Department of Physics
Condensed Matter Seminar

Helical fermi liquids (HLFL) have momentum dependent spin or pseudospin alignments at the fermi surface, which can be applied to systems with spin-orbital couplings, for instance the edge states of topological band insulators. We study quantum phase transitions associated with spontaneous symmetry breaking in HLFL. According to the stanford Hertz-Millis theory, for ordinary fermi liquid, the quantum critical modes are usually over-damped due to low energy particle-hole excitations, which lead to nonrelativistic universality class. For HLFL, due to the special spin alignment at the fermi surface, part of the quantum critical modes decouple from the particle-hole excitation in the infrared limit, and the nature of the transition in general differs from the Hertz-Millis theory.