Quantum matter in high magnetic fields

Research group

Research theme

Sub department

About

Quantum Oscillation Studies of the Fermi Surface of LaFePO

(2009)

Authors:

A Carrington, AI Coldea, JD Fletcher, NE Hussey, CMJ Andrew, AF Bangura, JG Analytis, J-H Chu, AS Erickson, IR Fisher, RD McDonald

Fermi surface of superconducting LaFePO determined from quantum oscillations.

Phys Rev Lett 101:21 (2008) 216402

Authors:

AI Coldea, JD Fletcher, A Carrington, JG Analytis, AF Bangura, J-H Chu, AS Erickson, IR Fisher, NE Hussey, RD McDonald

Abstract:

We report extensive measurements of quantum oscillations in the normal state of the Fe-based superconductor LaFePO, (T(c) approximately 6 K) using low temperature torque magnetometry and transport in high static magnetic fields (45 T). We find that the Fermi surface is in broad agreement with the band-structure calculations with the quasiparticle mass enhanced by a factor approximately 2. The quasi-two-dimensional Fermi surface consists of nearly nested electron and hole pockets, suggesting proximity to a spin or charge density wave instability.

Fermi surface of superconducting LaFePO determined by quantum oscillations

(2008)

Authors:

AI Coldea, JD Fletcher, A Carrington, JG Analytis, AF Bangura, J-H Chu, AS Erickson, IR Fisher, NE Hussey, RD McDonald

Angle-dependent magnetoresistance oscillations due to magnetic breakdown orbits

Physical Review B - Condensed Matter and Materials Physics 76:5 (2007)

Authors:

AF Bangura, PA Goddard, J Singleton, SW Tozer, AI Coldea, A Ardavan, RD McDonald, SJ Blundell, JA Schlueter

Abstract:

We present experimental evidence for a hitherto unconfirmed type of angle-dependent magnetoresistance oscillation caused by magnetic breakdown. The effect was observed in the organic superconductor 魏- (BEDT-TTF)2 Cu (NCS)2 using hydrostatic pressures of up to 9.8 kbar and magnetic fields of up to 33 T. In addition, we show that similar oscillations are revealed in ambient-pressure measurements, provided that the Shubnikov-de Haas oscillations are suppressed either by elevated temperatures or filtering of the data. These results provide a compelling validation of Pippard's semiclassical picture of magnetic breakdown. 漏 2007 The American Physical Society.

Persistence to high temperatures of interlayer coherence in an organic superconductor.

Phys Rev Lett 99:2 (2007) 027004

Authors:

John Singleton, PA Goddard, A Ardavan, AI Coldea, SJ Blundell, RD McDonald, S Tozer, JA Schlueter

Abstract:

The interlayer magnetoresistance rho(zz) of the organic metal kappa-(BEDT-TTF)(2)Cu(NCS)(2) is studied in fields of up to 45 T and at temperatures T from 0.5 to 30 K. The peak in rho(zz) seen in in-plane fields, a definitive signature of interlayer coherence, remains to Ts exceeding the Anderson criterion for incoherent transport by a factor approximately 30. Angle-dependent magnetoresistance oscillations are modeled using an approach based on field-induced quasiparticle paths on a 3D Fermi surface, to yield the T dependence of the scattering rate tau(-1). The results suggest that tau(-1) does not vary strongly over the Fermi surface, and that it has a T(2) dependence due to electron-electron scattering.