Browsing by Author "Lee, Ting-Kuo"

Now showing 1 - 4 of 4

Detecting small lung tumors in mouse models by refractive-index microradiology
(2011-08-01)
Chien, Chia-Chi
;
Zhang, Guilin
;
Hwu, Y.
;
Liu, Ping
;
Yue, Weisheng
Refractive-index (phase-contrast) radiology was able to detect lung tumors less than 1 mm in live mice. Significant micromorphology differences were observed in the microradiographs between normal, inflamed, and lung cancer tissues. This was made possible by the high phase contrast and by the fast image taking that reduces the motion blur. The detection of cancer and inflammation areas by phase contrast microradiology and microtomography was validated by bioluminescence and histopathological analysis. The smallest tumor detected is less than 1 mm(3) with accuracy better than 1 x 10(-3) mm(3). This level of performance is currently suitable for animal studies, while further developments are required for clinical application.
Emergence of a Fermionic Finite-Temperature Critical Point in a Kondo Lattice
(2016-04-27)
Chou, Po-Hao
;
Zhai, Liang-Jun
;
Chung, Chung-Hou
;
Mou, Chung-Yu
;
Lee, Ting-Kuo
The underlying Dirac point is central to the profound physics manifested in a wide class of materials. However, it is often difficult to drive a system with Dirac points across the massless fermionic critical point. Here by exploiting screening of local moments under spin-orbit interactions in a Kondo lattice, we show that below the Kondo temperature, the Kondo lattice undergoes a topological transition from a strong topological insulator to a weak topological insulator at a finite temperature T-D. At T-D, massless Dirac points emerge and the Kondo lattice becomes a Dirac semimetal. Our analysis indicates that the emergent relativistic symmetry dictates nontrivial thermal responses over large parameter and temperature regimes. In particular, it yields critical scaling behaviors both in magnetic and transport responses near T-D.
Enhanced quantum oscillations in Kondo insulators
(2020-03-02)
Lu, Yen-Wen
;
Chou, Po-Hao
;
Chung, Chung-Hou
;
Lee, Ting-Kuo
;
Mou, Chung-Yu
Quantum oscillations have long been regarded as the manifestation of the Fermi surface in metals. However, they were recently observed in Kondo insulators. We examine the Kondo screening due to Landau levels in Kondo insulators. It is shown that, even for large Kondo insulating gaps, appreciable amplitudes of quantum oscillations that are consistent with experimental observations are present both in magnetization and resistivity. Specifically, we show that, due to the periodic alignment between the Landau levels in the conduction and the f-orbit electrons, the Kondo screening itself undergoes oscillations so that the electronic structure oscillates with the magnetic field. Our results explain main features of quantum oscillations observed in experiments. They indicate that the nonrigidity of the electronic structure results in observable quantum oscillation Kondo insulators. This effect provides a way to probe the Fermi surface geometry of insulators.
Strain-induced superconducting pair density wave states in graphene
(2018-11-02)
Xu, Feng
;
Chou, Po-Hao
;
Chung, Chung-Hou
;
Lee, Ting-Kuo
;
Mou, Chung-Yu
Graphene is known to be nonsuperconducting. However, surprising superconductivity is recently discovered in a flat band in a twisted bilayer graphene. Here, we show that superconductivity can be more easily realized in topological flat bands induced by strain in graphene through periodic ripples. Specifically, it is shown that by including correlation effects, the chiral d-wave superconductivity can be stabilized under strain even for slightly doped graphene. The chiral d-wave superconductivity generally coexists with charge density waves (CDW) and pair density waves (PDW) of the same period. Remarkably, a pure PDW state with doubled period that coexists with the CDW state is found to emerge at a finite-temperature region under reasonable strain strength. The emergent PDW state is shown to be superconducting with nonvanishing superfluid density, and it realizes the long-sought-after superconducting states with nonvanishing center-of-mass momentum for Cooper pairs.