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Taka Shibauchi - Department of Physics, Kyoto University

Quantum criticality tuned by dimensionality in a heavy fermion antiferromagnet


The coexistence of low dimensionality and strong electron-electron Coulomb interaction often sets the stage for the emergence of novel states of condensed matter. The high-temperature superconductivity and fractional quantum Hall effect are perhaps the most dramatic among such examples. Metallic systems with the strongest electron correlations are realized in certain rare-earth and actinide compounds whose physics are dominated by f-electrons. These materials are known as heavy fermions, so called because the effective mass of the conduction electrons are enhanced via correlation effects up to as much as several hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. Confinement of the heavy-fermions to reduced dimensions is expected to provide a novel physical system with ultimately strong correlations and enhanced quantum fluctuations.

 

Here we report on the first realization of a two-dimensional heavy-fermion system, where the dmensionality is adjusted in a controllable fashion by fabricating heterostructures which are unavailable in nature. Artificial superlattices of antiferromagnetic heavy-fermion compound CeIn_3 with a Neel temperature T_N=10 K and conventional metal LaIn_3 are grown epitaxially by molecular beam epitaxy. We find that by reducing the CeIn_3 layer thickness the magnetic order is suppressed and finally disappears at two-unit-cell thickness. The heavy-fermions in the flatland display striking deviations from the standard behaviors of Landau’s Fermi-liquid in the electronic properties at low temperatures, associated with a new dimensional tuning of quantum criticality.

 

H. Shishido, T. Shibauchi, K. Yasu, T. Kato, H. Kontani, T. Terashima, and Y. Matsuda, Science 327, 980-983 (2010).

 

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