Recent Advances in Unconventional Density Waves

TL;DR

This paper reviews recent theoretical and experimental advances in unconventional density waves (UDW), highlighting their role in explaining phenomena like the pseudogap phase in high-temperature superconductors and properties of certain organic conductors.

Contribution

It demonstrates that many properties of the low temperature phase in specific organic conductors can be explained by unconventional charge density waves using mean field theory.

Findings

Landau quantization explains angular dependent magnetoresistance.

Negative giant Nernst effect is a hallmark of UDW.

Properties of alpha-(BEDT-TTF)_2MHg(SCN)_4 are characterized by UCDW.

Abstract

Unconventional density wave (UDW) has been speculated as a possible electronic ground state in excitonic insulator in 1968. Recent surge of interest in UDW is partly due to the proposal that the pseudogap phase in high T_c cuprate superconductors is d-wave density wave (d-DW). Here we review our recent works on UDW within the framework of mean field theory. In particular we have shown that many properties of the low temperature phase (LTP) in alpha-(BEDT-TTF)_2MHg(SCN)_4 with M=K, Rb and Tl are well characterized in terms of unconventional charge density wave (UCDW). In this identification the Landau quantization of the quasiparticle motion in a magnetic field (the Nersesyan effect) plays the crucial role. Indeed the angular dependent magnetoresistance and the negative giant Nernst effect are two hallmarks of UDW.