THERMODYNAMIC DETECTION OF QUANTUM PHASE TRANSITIONS

FRANCESCO IACHELLO

Sergei M. Stishov

Michael Kruse, H. G. Miller, Angelo Plastino +1 more

We show that, by recourse to thermodynamics's third law, quantum phase transitions in a system of fermions can be detected, in the sense that thereby one automatically finds the values of the external parameter (here coupling strengths of the pertinent Hamiltonian) at which these transitions occur. We illustrate our considerations with reference to an exactly solvable model of Plastino and Moszkowski [Il Nuovo Cimento 47, 470 (1978)].

A. P. Young

Dieter Suter, Alexander Pines

The behaviour of quantum mechanical state functions under selective rotations is discussed.If a two level transition is phase-shifted with composite z-pulses, the component state function shared with a connected transition can be multiplied by i, thereby shifting the corresponding coherence into an orthogonal channel.Application to the sensitive indirect detection of NMR .transitions is demonstrated.