Effective masses in a strongly anisotropic Fermi liquid

TL;DR

This paper investigates how anisotropic quasiparticle residues affect effective masses in a Fermi liquid, explaining large cyclotron masses in underdoped cuprates through a model with angle-dependent Z_q.

Contribution

It introduces a phenomenological model linking anisotropic Z_q to effective masses, clarifying experimental observations in cuprates.

Findings

Cyclotron mass is enhanced by <1/Z_q> in anisotropic Fermi liquids.

Infrared Hall mass depends on <Z_q> / <Z_q^2>, can remain small.

Small Z_q regions lead to large cyclotron masses while Hall mass stays modest.

Abstract

Motivated by the recent experimental observation of quantum oscillations in the underdoped cuprates, we study the cyclotron and infrared Hall effective masses in an anisotropic Fermi liquid characterized by an angle-dependent quasiparticle residue Z_q, which models an arc-shaped Fermi surface. Our primary motivation is to explain the relatively large value of the cyclotron effective mass observed experimentally and its relation with the effective Hall mass. In the framework of a phenomenological model of an anisotropic Fermi liquid, we find that the cyclotron mass is enhanced by a factor <1/Z_q>, while the effective Hall mass is proportional to <Z_q> / <Z_q^2>, where <...> implies an averaging over the Fermi surface. We conclude that if the Z-factor becomes small in some part of the Fermi surface (e.g., in the case of a Fermi arc), the cyclotron mass is enhanced sharply while the infrared Hall mass may remain small. Possible future experiments are discussed.