hello Francesco
here a small update of your code and the result
see the line where I defined the number of ticks for colorbar
T1 = readtable('SLJ20 PEEL.xlsx', 'VariableNamingRule','preserve');
% First10Rows = T1(1:10,:)
% T1Sz = size(T1)
VarNames = T1.Properties.VariableNames;
N = 50; % Interpolation Matrix Size
xv = linspace(min(T1{:,1}), max(T1{:,1}), N); % Create Vector
yv = linspace(min(T1{:,2}), max(T1{:,2}), N); % Create Vector
[Xm,Ym] = ndgrid(xv,yv); % Create Interpolation Matrices
Zm = griddata(T1{:,1}, T1{:,2}, T1{:,3}, Xm, Ym); % Interpolate
figure
surfc(Xm, Ym, Zm)
grid on
shading interp
set(0, 'DefaultTextInterpreter', 'latex')
hcb = colorbar;
xlabel(hcb,'[{\it Pa}]');
hcb.Label.Interpreter = 'latex';
set(hcb,'TickLabelInterpreter','latex')
colormap(jet(50))
title ('EPX1','FontSize',13,'interpreter', 'latex')
set(0, 'DefaultTextInterpreter', 'latex')
hcb = colorbar;
hcb.TickLabelInterpreter='latex';
ColorbarRulerProperties = hcb.Ruler
hcb.Ruler.TickLabelFormat = '%.2f';
% set(hcb, 'Ticks', sort([hcb.Limits, hcb.Ticks]))
%%%%%%%%%%%%
Nticks = 10; % define number of ticks displayed in colorbar
aa = hcb.Limits;
CBAR_ticks = linspace(aa(1),aa(2),Nticks);
set(hcb, 'Ticks', CBAR_ticks);
%%%%%%%%%%%%
set(gca,'TickLabelInterpreter','latex')
% tix = hcb.Ticks;
% expstr = @(x) [x(:).*10.^ceil(-log10(abs(x(:)+(x==0)))) floor(log10(abs(x(:)+(x==0))))];
% tixexp = expstr(tix(:))
% tixexplbl = compose('%.2f \\times 10^{%2d}',[tixexp(:,1) fix(tixexp(:,2))])
% hcb.TickLabels = tixexplbl;
xlabel('{\it x} [{\it mm}]')
ylabel('{\it y} [{\it mm}]')
zlabel('{\it} Shear stress [{\it MPa}]')
