New Electronic Phase Transitions in \alpha-(BEDT-TTF)2KHg(SCN)4

TL;DR

This paper reports new magnetic field-induced charge-density-wave transitions in -(BEDT-TTF)2KHg(SCN)4, revealing complex interplay between CDW, superconductivity, and magnetic effects under pressure and tilted magnetic fields.

Contribution

It introduces a novel type of field-induced CDW transitions driven by combined Pauli and orbital magnetic effects, and explores their coexistence with superconductivity under pressure.

Findings

Identification of field-induced CDW transitions at pressures above critical pressure.

Discovery of a new FICDW transition mechanism influenced by magnetic field tilt.

Observation of superconductivity coexisting with CDW, with increased transition temperature.

Abstract

\alpha-(BEDT-TTF)2KHg(SCN)4 is considered to be in the charge-density-wave (CDW) state below 8 K. We present new magnetoresistance data suggesting that the material undergoes a series of field-induced CDW (FICDW) transitions at pressures slightly exceeding the critical pressure Pc at which the zero-field CDW state is destroyed. Further, we argue that a novel kind of FICDW transitions, entirely determined by a superposition of the strong Pauli and quantizing orbital effects of magnetic field on the CDW wavevector, arises when the field is strongly tilted towards the conducting layers. These new transitions can take place even in the case of a relatively well nested Fermi surface. Finally we report on the superconducting (SC) state and its coexistence with the CDW in the title compound under quasi-hydrostatic pressure. Below Pc the material is most likely a heterogeneous SC/CDW mixture, with the SC phase persisting down to ambient pressure. The SC onset temperature appears to drastically increase upon entering the SC/CDW coexistence region.