Direct Observation of Nodal Quasiparticles in the Non-Magnetic Superconductors Yttrium(lutetium)nickel-Boron-Carbon Field-Angle Dependent Heat Capacity

Park, Tuson

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Description

Title

Direct Observation of Nodal Quasiparticles in the Non-Magnetic Superconductors Yttrium(lutetium)nickel-Boron-Carbon Field-Angle Dependent Heat Capacity

Author(s)

Park, Tuson

Issue Date

2003

Doctoral Committee Chair(s)

Salamon, Myron B.

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Engineering, Materials Science

Language

eng

Abstract

The gap function in unconventional superconductors may vanish at points or lines in momentum space, permitting electronic excitations, termed nodal quasiparticles, to exist at temperatures well below the superconducting transition. In the vortex phase, the presence of nodal quasiparticles should be directly observable through the variation of the heat capacity with the angle between a magnetic field and the location of the zeroes of the gap. The heat capacity of candidate non-magnetic unconventional superconductors YNi2B 2C and LuNi2B2C were found to exhibit fourfold oscillations with field angle, the first such observation. The observed angular variations are in quantitative agreement with theory, confirming that quasiparticles are created via Doppler shifts at a line of zeros normal to . These results demonstrate that field-angle-dependent heat capacity can be a powerful tool in probing the momentum-space gap structure in unconventional superconductors such as high Tc cuprates, borocarbides, etc.

Graduation Semester

2003

Type of Resource

text

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