Nematic quantum phase transition induced by transverse fields in strongly correlated electron systems

Abstract

We describe here the main physical properties of unconventional high-temperature superconductors containing iron in their structures, the so-called iron-based superconductors (FeSCs). The phase diagram of these materials exhibits a plethora of collective fluctuations besides superconductivity, which includes a long range magnetic ordering of the stripe-type and also nematic order. In most of the FeSCs, both magnetic and nematic phases coexist for a large range of doping and disappear at a putative quantum critical point (QCP) under the superconducting dome. As recently pointed out in the literature, these features of the phase diagram of the FeSCs can be captured by orbital-projected band models, which takes into account the fermionic degrees of freedom near the Fermi pockets and the orbital content of the interactions. We also discuss here the issues to address the role of quantum nematic fluctuations for the formation of unconventional pairing states in FeSCs. In particular, we mention the recent theoretical proposal by Maharaj and collaborators [arXiv:1704.07841 (2017)] of using transverse fields (for instance, shear strain or perpendicular magnetic field) to continuously tune the nematic QCP by enhancing the nematic quantum fluctuations. This leads us to propose in this BEPE post-doc project the investigation of the critical properties for an effective theory of an orbital-projected band model subjected to transverse fields. The methodology here will be based on the application of Landau-Ginzburg analysis and the field-theoretical renormalization group method. The last topics of this project include the schedule for its implementation, the way we disseminate the results and, finally, the corresponding references. (AU)