Quantum phase transitions in electronic systems

Abstract

Quantum phase transitions occur at zero temperature when some non‐thermal control‐parameter like pressure or chemical composition is changed. They are driven by quantum rather than thermal fluctuations. In this review we first give a pedagogical introduction to quantum phase transitions and quantum critical behavior emphasizing similarities with and differences to classical thermal phase transitions. We then illustrate the general concepts by discussing a few examples of quantum phase transitions occurring in electronic systems. The ferromagnetic transition of itinerant electrons shows a very rich behavior since the magnetization couples to additional electronic soft modes which generates an effective long‐range interaction between the spin fluctuations. We then consider the influence of rare regions on quantum phase transitions in systems with quenched disorder, taking the antiferromagnetic transitions of itinerant electrons as a primary example. Finally we discuss some aspects of the metal‐insulator transition in the presence of quenched disorder and interactions.

Structural and physical properties of Ni 1−x V x alloys around and away from quantum critical point

“…Theoretically, the linear behaviour has been shown by the work of Hertz and Millis [41,62]. The electrical transport in this region is strongly influenced by the critical fluctuations [63] of the order parameter, leading to the deviations from the Fermi-liquid behaviour. In the present study, the deviation from Fermi liquid behaviour could be due to the behaviour of the Griffiths exponent in the compositions around qcp in the low temperature limit.…”

Finite temperature quantum condensations in the space of states: general proof

“…The expression 'quantum phase transitions' (QPTs) [1][2][3][4][5][6] usually refers to phase transitions occurring at zero temperature (T = 0): in contrast to classical phase transitions, which are driven by the temperature, QPTs are meant to be driven by varying some Hamiltonian parameter of the system. Such a definition, however, might be a bit misleading.…”