Condensed-Matter Physics & Materials Science Seminar
"Mechanism of strange metal and strange metal state near a heavy fermion quantum critical point"
Presented by Chung-Hou Chung, Department of Electrophysics, National Chiao-Tung University, Taiwan
Wednesday, July 18, 2018, 1:30 pm — ISB Bldg. 734 Conference Room 201
Strange metal (SM) behaviors with non-Fermi liquid (NFL) properties, generic features of heavy fermion systems near quantum phase transitions, are yet to be understood microscopically. A paradigmatic example is the magnetic field-tuned quantum critical heavy fermion metal YbRh2Si2 (YRS), revealing a possible SM state over a finite range of fields at low temperatures when substituted with Ge. Above a critical field, the SM state gives way to a heavy Fermi liquid with Kondo correlation. The NFL behavior shows most notably a linear-in-temperature electrical resistivity and a logarithmic-in-temperature followed by a power-law-in-temperature in the specific heat coefficient at low temperatures . We propose a mechanism to explain it: a quasi-2d fluctuating anti-ferromagnetic short-range resonating-valence-bond (RVB) spin-liquid competing with the Kondo correlation (Fig. 1) . Applying renormalization group analysis on an effective field theory beyond a large-N approach to an antiferromagnetic Kondo-Heisenberg model, we identify the critical point, and explain remarkably well the SM behavior. Our theory goes beyond the well-established framework of quantum phase transitions and serves as a new basis to address open issues of the non-Fermi liquid behavior in quantum critical heavy-fermion compounds, such as: the strange superconductivity observed in the "115" family CeMIn5 (M=Co, Rh). References:  J. Custers et al., Nature 424, 524 (2003); J. Custers et al., Phys. Rev. Lett. 104, 186402 (2010).  Yung-Yeh Chang, Silke Paschen, and Chung-Hou Chung, Phys. Rev. B 97, 035156 (2018).  Y. Y. Chang,, F. Hsu, S. Kirchner, C. Y. Mou, T. K. Lee and C. H. Chung (un-published).
Hosted by: Alexei Tsvelik
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