Their work shows PbTaSe2 is a promising TSC candidate.
This research was supported by Academia Sinica, Ministry of Science and Technology, and National Taiwan University. Dr. Tien-Ming Chuang also received the support from Kenda Foundation.

主要相關著作：

Guan S.-Y., Chen P.-J., Chu M.-W., Sankar R., Chou F., Jeng H.-T., Chang C.-S., Chuang T.-M.*, 2016, “Superconducting topological surface states in the noncentrosymmetric bulk superconductor PbTaSe2”, Science Advances, 2(11) e1600894-e1600894. (SCIE) (IF: 11.7; SCI ranking: 11.1%)

[5] 西元年：2013
研究人員(中)：莊天明
研究人員(英)：TIEN-MING, CHUANG
研究成果名稱(中)：鐵基超導體中異向性雜質態, 準粒子干涉與向列型電子傳輸之關聯性
研究成果名稱(英)：Anisotropic impurity states, quasiparticle scattering and nematic transport in underdoped Ca(Fe_{1-x}Co_{x})_{2}As_{2}
簡要記述(中)：鐵基超導體的超導現象可由對其反鐵磁/正交晶母相摻入雜質所產生. 這些雜質在原子尺度下對電子結構的影響雖然已有許多不同理論, 然而實驗上的觀察卻闕之付如. 巨觀上我們目前知道在母相中電子傳輸有很強的異向性, 在b軸方向電阻較高, 並隨著雜質濃度而改變, 母相在超導溫度最高的雜質濃度會被完全破壞後, 這個’向列型’電子結構也隨之消失. 藉由掃描式穿隧電流顯微鏡, 我們可以直接觀察到當鈷原子取代鐵原子時, 母相的電子結構產生許多相同的異向性雜質態. 每個異向性雜質態具有約8倍鐵原子的晶格間距, 在空間中沿著a軸方向排列, 隨機分布. 我們也展示這些異向性雜質態可以散射電子造成傳輸實驗中所觀察到的’向列型’ 電子結構. 我們的結果顯示雜質對鐵基超導體的母相有顯著的影響.
簡要記述(英)：Iron-based high-temperature superconductivity develops when the ‘parent’ antiferromagnetic/orthorhombic phase is suppressed, typically by introduction of dopant atoms. But their impact on atomic-scale electronic structure, although in theory rather complex, is unknown experimentally. What is known is that a strong transport anisotropy with its resistivity maximum along the crystal b axis, develops with increasing concentration of dopant atoms; this ‘nematicity’ vanishes when the parent phase disappears near the maximum superconducting Tc. The interplay between the electronic structure surrounding each dopant atom, quasiparticle scattering therefrom and the transport nematicity has therefore become a pivotal focus of research into these materials. Here, by directly visualizing the atomic-scale electronic structure, we show that substituting Co for Fe atoms in underdoped Ca(Fe_{1-x}Co_{x})_{2}As_{2} generates a dense population of identical anisotropic impurity states. Each is ~8 Fe–Fe unit cells in length, and all are distributed randomly but aligned with the antiferromagnetic a axis. By imaging their surrounding interference patterns, we further demonstrate that these impurity states scatter quasiparticles in a highly anisotropic manner, with the maximum scattering rate concentrated along the b axis. These data provide direct support for the recent proposals that it is primarily anisotropic scattering by dopant-induced impurity states that generates the transport nematicity; they also yield simple explanations for the enhancement of the nematicity proportional to the dopant density and for the occurrence of the highest resistivity along the b axis.

主要相關著作：

M. P. Allan, T-M. Chuang, F. Massee, Yang Xie, Ni Ni, S. L. Bud'ko, G. S. Boebinger, Q. Wang, D. S. Dessau, P. C. Canfield, M. S. Golden & J. C. Davis*, 2013, “Anisotropic impurity states, quasiparticle scattering and nematic transport in underdoped $Ca(Fe_{1-x}Co_{x})_{2}As_{2}$ ”, Nature Physics, 9,220-224. (SCIE) (IF: 18.1; SCI ranking: 5.9%)

[6] 西元年：2012
研究人員(中)：莊天明
研究人員(英)：TIEN-MING, CHUANG, M. P. Allan, A. W. Rost, A. P. Mackenzie, Yang Xie, J. C. Davis, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki
研究成果名稱(中)：鐵基高溫超導體之超導能隙異向性研究
研究成果名稱(英)：Anisotropic Energy Gaps of Iron-based Superconductivity from Intraband Quasiparticle Interference in LiFeAs
簡要記述(中)：超導體中，電子會形成庫柏電子對，在晶格中移動時不會產生電阻。來自台、日、英、美的研究團隊，藉由量測鐵基超導體中庫柏電子對的內部電子聯結強度，證實磁性對高溫超導具有關鍵性的影響。實驗也檢驗此強度與電子移動方向的關聯性，進一步驗證了理論的預測。我們希望未來這類理論可用在檢視及設計更高溫的超導體。此研究成果發表在「科學」期刊（Science 336, 563 (2012)）。

高溫超導成因已困惑了科學家近三十年。許多人相信藉磁性媒介的電子間交互作用是關鍵。於2008年發現的鐵基超導體為這個想法提供了另一個有力證據，因為它們的母系化合物像銅基高溫超導體有類似反鐵磁性。但決定磁性在鐵基超導的角色是個複雜問題，因為每個鐵原子有五個電子貢獻磁性。為查明是否電子間磁交互作用產生超導，必須量測超導能隙異向性。此物理量可顯示庫柏電子對在動量空間中不同方向的鍵結強度。

理論學家們針對以磁性為主的電子配對機制發展出不同的高溫超導理論，並預測符合這些理論的實驗結果將會是如何。研究團隊發現實驗結果吻合理論預測的特徵。本文共同通訊作者院莊天明博士指出「儘管理論學家預測超導能隙異向性的存在，但由於複雜的電子結構，計算這效應的大小仍是非常的困難。我們的量測結果不僅在定性上與理論預測吻合，並且提供理論學家關鍵資訊以發展定量的高溫超導理論。」

簡要記述(英)：In superconductors, electrons form Cooper pairs and move through the crystal lattice without resistance. By measuring how strongly Cooper pairs are bound together in an iron-based superconductor, scientists from Academia Sinica, the University of St Andrews, Cornell University, the U.S. Department of Energy’s Brookhaven National Laboratory and AIST, Japan, provide direct evidence supporting theories in which magnetism holds the key to this material’s ability to carry current with no resistance. The measurements take into account the directions in which the electrons are traveling, which was central to testing the theoretical predictions, thereby strengthening confidence that this type of theory may one day be used to identify or design new materials with improved properties - namely, superconductors operating at room temperatures. The findings are published in Science 336, 563 on May 4, 2012.

High-temperature superconductors have been fascinating to both scientists and engineers since they could carry current with no loss at temperatures as high as 155 K. The hope is that understanding the physics of these compounds will lead to the design of superconductors able to operate at room temperatures, which can be used for energy-saving technologies, such as zero-lose power transmission lines. However, the physics of high temperature superconductivity has confounded scientists over the last 30 years. It is generally believed that the magnetically mediated electron-electron interaction of these materials is the key. When iron-based superconductors were discovered in 2008, this idea received a big boost because their parent compounds exhibit similar magnetic properties as their copper-based counterparts. However, determining that role is a very complex problem. In each iron atom there are five magnetic electrons. In order to find out if the magnetic interactions between electrons are generating the superconductivity, one has to measure what’s called the anisotropic superconducting energy gap, which can tell scientists the bounding strength of Cooper pairs along different directions in momentum space.

Their method, multi-band Bogoliubov quasiparticle scattering interference, found the “signature” predicted by magnetism-based pairing theory. "Although theorists predicted the existence of superconducting gap anisotropy, it’s difficult to calculate how large this effect is. Our measurements not only agree with the theoretical prediction but also provide theorists with crucial information towards a more quantified description." said Dr. Tien-Ming Chuang of Academia Sinica. The next step is to use the same technique to determine whether the theory holds true for other iron superconductors.

主要相關著作：

M. P. Allan, A. W. Rost, A. P. Mackenzie, Yang Xie, J. C. Davis*, K. Kihou, C. H. Lee, A. Iyo, H. Eisak and T.-M. Chuang*, 2012, “Anisotropic Energy Gaps of Iron-Based Superconductivity from Intraband Quasiparticle Interference in LiFeAs”, SCIENCE, 336, 563-567. (SCIE) (IF: 44.8; SCI ranking: 2.8%)

(1)	國內學術研究獎項	2018	科技部優秀年輕學者研究計畫
(2)		2017	科技部吳大猷先生紀念獎
(3)	國內學術研究獎項	2012	建大文教基金會傑出年輕金玉學者獎

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