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Nai-Chang Yeh

Professor of Physics,
California Institute of Technology

Ph.D., Massachusetts Institute of Technology
B.Sc., National Taiwan University

Experiments in superconductivity, magnetism and other strongly correlated electronic systems such as graphene and carbon nanotubes; scanning probe microscopy; nano-science/technology; spintronics; organic semiconductors; low-temperature phases of helium; development of superconducting cavity-stabilized oscillators.


Group Photo

From left to right, front row: Slobodan, Prof. Yeh, Jenelyn, Peter; back row: Marcus, Cameron, Andrew, Nils, and Kevin

Recent research highlights


Local quasiparticle density of states and Fourier transformed local density of states in YBa2Cu3O7-δ (Y-123).


Local density of states in Y-123 at H = 5T. Fourier transformed local density of states in Y-123 at H = 5T.

Left image: The LDOS modulations of Y-123 at H = 5T and 6 K over a (22 x 29) nm2 area, showing patterns associated with density-wave modulations and vortices (circled objects) for ω = (a) -9 meV ~ -Δ', (b) -23 meV ~ -ΔSC, (c) -33 meV ~ -VCO and (d) -53 meV. We note that the vortex contrasts are the most apparent at |ω| <~ ΔSC and become nearly invisible for |ω| >>VCO. The vanishing contrast at high energies may be due to the onset of Cu-O optical phonons (~ 50 meV for the cuprates) so that both the collective modes and quasiparticles become scattered inelastically. Right image: FT studies of the conductance maps of Y-123: |F(k,ω)| at H = 5T and ω = -12 meV. We identify three sets of ω-independent wave-vectors in addition to the reciprocal lattice constants and the (π,π) resonance: QPDW and QCDW along (π,0)/(0,π) and QSDW along (π,π), which are circled for clarity. For more information on the measurements in the hole-type cuprate Y-123, please see arxiv:0906.1776 and arxiv:0808.3016. For more information on the vortex-state measurements in the infinite-layer electron-type cuprate La0.1Sr0.9CuO2 (La-112), please see arxiv:0809.0541.

Contact Information:

114 Sloan Annex
California Institute of Technology
MC 114-36
Pasadena, CA 91125
(626) 395-4313

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