425
886-2-2789-8948
tklee [at] phys.sinica.edu.tw
425
886-2-2789-8948
tklee [at] phys.sinica.edu.tw
陳雯琪 / 886-2-2789-8948
(1) | 國內學術研究獎項 | 2019 | 台灣物理學會特殊貢獻獎 | |
(2) | 國內學術研究獎項 | 2018 | 中央研究院院士 | |
(3) | 國內學術研究獎項 | 2011-01 | 中華民國物理學會會士 | |
(4) | 其他國際學術研究獎項 | 2006 | Fellow,Institute of Physics, UK | |
(5) | 國內學術研究獎項 | 2005 | 侯金堆傑出榮譽獎 | |
(6) | 其他國際學術研究獎項 | 2004 | Fellow, American Physical Society | |
(7) | 國內學術研究獎項 | 2003 | 國科會傑出獎 | |
(8) | 國內學術研究獎項 | 1997 | 財團法人傑出人才講座 |
(1) | 西元年:2019 研究人員(中):李定國、杜韋霖 研究人員(英):LEE, TING-KUO, Wei-Lin Tu 研究成果名稱(中):銅氧超導體中配對序在贗能隙相與超導相之間的演化 研究成果名稱(英):Evolution of pairing orders between pseudogap and superconducting phases of cuprate superconductors 簡要記述(中):當溫度高於超導溫度且為低參雜時,存在於銅氧高溫超導體中的贗能隙相一直令人感到困惑。此相的特色是,在ARPES實驗中,動量空間裡部份的費米面會殘留(稱為費米弧),而其他部分的費米面會因能隙的產生而消失。當溫度低於超導溫度時,這些費米弧就轉變成d波的超導能隙。為了瞭解這個現象,我們研究一個低溫的強關聯模型,並且發現了一個特殊的相可以同時包含兩種配對序參量:其中一種序參量的古柏對總動量為零,而另一種的不為零。具有動量的配對態其配對序也會在空間上有所變化,也就是所謂的配對密度波 (PDW)。這些PDW同時也會和電荷密度與晶格內形狀因子的調制交織在一起。這兩種不同的配對序造成了一個像是有兩個能隙的能譜,而這樣的能譜正符合銅氧超導體上的ARPES實驗所觀察到的現象。當溫度上升時,零動量的配對序消失但是有限動量的配對序仍然存在,於是形成了費米弧。結果,我們所計算的準粒子能譜在不同參雜與溫度之下的行為的確與APPES及STS實驗所觀察到的現象相似。我們也更進一步討論了因為單向PDW造成的對稱破壞所導致的結果,以及在實驗上去探測這樣一個在贗能隙相中之PDW態的可能性。 簡要記述(英):One of the most puzzling problems of high temperature cuprate superconductor is the pseudogap phase (PG) at temperatures above the superconducting transition temperature in the underdoped regime. The PG phase is found by the angle-resolved photoemission spectra (ARPES) to have a gap at some regions in momentum space and a fraction of Fermi surface remained, known as Fermi arcs. The arc turns into a d-wave SC gap with a node below the SC transition temperature. Here, by studying a strongly correlated model at low temperatures, we obtained a phase characterized by two kinds of pairing order parameters with the total momentum of the Cooper pair to be zero and finite. The finite momentum pairing is accompanied with a spatial modulation of pairing order, i.e. a pair density wave (PDW). These PDW phases are intertwined with modulations of charge density and intra-unit cell form factors. The coexistence of the two different pairing orders provides the unique two-gaps like spectra observed by ARPES for superconducting cuprates. As temperature raises, the zero-momentum pairing order vanishes while the finite momentum pairing orders are kept, thus Fermi arcs are realized. The calculated quasiparticle spectra have the similar doping and temperature dependence as reported by ARPES and scanning tunneling spectroscopy (STS). The consequence of breaking symmetry between x and y due to the unidirectional PDW and the possibility to probe such a PDW state in the PG phase is discussed.
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(2) | 西元年:2017 研究人員(中):李定國、Peayush Choubey、杜韋霖、P J Hirschfeld 研究人員(英):LEE, TING-KUO, Peayush Choubey, Wei-Lin Tu and P J Hirschfeld 研究成果名稱(中):在t-t’-J模型中不相稱的電荷有序態 研究成果名稱(英):Incommensurate charge ordered states in the t-t’-J model 簡要記述(中):我們使用了Gutzwiller平均場論來研究t-t’-J模型在大尺度下的不相稱電荷有序態。我們特別探討了不相稱電荷調制態(incommensurate charge modulated states)的性質,而此態也就是文獻中所謂的點狀配對密度波(nPDW)態。此態混和了位置與連結的電荷序以及調制的d波配對序。其特色為具有均勻的配對振福以及晶格內d密度波形狀因子。我們的方法是利用Wannier函數來計算連續性的局部能量狀態密度(LDOS),以便與最近的BSCCO-2212銅氧超導體的STM實驗結果做比較。我們也對銅與氧的子晶格做傅立葉轉換來獲得晶格內形狀因子與空間的相差異。我們發現nPDW態的上述兩項性質與實驗資料十分吻合。我們也做了相稱電荷調制態的計算,並且發現結果與實驗不符。因此,我們認為nPDW態應該就是低參雜銅氧超導體在超導態中被實驗觀察到的電荷密度波相。 簡要記述(英):We study the incommensurate charge ordered states in the t – – t J ¢ model using the Gutzwiller mean field theory on large systems. In particular, we explore the properties of incommensurate charge modulated states referred to as nodal pair density waves(nPDW) in the literature. nPDW states intertwine site and bond charge order with modulated d-wave pair order, and are characterized by a nonzero amplitude of uniform pairing; they also manifest a dominant intra-unit cell d-density wave form factor. To compare with a recent scanning tunneling microscopy (STM)study (Hamidian et al 2015 Nat. Phys. 12 150) of the cuprate superconductor BSCCO-2212, we compute the continuum local density of states(LDOS) at a typical STM tip height using the Wannier function based approach. By Fourier transforming Cu and O sub-lattice LDOS we also obtain bias-dependent intra-unit cell form factors and spatial phase difference. We find that in the nPDW state the behavior of form factors and spatial phase difference as a function of energy agrees remarkably well with the experiment.This is in contrast to commensurate charge modulated states, which we show do not agree with experiment. We propose that the nPDW states are good candidates for the charge density wave phase observed in the superconducting state of underdoped cuprates.
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(3) | 西元年:2016 研究人員(中):李定國、杜韋霖 研究人員(英):LEE, TING-KUO, Wei-Lin Tu 研究成果名稱(中):高溫超導體中有序電荷態的起源 研究成果名稱(英):Genesis of charge orders in high temperature superconductors 簡要記述(中):銅氧高溫超導體的研究多態共存現象,一直都是十分令人困惑的。這些不同的態不僅包含了均勻的超導態與反鐵磁態,也包含許多低能量的有序電荷態,比如說單向的電荷密度波或是雙向的棋盤式密度結構。最近的實驗指出,在不同的銅氧超導體家族中,這些電荷密度波的晶格內形狀因子(intra-unit cell form factor)呈現出不同的對稱性。因此,我們利用重整化平均場理論來研究一個著名的描述銅氧超導體的強關聯模型。我們得到了很多不同的有序電荷態。這些不同的態不僅能量非常接近,並非由不同費米面來產生。我們得到的所有自洽解,都同時含有配對超導電子密度波與電荷密度波,其中的一些甚至還含有自旋密度波。隨著參雜度(doping)的增加,上述大部分的態都在低參雜區域(underdoped regime)內就消失了!只有一個具有高d-形狀因子的態在19%的電洞參雜度下才消失。這個19%與實驗上觀察到的現象是一致的。而且,經過一些特定的調整之後,這些態都會產生超導序。 簡要記述(英):One of the most puzzling facts about cuprate high-temperature superconductors in the lightly doped regime is the coexistence of uniform superconductivity and/or antiferromagnetism with many low-energy charge-ordered states in a unidirectional charge density wave or a bidirectional checkerboard structure. Recent experiments have discovered that these charge density waves exhibit different symmetries in their intra-unit-cell form factors for different cuprate families. Using a renormalized mean-field theory for a well-known, strongly correlated model of cuprates, we obtain a number of charge-ordered states with nearly degenerate energies without invoking special features of the Fermi surface. All of these self-consistent solutions have a pair density wave intertwined with a charge density wave and sometimes a spin density wave. Most of these states vanish in the underdoped regime, except for one with a large d-form factor that vanishes at approximately 19% doping of the holes, as reported by experiments. Furthermore, these states could be modified to have a global superconducting order, with a nodal-like density of states at low energy.
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(4) | 西元年:2010 研究人員(中):李定國、周崇斌、李定國 研究人員(英):LEE, TING-KUO, Chung-Pin Chou, T. K. Lee 研究成果名稱(英):Mechanism of formation of half-doped stripes in underdoped cuprates 簡要記述(英):Following our long term effort to understand the low energy phase of high temperature superconductors, recently we have studied the formation of stripe-like states in the t-J type models. In 2008 we found that these stripe states almost have the same energy as the uniform d-wave superconducting state. By using a variational Monte Carlo approach with this recently proposed stripe wave function, we showed that the strong correlation included in a t-J-type model has essentially all the necessary ingredients to form these stripes with modulations of charge density, spin magnetization, and pair field. If a perturbative effect of electron-phonon coupling to renormalize the effective mass or the hopping rate of holes is considered with the model, we find the half-doped stripes, which has on the average one half of a hole in one period of charge modulation, to be most stable energetic wise in the underdoped region, with doping concentration between 1/12 and 1/8. This is in good agreement with the observation in the neutron-scattering experiments.
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(5) | 西元年:2010 研究人員(中):李定國 研究人員(英):LEE, TING-KUO, Huaidong Jiang, Changyong Song, Chien-Chun Chen, Rui Xu, Kevin S. Raines, Benjamin P. Fahimian, Chien-Hung Lu,Ting-Kuo Lee, Akio Nakashima, Jun Urano, Tetsuya Ishikawa, Fuyuhiko Tamanoi, and Jianwei Miao 研究成果名稱(英):Quantitative 3D imaging of whole, unstained cells by using X-ray diffraction microscopy 簡要記述(英):Here, we report quantitative 3D imaging of a whole, unstained cell at a resolution of 50–60 nm by X-ray diffraction microscopy.We identified the 3D morphology and structure of cellular organelles including cell wall, vacuole, endoplasmic reticulum, mitochondria, granules, nucleus, and nucleolus inside a yeast spore cell. Furthermore, we observed a 3D structure protruding from the reconstructed yeast spore, suggesting the spore germination process. In collaboration with our experimental partners, we provide two theoretical tools for image reconstruction: the guided hybrid input0output method and the new alignment algorithm. These methods help to achieve improved resolution wiht only 25 projections used.
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(6) | 西元年:2008 研究人員(中):李定國、周崇斌、福島昇、李定國 研究人員(英):LEE, TING-KUO, Chung-Pin Chou, Noboru Fukushima, T. K. Lee 研究成果名稱(中):t-J 模型的非均勻態波函數 研究成果名稱(英):Clutser-glass wave function in the two-dimensional extended t-J model 簡要記述(中):高溫超導體有一個令人困惑現象,在低掺雜區超導態是一個非均勻態,由雜亂的線條態(stripe state)組成。這個現象常被用來質疑解釋高溫超導的t-J模型,需要考慮其他作用力來造成與超導競爭的不均勻相,而且這些作用力也可能是造成超導的機制而並非是很多人想到的superexchange作用力J。我們最近的工作(物理評論B78, 134530 (2008))大致解決了這個困難。 我們以共振價鍵(Resonating Valence Bond)的觀念發展出一個解釋線條態的波函數得到了很驚訝的結果,這些由雜亂線條態組成的不均勻態原來就是t-J模型該有的一些狀態,不需要加入其他的作用力來產生這些不均勻態,長距離的超導關聯性質並不受這些雜亂度(disorder)影響,而且它有node及線性態密度,這些不平常的結果都與實驗相符。 簡要記述(英):The presence of inhomogeneous states like periodic stripes or random-oriented stripe domains in high temperature superconductors has been used to argue against the simple t-J model as it seems to imply the existence of competing orders that could be generated by other interactions. Further more, these interactions could be the main origin of superconductivity mechanism instead of the super exchange interaction J as believed by many. This important but valid criticism on t-J type models has been resolved by us recently (Phys. Rev. B78, 134530 (2008)). We have proposed a wave function for the stripe state based on the resonating valence bond idea. A very surprising result is found. The presence of the inhomogeneous state with randomly oriented four-lattice-constant stripe domain is actually an inherent nature of the t-J model. There is no need to introduce a competing interaction to understand the existence of these glass-like states. The long-range pairing correlation is not much influenced by the disorder in the glass state which also has nodes and linear density of states. |