Dr. Nirmal J. Ghimire
Argonne National Lab
A quantum phase transition occurs at absolute zero temperature as a consequence of the quantum fluctuations guaranteed by the Heisenberg uncertainty principle. Generally, a quantum critical point (QCP) can be reached by driving magnetic or other type of order to absolute zero [1]. Exot- ic phenomena like unconventional superconductivity and non-Fermi liquid behavior are often found in the vicinity of the QCP, thus making the quantum critical region a potential area to search for new electronic properties. Ce-based heavy fermion compounds provide a fascinating playground to study such behavior. The small energy scales (~10 K) of competing Kondo and RKKY interactions in these materials make it relatively easy to access the QCP by suppressing the magnetic order down to the zero temperature using an external parameter, such as magnetic field, pressure or chemical doping. Experiments suggest that reducing the dimensionality of the Ce-4f electrons may control a route to the QCP [2] and may also change the character of the quantum fluctuations. In bulk materials, this type of dimensional tuning can be achieved, to some extent, in layered crystals. In this talk I will discuss our recent approach in searching for quantum criticality in the layered Ce-based heavy fermion compounds. In particular, I will present the properties of newly discovered compounds CeMAl4Si2 (M=Rh, Ir) [3-6], and Ce2PdAl7Ge4 [7]. CeMAl4Si2 (M=Rh, Ir), n = 1 members of the CeMnAl2n+2Si2 family, show a quasi 2D electronic behavior and an incommensurate to commensurate antiferromagnetic transition. Ce2PdAl7Ge4 has a more two 2D Fermi surface. It manifests a non-Fermi liquid behavior possibly due to a nearby QCP.
References:
[1] O. Stockert and F. Steglich, Annu. Rev. Condens. Matter Phys. 2, 79 (2011). [2] H. Shishido et. al., Science 327, 980 (2010).
[3] N. J. Ghimire et. al., J. Phys.: Condens. Matter 27, 499501 (2015).
[4] N. J . Ghimire et. al., J. Phys.: Condens. Matter 27, 245603 (2015).
[5] H. Sakai et. al., Phys. Rev. B 93, 014402 (2016).
[6] J. Gunasekera, et. al., arXiv:1509.020902 (2015). [7] N. J. Ghimire et. al., submitted.
Read More