Calendário de Eventos

Colóquio da Pós-Graduação - Dr. Aline Ramires (Paul Scherrer Institute, Switzerland) e Dr. Yasuhiro Tada (Institute for Solid State Physics, University of Tokyo - Japan)
Quinta-feira, Dezembro 10, 2020, 08:30
por Luciana Vechi de Carvalho
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SCES Webinar Series

"Stabilizing even-parity chiral superconductivity in Sr2RuO4".

Dr. Aline Ramires (Paul Scherrer Institute, Switzerland)

Strontium ruthenate (Sr2RuO4) has long been thought to host a spin-triplet chiral p-wave superconducting state. However, the singlet-like response observed in recent spin-susceptibility measurements casts serious doubts on this pairing state. Together with the evidence for broken time-reversal symmetry and a jump in the shear modulus c66 at the superconducting transition temperature, the available experiments point towards an even-parity chiral superconductor with kz(kx ± iky)-like Eg symmetry, which has consistently been dismissed based on the quasi-two-dimensional electronic structure of Sr2RuO4. Here, we show how the orbital degree of freedom can encode the two-component nature of the Eg order parameter, allowing for a local orbital-antisymmetric spin-triplet state that can be stabilized by on-site Hund’s coupling. We find that this exotic Eg state can be energetically stable once a complete, realistic three-dimensional model is considered, within which momentum-dependent spin-orbit coupling terms are key.


"Quantum criticality of magnetic field induced order in a correlated Dirac semimetal"

Dr. Yasuhiro Tada (Institute for Solid State Physics, University of Tokyo - Japan)

Recently, there have emerged various candidate materials of strongly correlated Dirac semimetals. Theoretically, it is known that such Dirac semimetals can show characteristic quantum criticalities which are distinct from the conventional criticalities of bosonic order parameters. Furthermore, the Landau quantization can enhance the symmetry breaking in presence of a magnetic field, which is called magnetic catalysis.

In this study, we investigate quantum criticality of the magnetic-field-induced charge density wave (CDW) order in a simple model of correlated spinless Dirac fermions at zero temperature as a prototypical example of the magnetic catalysis, by using the infinite density matrix renormalization group. It is found that the CDW order parameter M(B) exhibits an anomalous magnetic field (B) scaling behavior characteristic of the (2+1)-dimensional chiral Ising universality class near the quantum critical point, which leads to a strong enhancement of M(B) compared with a mean-field result. We also establish a global phase diagram in the interaction-magnetic field plane for the fermionic quantum criticality.


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