TY  - JOUR
A1  - Nemati, Somayyeh
A1  - Henkel, Carsten
A1  - Anders, Janet
T1  - Coupling function from bath density of states
JF  - epl : a letters journal exploring the frontiers of physics
N2  - Modelling of an open quantum system requires knowledge of parameters that specify how it couples to its environment. However, beyond relaxation rates, realistic parameters for specific environments and materials are rarely known. Here we present a method of inferring the coupling between a generic system and its bosonic (e.g., phononic) environment from the experimentally measurable density of states (DOS). With it we confirm that the DOS of the well-known Debye model for three-dimensional solids is physically equivalent to choosing an Ohmic bath. We further match a real phonon DOS to a series of Lorentzian coupling functions, allowing us to determine coupling parameters for gold, yttrium iron garnet (YIG) and iron as examples. The results illustrate how to obtain material-specific dynamical properties, such as memory kernels. The proposed method opens the door to more accurate modelling of relaxation dynamics, for example for phonon-dominated spin damping in magnetic materials.
Y1  - 2022
U6  - https://doi.org/10.1209/0295-5075/ac7b42
SN  - 0295-5075
SN  - 1286-4854
VL  - 139
IS  - 3
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Fumani, F. Khastehdel
A1  - Nemati, Somayyeh
A1  - Mahdavifar, Saeed
T1  - Quantum critical lines in the ground state phase diagram of spin-1/2 frustrated transverse-field ising chains
JF  - Annalen der Physik
N2  - This paper focuses on the ground state phase diagram of a 1D spin-1/2 quantum Ising model with competing first and second nearest neighbour interactions known as the axial next nearest neighbour Ising model in the presence of a transverse magnetic field. Here, using quantum correlations, both numerically and analytically, some evidence is provided to clarify the identification of the ground state phase diagram. Local quantum correlations play a crucial role in detecting the critical lines either revealed or hidden by symmetry-breaking. A non-symmetry-breaking disorder transition line can be identified by the first derivative of both entanglement of formation and quantum discord between nearest neighbour spins. In addition, the quantum correlations between the second neighbour spins can also be used to reveal Kosterlitz-Thouless phase transition when their interaction strength grows and becomes closer to the first nearest neighbour one. The results obtained using the Jordan-Wigner transformation confirm the accuracy of the numerical case.
KW  - axial next nearest neighbour Ising chains
KW  - quantum correlations
KW  - quantum
KW  - phase transitions
Y1  - 2020
U6  - https://doi.org/10.1002/andp.202000384
SN  - 0003-3804
SN  - 1521-3889
VL  - 533
IS  - 2
PB  - Wiley-VCH
CY  - Weinheim
ER  -