Producción CyT
Congreso
Autoría
GRANADA, MARA
;
D. Lucot
;
R. Giraud
;
A. Lemaître
;
C. Ulysse
;
X. Waintal
;
G. Faini
Fecha
2013
Editorial y Lugar de Edición
LAW3M
Resumen
Información suministrada por el agente en
SIGEVA
A quantum system undergoing an adiabatic evolution accumulates a geometrical phase, which adds to the standard dynamical phase. This phase, introduced by Berry in his 1984 seminal paper, has become a central concept in our understanding of quantum mechanics. In condensed matter, the Berry phase is intimately related to band theory. It provides a deep understanding of, say, the topological nature of quantum Hall effect or some peculiar features of graphene. Despite its fundamental nature, no dir...
A quantum system undergoing an adiabatic evolution accumulates a geometrical phase, which adds to the standard dynamical phase. This phase, introduced by Berry in his 1984 seminal paper, has become a central concept in our understanding of quantum mechanics. In condensed matter, the Berry phase is intimately related to band theory. It provides a deep understanding of, say, the topological nature of quantum Hall effect or some peculiar features of graphene. Despite its fundamental nature, no direct experimental signatures have been reported, except through reinterpretation of anomalous Hall-related effects. Here, we report on experimental evidences of a Berry phase accumulated by the quasi-particle (hole) wave function in a mesoscopic device made from a ferromagnetic semiconductor (Ga,Mn)(As,P) layer. Its signature is revealed as unusual patterns in the universal conductance fluctuations (UCF), which arise from quantum interferences between different electronic trajectories in disordered materials. Such patterns had been observed previously [1,2], and the presence of domain walls was thought to be their cause. More recently, a theoretical work proposed that a Berry phase, rather than domain walls, is at the origin of this effect [3]. Magnetotransport experiments were carried at low temperatures (T<1 K), carefully controlling the absence of domain walls. The temperature dependence of the amplitude and quasi-period of the conductance fluctuations, indicate that these patterns are related to a change of the Berry phase as the magnetization direction is rotated and quantum interference is the tool to detect this phase. Hence, (Ga,Mn)As appears as a very interesting test bench for new concepts based on this geometrical phase. [1] L. Vila et al., Phys. Rev. Lett. 98, 027204 (2007). [2] K. Wagner et al., Phys. Rev. Lett. 97, 056803 (2006). [3] K. M. D. Hals et al., Phys. Rev. Lett. 105, 207204 (2012).
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Palabras Clave
MESOSCOPIC TRANPORTDILUTED MAGNETIC SEMICONDUCTORSBERRY PHASE