scholarly journals Quantum fidelity for degenerate ground states in quantum phase transitions

2013 ◽  
Vol 88 (3) ◽  
Author(s):  
Yao Heng Su ◽  
Bing-Quan Hu ◽  
Sheng-Hao Li ◽  
Sam Young Cho
Keyword(s):  
Phase Transitions ◽  
Quantum Phase Transitions ◽  
Ground States ◽  
Quantum Phase ◽  
Quantum Fidelity

scholarly journals Quantum fidelity susceptibility in excited state quantum phase transitions: application to the bending spectra of nonrigid molecules

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Jamil Khalouf-Rivera ◽  
Miguel Carvajal ◽  
Francisco Perez-Bernal
Keyword(s):  
Phase Transitions ◽  
Excited State ◽  
Molecular Species ◽  
Quantum Phase Transitions ◽  
Quantum Phase ◽  
The Other ◽  
Two Dimensional ◽  
Nonrigid Molecules ◽  
Bending Modes ◽  
Quantum Fidelity

We characterize excited state quantum phase transitions in the two dimensional limit of the vibron model with the quantum fidelity susceptibility, comparing the obtained results with the information provided by the participation ratio. As an application, we locate the eigenstate closest to the barrier to linearity and determine the linear or bent character of the different overtones for particular bending modes of six molecular species. We perform a fit and use the optimized eigenvalues and eigenstates in three cases and make use of recently published results for the other three cases.

scholarly journals The Loschmidt Index

2021 ◽  
Vol 10 (5) ◽  
Author(s):  
Diego Liska ◽  
Vladimir Gritsev
Keyword(s):  
Phase Transitions ◽  
Integral Representation ◽  
Quantum Phase Transitions ◽  
Ground States ◽  
Quantum Phase ◽  
Xy Model ◽  
Parameter Dependent ◽  
The Relationship ◽  
Multi Band

We study the nodes of the wavefunction overlap between ground states of a parameter-dependent Hamiltonian. These nodes are topological, and we can use them to analyze in a unifying way both equilibrium and dynamical quantum phase transitions in multi-band systems. We define the Loschmidt index as the number of nodes in this overlap and discuss the relationship between this index and the wrapping number of a closed auxiliary hypersurface. This relationship allows us to compute this index systematically, using an integral representation of the wrapping number. We comment on the relationship between the Loschmidt index and other well-established topological numbers. As an example, we classify the equilibrium and dynamical quantum phase transitions of the XY model by counting the nodes in the wavefunction overlaps.

scholarly journals GROUND STATES OF A MIXTURE OF TWO SPECIES OF SPIN-1 BOSE GASES WITH INTERSPECIES SPIN EXCHANGE IN A MAGNETIC FIELD

2012 ◽  
Vol 26 (01) ◽  
pp. 1250002 ◽  
Author(s):  
YU SHI ◽  
LI GE
Keyword(s):  
Magnetic Field ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Spin Exchange ◽  
Quantum Phase Transitions ◽  
Ground States ◽  
Total Spin ◽  
Quantum Phase ◽  
Spin Coupling ◽  
The Magnetic Field

We consider a mixture of two species of spin-1 atoms with both interspecies and intraspecies spin exchanges in a weak magnetic field. Under the usual single mode approximation, it can be reduced to a model of coupled giant spins. We find most of its ground states. This is a complicated problem of energy minimization, with three quantum variables under constraints, i.e., the total spin of each species and the total spin of the whole mixture, as well as four parameters, including intraspecies and interspecies spin coupling strengths and the magnetic field. The quantum phase diagram is very rich. Compared with the case without a magnetic field, the ground states are modified by a magnetic field, which also modifies the ground state boundaries or introduces new crossover regimes on the phase diagram. Without interspecies spin coupling, the quantum phase transitions existing in absence of a magnetic field disappear when a magnetic field is applied, which leads to crossover regimes in the phase diagram. Under ferromagnetic interspecies spin coupling, the ground states remain disentangled no matter whether there is a magnetic field. For antiferromagnetic interspecies spin coupling, a magnetic field entangles the ground states in some parameter regimes. When the intraspecies spin couplings are both ferromagnetic, the quantum phase transition between antiferromagnetic and zero interspecies spin couplings survives the magnetic field. When the intraspecies spin couplings are both antiferromagnetic, a magnetic field induces new quantum phase transitions between antiferromagnetic and zero interspecies spin couplings.

scholarly journals Diversity of quantum ground states and quantum phase transitions of a spin- 12 Heisenberg octahedral chain

2017 ◽  
Vol 95 (22) ◽  
Author(s):  
Jozef Strečka ◽  
Johannes Richter ◽  
Oleg Derzhko ◽  
Taras Verkholyak ◽  
Katarína Karľová
Keyword(s):  
Phase Transitions ◽  
Quantum Phase Transitions ◽  
Ground States ◽  
Quantum Phase ◽  
Quantum Ground States

Quantum phase transitions

2004 ◽  
Vol 174 (8) ◽  
pp. 853 ◽  
Author(s):  
Sergei M. Stishov
Keyword(s):  
Phase Transitions ◽  
Quantum Phase Transitions ◽  
Quantum Phase

scholarly journals Magnetic Field- and Pressure-Induced Quantum Phase Transitions in NH4CuCl3

2005 ◽  
Vol 159 ◽  
pp. 241-245 ◽  
Author(s):  
Masashi Fujisawa ◽  
Budhy Kurniawan ◽  
Toshio Ono ◽  
Hidekazu Tanaka
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Quantum Phase Transitions ◽  
Quantum Phase

scholarly journals Interaction between Different Kinds of Quantum Phase Transitions

2021 ◽  
Vol 3 (2) ◽  
pp. 253-261
Author(s):  
Angel Ricardo Plastino ◽  
Gustavo Luis Ferri ◽  
Angelo Plastino
Keyword(s):  
Phase Transitions ◽  
Nuclear Physics ◽  
Body Problem ◽  
Quantum Phase Transitions ◽  
Quantum Phase ◽  
Exactly Solvable Models ◽  
Solvable Models ◽  
Many Body ◽  
Pairing Interaction ◽  
Exactly Solvable

We employ two different Lipkin-like, exactly solvable models so as to display features of the competition between different fermion–fermion quantum interactions (at finite temperatures). One of our two interactions mimics the pairing interaction responsible for superconductivity. The other interaction is a monopole one that resembles the so-called quadrupole one, much used in nuclear physics as a residual interaction. The pairing versus monopole effects here observed afford for some interesting insights into the intricacies of the quantum many body problem, in particular with regards to so-called quantum phase transitions (strictly, level crossings).

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